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4 Humans in coastal systems.

1. Human settlement of coastal areas

1.1 Human colonization of the coastline

Coastal areas have long provided the human race with such a wonderful variety and quantity of resources that they have been preferred sites for settlements, except for some areas with particularly negative features (health risks, inclement climate, etc.) that did not provide minimum levels of comfort or resources. Coastlines, above all in deltaic and estuarine areas, are very productive areas and humans, from the Neolithic era onwards, have consolidated a model of forced production of resources with far-reaching consequences.

Deltas and the shores of estuaries have always been favored places for human settlement, initially because of their abundant game and fish, and later on because the conditions there favored highly-productive agriculture based on irrigation. Deltas, in particular the Nile delta and lower Mesopotamia, were the birthplace of the earliest human civilizations. This is why these environments have also been at most risk from errors due to mismanagement or misconceived projects instigated by the very people who live there. They have also suffered the consequences of environmental mismanagement far upstream and far inland.

Since colonization of the coastline began, its inhabitants have always sought to make as much use of the nearby fertile muddy marshes and marine environments as the facilities available at the time and the technology then being developed permitted. The first attempts were probably limited to small-scale drainage. Later, large embankments were constructed in low-lying areas, above all in areas below sea level, and also in areas that had subsided below the level of the river beds. These often involved moving very large quantities of earth, and can still be seen in China and the Netherlands.

Lower Mesopotamia

The Tigris and Euphrates rivers join together to form the much fought over Shatt al 'Arab river before flowing into the Persian Gulf. Yet 6,000 years ago, the land the Shatt al 'Arab now flows through did not exist. Or it might be more accurate to say this land was still lying on the steep slopes of the mountains where the two rivers have their headwaters; some of this land might also have come from the slopes of the Zagros Mountains, the source of the Karun and Kharkeh rivers, inputs from which have also contributed to this sediment deposition. The Tigris and Euphrates originally had separate mouths far to the north, with estuaries open to the Persian Gulf, which covered a larger area and was deeper than today. Over thousands of years, however, the progressive deforestation of the watersheds by human action has washed away so much soil, deposited downstream as sediment, that these estuaries have silted up and the coastline of the Persian Gulf has advanced over 124 mi (200 km).

The world's first true urban culture grew up 6,000 years ago on the shores of these estuaries, whose remains are the marshlands of south Iraq, and upstream from what is now the Shatt al 'Arab. This culture developed between 4300-3500 B.C. and is known as the Ubaidian culture after the Tall al 'Ubayd archeological site near the contemporary Iraqi city of Al-Nasiriyah. The Ubaidian cities were self-sufficient in cereals, meat, and milk, and also made use of the vast game and fish supplies in the nearby lakes and marshes. However, food production depended to a large extent on efficient water management, and in particular, on correct use of the various arms of the lower courses of the Tigris and Euphrates rivers. Most remains from this civilization have been found in the oldest levels of the cities of Eridu and Ur on the lower course of the river Euphrates. The Ubaidian people had to perform hydraulic engineering projects, such as digging drainage and irrigation channels to take water where it was needed, if only to restore water supplies to cultivated areas left high and dry by changes in river courses.

Towards the end of the fourth millennium B.C., a little more than 5,000 years ago, the Sumerians settled in Lower Mesopotamia, replacing the Ubaidians, and seem to have been the first humans to have used a script system to express language graphically. They also consolidated the region's advances in hydraulic engineering. Sumerian civilization consisted of citystates permanently fighting for control of the surrounding territory. Their complex social stratification reflected their ability to produce food surpluses and their need to control water supplies. Surplus production by the agricultural sector freed a large part of the population from this task, while controlling water supplies and the maintenance of the irrigation and drainage channels required both technical abilities and an abundant workforce.

A limited number of documents written on clay tablets in the cuneiform characters developed by the Sumerians provide information about life in ancient Mesopotamia, and confirm that maintaining the water network had been important since the remote past. Records of land, canals, irrigation, and drainage ditches were kept. They were built and maintained under the supervision of the city's or kingdom's authorities by means of a system of compulsory labor that no-one could avoid except as a royal privilege. The law established how water was to be distributed between those using it for irrigation, and punished cases of negligence and fraud that might harm the interests of neighbors or the entire community. The law even laid down how accidental losses (floods, landslides, etc.) would be split between the owner and the sharecropper when a piece of land was rented out.

Lower Egypt

The oldest evidence of agriculture in Lower Egypt (the Nile delta) dates from 6,500 years ago. Excavations carried out in Merimbe in the southwest of the Nile delta found the remains of a two-hectare village. Granaries with barley and emmer wheat (Triticum dicoccum) seeds and paved areas resembling threshing floors were found, evidence of relatively developed agriculture that would have complemented an economy further nourished by hunting, fishing, and gathering. Yet unlike Mesopotamia, the first indications of an urban civilization date from after its culmination, which happened at about the same time as the union of Lower Egypt (the Nile delta) with Upper Egypt (the Nile Valley) to form a single state under the absolute rule of the pharaoh, a monarch treated as a living god. Until the first dynasty, 5,200 years ago, the Egyptians had lived in largely autonomous towns with their respective spheres of influence. Egyptian tradition, as yet unconfirmed by archeological evidence, states that before Menes founded the first historical Egyptian dynasty, there were two kingdoms, Lower Egypt and Upper Egypt, which he unified.

The regularity of the Nile's annual floods in the middle of the summer and the input of water and fertile soil meant that early Egyptian agriculture was very different from that of Mesopotamia. Egypt also developed a strict bureaucracy that counted and recorded how many animals each head of family owned and how much land he farmed (all land was nominally owned by the pharaoh). Agricultural surpluses were collected for the pharaoh's granaries and treasury, and were then divided and distributed among the nobility, the priests, and the administrators and workers of the royal household. Provincial governors selected from those closest to the pharaoh's family set up their own households, modest copies of the pharaoh's. A solar calendar was soon developed that made it possible to predict the beneficial Nile floods well in advance.

The Lower Yangtze and the Jiangsu plains

Remains of ancient human settlements have also been found in the delta of the river Yangtze, as well as some of the oldest evidence of rice cultivation in China, dated to around 3400 B.C., although agricultural activity probably goes back even further. Remains of Neolithic fishing communities have also been found all along the former coastline of Jiangsu, between the former mouth of the Yellow (Hoang-Hai) river and the mouth of the Yangzte river. No evidence of hydraulic engineering on a par with Mesopotamia and Egypt has been discovered and it seems that rice was planted in southern China until relatively recently by hand anywhere naturally prone to flooding. Zhou Qu-fei, a learned author of the 12th century A.D., explained in his book Ling-wai taita that southern Chinese peasants did no more than choose "only those lands flooded from the end of one year to the next ... and simply sow the [rice] seeds, they do not transplant the seedlings ... or irrigate the fields when they are dry, nor do they drain the water if it rains too much ... everything is left to the will of heaven." The region's first cities were apparently agglomerations linked to the salt trade, rather than agricultural centers. During the times of the Qin and the first Han Emperors, a little over 2,000 years ago, prosperous salt pans were in operation around the city of Yancheng (literally "salt city"), which is now 31 mi (50 km) inland from the coast of the Yellow Sea.

The development of the first Chinese Neolithic civilization, upwater of the Yellow river, had effects on what are now the Jiangsu coastal plains comparable to the effects that soil erosion in the Fertile Crescent had on Lower Mesopotamia. Over the centuries, the erosion and transport of central China's fragile loess soils by the rivers meant the sea off the Jiangsu coast was known as the Yellow (Hoang-Hai) Sea, because of the immense quantities of sediment it receives. The Yangtze annually discharges around 502 million tonnes of sediment into the Yellow Sea, while the Yellow River discharges around 1,593 million tonnes annually (it now flows into the Bo Hai Sea but has flowed into the Yellow Sea for long periods of its history, most recently from 1938-1947). This is probably less than the values during the periods of maximum erosion and deforestation, so it is not surprising that the coastal plains on the delta of the Yellow Sea grew so rapidly (19 mi [30 km] growth between 1194 and 1855) when both great rivers were flowing into it. Neither is it surprising that the coastline around the Yellow River's former mouth should have retreated since the river changed course to its northern mouth (540.5 sq. mi [1,400 sq. km] lost between 1855 and 1982).

The great Indian deltas

In Bengal, in and amongst the countless arms of the delta of the Ganges and Brahmaputra rivers, farmers have been drying out small parcels of land for perhaps over 3,000 years. Tens of thousands of small plots have been dried out by surrounding them by a small earth dike (und) and the delta is now an immense archipelago of artificial islands. There is evidence of early rice cultivation from the second half of the 4th millennium B.C. in Mahisdal on the northern bank of the Kopai River, in Birbhum District, West Bengal. Likewise, in the west of the Indian subcontinent, in the Narmada and Indus deltas and in the intermediate low-lying areas of the Kutch, the Kathiawar Peninsular, and the Gulf of Khambhat (Cambay), there is evidence of human settlement more than 4,000 years ago, although evidence of agricultural activity is lacking until the Harappa culture arrived in the Indus Valley between 3,500 and 4,000 years ago.

1.2 Modern coastal settlement

The majority of the world's most densely populated areas are in coastal regions. China's coastal provinces occupy 0.58 million sq. mi (1.5 million sq. km)--a little more than 13% of the total surface area of the country--and are inhabited by over 400 million people (approximately 40% of the total population). The coastal states of the United States (excluding Alaska and Hawaii) have 152 million inhabitants (60% of the population) in an area of 1,065,638 [mi.sup.2] (2,760,000 [km.sup.2])--less than 30% of its territory). Eight of the world's ten most populated areas are situated on or near the coast: Tokyo and Yokohama, New York, Los Angeles, Shanghai, and Rio de Janeiro are actually on the coast; Calcutta is on a delta; and Buenos Aires and London are on estuaries. Only a few regions of the world's coasts that are very arid (including the western Sahara, Namibia, the Atacama, and Baja California), cold (the arctic and antarctic coasts, and the extreme tip of South America), or unhealthy (including the Mosquito Coast, the Guyanas, and West Africa) are under-populated or uninhabited.

Human settlements in coastal areas are now so diverse that it is impossible to classify them, even in general terms. The ease of long-distance sea transport has always encouraged all kinds of exchanges between distant coastal communities, often leading to the development of highly cosmopolitan settlements. Usually, coastal settlements are very similar to those of neighboring inland areas, although there are many important exceptions. Resettlement, colonization, migration by sea, and the slave trade, for example, have all populated the world's coastal areas with allochthonous (non-native) peoples. Examples include: northern Europeans in Greenland amongst the Inuit; dark-pigmented Africans on the coast of Guyana and Brazil amongst the indigenous Indian populations; and Chinese in the ports of the Melaka Peninsula, especially Singapore, where they now outnumber the Malays. For this reason, the following discussion of settlement is based on cultural models of resource exploitation that are practiced today or have been practiced historically.

Primitive sedentary hunters and gatherers

Even before the Neolithic age, many coastal areas clearly favored sedentary settlements. Only a few coastal populations have continued hunting and gathering into the 20th century, but in the past most, if not all, were sedentary or at most migrated regularly between winter and summer residences. Today, only the following groups, all sedentary, continue to live mainly by fishing and hunting: the Inuit or Eskimos of the American Arctic, the Chukchi and the Koriak of the coasts of the Euro-Siberia Arctic (those living inland herd reindeer), and some of the people living on the shores of the Okhotsk Sea (the Itelmen of Kamchatka, the Ainu of Hokkaido, the Kurilskiye Ostrova [Kuril islands] and southern Sakhalin, the Quilaks or Nivkh of northern Sakhalin and the mouth of the Amur, the Oroche of easternmost Russia, and the Evenes of the northern shores of the Okhotsk Sea).

The natives of the northwest coast of America came into contact with the southernmost Inuits in western Alaska. These Indians (Eiaks and Tlingits from Alaska, and Wiyots, Yoruks, and Chumashs from what is today California) were culturally advanced with economies based on fishing (above all salmon), hunting of marine mammals, and collecting mollusks and gathering fruits, roots, and other plant resources. Although they were sedentary, they did not practice agriculture except for a few peoples who cultivated tobacco, and they had no domesticated animals (except dogs) until their culture assimilated influences from European settlers in the mid-19th century.

All these cultures, along with the Warau of the Orinoco delta, have been a subject of speculation for social anthropologists who rejected the accepted idea that these hunter-gatherer societies were of necessity nomadic and egalitarian. All these peoples were sedentary and often showed considerable social inequalities, often accentuated by unusual social customs, such as the potlatch of the Kwakiutl and other peoples of the western coast of North America. In the course of this ritual, a person of a superior class showed his status by giving away large quantities of goods and food, challenging others of the same status to hold an even more sumptuous potlatch. This practice was prohibited by the Canadian government in 1884, although the peoples of the region have continued to celebrate potlatches in one form or another ever since, first as a symbol of resistance to British cultural influence, and more recently as a manifestation of a reawakening of Native American culture. These peoples were never very numerous but were among the most culturally and economically developed, as well as densely populated, native Americans before they came into contact with European colonists.

Intensive farmers in delta areas

Sedentary or not, hunting (or fishing) and gathering cultures are the exception in coastal areas. Apart from a few other exceptional cases in arid coastal regions of Africa and Asia (Western Sahara, Somalia, etc.), many coastal populations, and especially those in delta areas, occupy some of the most productive agricultural lands on Earth. The Sumerians of Lower Mesopotamia and the ancient Egyptians of Lower Egypt lived in deltas, whose plentiful water supply could be used to increase harvests and support higher population densities. The deltas were the site of the first intensive changes to the environment, or even conflict with the environment, due to imprudent schemes affecting factors like the regulation of irrigation and drainage water, water eutrophication, land erosion and conservation, soil fertilization, and so on.

Today, the most impressive examples of intensely exploited and densely populated delta areas are still in Egypt (the Nile delta), Bangladesh and neighboring Indian states (the Ganges and Brahmaputra delta), the Chinese coastal plains of Jiangsu between the old mouth (1194-1855) of the Yellow River and the current mouth of the Yangtze, and the Netherlands (Rhine, Meuse, and Schelde delta). The populations of these four areas are totally different. The Nile delta is inhabited principally by Mediterranean peoples, while in the Ganges and Brahmaputra delta, there is a mix of light-and dark-skinned Indians, with a predominance of the former, together with some people of Mongolian origin from the mountains to the east and northeast of the delta. In the Netherlands, the population is predominantly Nordic, although there are a number of groups of people originating from the ex-colonial possessions of Belgium and the Netherlands. In the Jiangsu, the people are exclusively Chinese (central Mongolians). However, all these areas have one thing in common: very high population densities (1,000 people/sq. km in the Nile delta, almost 750 in the Ganges and Brahmaputra delta, over 650 in Jiangsu [excluding Shanghai], and nearly 500 in the Netherlands and the Flemish coastal provinces of Belgium).

Marsh cities

Despite the ever-present threat of natural disasters and those raised by disease-ridden swamps, some of the world's most important cities have been built, against all odds, in the middle or on the banks of coastal lagoons. Venice is the best example, but we should not forget the ancient Sumerian cities, those of the Egypt of the Pharaohs (in the Nile delta), ancient Tartessus (probably), almost all the large cities in the Netherlands, especially Amsterdam, nor the many cities of coastal China, to name but some of them.

Throughout history, administrative, artisanal, and commercial centers of an urban nature have developed alongside highly productive and heavily populated agricultural areas. A consequence of the food and other agricultural surpluses resulting from irrigation, many of these cities' growth was at first stimulated by their strategic location on important sea and river trade routes. Later on, many of these urban areas only survived by industrializing after the city's political power declined or trade routes changed. Alexandria, founded by Alexander the Great in the Nile delta in 332 B.C., was the most important commercial center in Egypt, but lost much trade with the discovery of America in 1492, the development of a route to India around Cape of Good Hope in 1498, and the occupation of Egypt by the Turks. The city did not recover until the opening of the Suez Canal in 1869 and the building of a railway between it and Cairo. Today, Alexandria has a thriving petrochemical sector and many light industries (textiles, food-processing, leather, etc.). Another Mediterranean city, Venice, on the commercial frontier between east and west, was powerful during the Middle Ages but declined from the 15th century onwards after the Turks entered the eastern Mediterranean and when the Spanish and Portuguese began exploring the oceans. The case of Cadiz is different. It was founded by the Phoenicians, possibly in the eighth century B.C., as a commercial base for trade with Tartessus. It maintained its importance under the Roman Empire and only declined under the Muslim Al-Andalus. The discovery of the Americas put Cadiz at the center of the new intercontinental trade routes, and colonial trade enabled it to continue growing until the end of the 19th century. The 20th century has seen Cadiz grow further with the industrialization of the whole of the Bay of Cadiz.

The area around the Bay of Tokyo is the world's largest urban conglomeration. Although it has seen many crises and ups and downs, it has gone through two periods of massive growth separated by one brief period of decadence. No other city has been destroyed and rebuilt as often as Tokyo. The earthquakes of 1633 and 1650 and the fires of 1657 and 1688 gave way to a period of growth during the 17th century. The Tokugawa Dynasty converted Edo, as it was known, into the economic and political center of Japan (it had 150,000 inhabitants in 1613, and 1,300,000 in 1721). With its new name, Tokyo (which means "eastern capital"), it grew even further when Japan was opened up to international trade in the second half of the 19th century. Nevertheless, more tragedies were to hit the city. It was destroyed in 1923 by another earthquake, and again by American bombs between 1944 and 1945. At the end of the Second World War, only three million of the seven million inhabitants living there in 1942 were left. However, between 1945 and 1990 the population increased fourfold and the total population of the conurbation it forms with Yokohama and the other towns around the Bay of Tokyo now exceeds 20 million.

2. The use of plant resources

2.1 The seaweed larder

The diverse and abundant biomass of the seaweeds has been one of the raw materials used since antiquity by people living on the coastal strip. In general the use of seaweeds spread and increased with time, although it was subject to large changes because of the way in which applications developed. The current economic importance of seaweeds derives from two circumstances. The first is the deeply rooted culinary traditions of the countries of the Far East, which provide a large intracultural market that allows for self-sufficiency, and the second factor is the spectacular development of the phycocolloids sector since the Second World War.

The oldest use of seaweeds is as human food. The ancient culinary traditions of some Far Eastern countries, such as Japan, Korea, and China, include the consumption of several species of seaweed, which are still highly appreciated as food. The first written references to this come from Chinese medical materials from the late Zhou dynasty (800-600 B.C.) and some Japanese texts from about 6000 B.C., which considered them "an exquisite plate worthy of the most honored guests." Eighth century A.D. texts from the Japanese court include some seaweeds (Lam-inaria, Undaria, Porphyra, and Gelidium) among the products accepted as payment of imperial tributes. Later, in the 10th century, the oldest Chinese-Japanese dictionary describes the use of several green, brown, and red seaweeds (a total of 21 species) as foodstuffs, explaining the traditional way of preparing them. Since then, but mainly over the last few centuries, there has been evidence of the role that seaweeds play as a basic foodstuff for the coastal settlements in this geographical environment, especially during periods of scarcity of other agricultural products (due to war, famine, etc.).

Gastronomic and nutritional value

Although every zone has its own culinary tradition, the three main ways of preparing seaweeds are raw for direct consumption (garnishes, salads); prepared (dry, freeze-dried, or pre-cooked), for use in the preparation of typical dishes (soups and salads); and gelatins, obtained by boiling the seaweeds, used to make sweets. The seaweed products now on the market are derived from the processing of several species, mainly brown and red seaweeds, often using procedures that go back several centuries. Traditional products, such as nori, kombu, and wakame (obtained respectively from species of Porphyra [red seaweeds with a foliose thallus], the genus Laminaria, and from Undaria pinnatifida, a large phaeophyte), are clear examples of the important process of cultural transmission from generation to generation. Aonori, made using green seaweeds with foliose thalluses (Enteromorpha, Monostroma, and Ulva), and hiziki, made using the brown seaweed Hizikia fusiforme, are the most typical products used in current Japanese cooking, Japan being the world's main consumer of seaweed.

On other continents, such as Europe and America, the development of these culinary traditions was relatively insignificant, and in most cases did not spread beyond the coastal and island cultures where agriculture could not satisfy local requirements, because of the lack of arable land. Dulse is elaborated from the rhodophyte Palmaria palmata and has been consumed since Viking times in Scotland, Ireland, and Iceland, although the most important current market is in the maritime provinces of Canada, mainly Nova Scotia.

Eating seaweeds is related to several of their characteristics, especially taste, texture, and above all their food value. Most seaweeds eaten as food are important sources of essential elements, such as sodium, potassium, phosphorus, magnesium, iodine and trace elements. High iodine intake due to continuous consumption of seaweed has led to the almost total disappearance of goiter in Japan.

The consumption of some seaweeds also represents a considerable intake of vitamins, mainly A, B2, C, and D, as well as other less frequent ones like B1, B12, pantothenic acid, folic acid, and vitamin E. Nori contains more than nine times as much vitamin C as citrus fruits, and for this reason it plays an important role in the nutrition of certain coastal peoples, such as the Inuit.

With respect to their composition, most of a seaweed's dry weight is carbohydrate, although humans can assimilate very little, except in some very specific cases (dulse), with a level of assimilation that is only 60% of that of carbohydrates derived from other plant sources. This is due to the lack of the appropriate enzyme complexes, but even so, populations whose nutrition depends on seaweeds appear to show greater capacity to assimilate them. The quantity of proteins they contain is in general low in comparison with animal-derived foodstuffs, although some species (Porphyra, Palmaria, Ulva, and Undaria) may contain 15-25%. The ability of humans to digest seaweed proteins is limited as with carbohydrates, except in the case of nori (75%), one of the most nutritious foodstuffs derived from seaweeds.

Until the first half of the 20th century, seaweed supply for food use was traditionally based on the exploitation of natural populations, except the supply of Porphyra cultivated by artisanal techniques since the 16th century. The discovery of the life-cycle of these seaweeds (1949-1954) marked the beginning of the industrial development of the modern plant aquaculture that now supplies most of the seaweeds that are used by humans. Although this market is highly localized, the economic importance of seaweed foodstuffs (75% of the world market for seaweeds) far exceeds other uses of seaweed resources.

Husbandry uses

Seaweed is also used as fodder for animals, a minor use in terms of the quantity of seaweed used and its economic importance. Since antiquity intertidal seaweed resources (and the seaweed accumulations found on beaches after storms) have been used as fodder for livestock (cows, horses, goats, sheep, pigs). This activity developed almost entirely in the countries on the Atlantic coast of Europe (France, Scotland, Ireland, Iceland, Norway, and Finland) using several species of phaeophytes (Alaria, Laminaria, Ascophyllum, Fucus, Pelvetia), and a few rhodophytes (Palmaria). Their use has now spread to other coasts where this resource is abundant (such as Canada's maritime provinces) and to neighboring inland settlements, as a consequence of the application of preparation techniques (desiccation or grinding up), which improve their digestibility and allow their regular use as an additional feed that is rich in vitamins and minerals.

Another traditional use of seaweeds is as agricultural fertilizers and soil conditioners. Methods of application include the direct use of whole or ground seaweed, seaweed ash, and the more recent use of commercial liquid extracts (Maxicrop, Alginure, and Seagro) made from mixtures of ground seaweed. The seaweeds used most, especially in Europe, are phaeophytes of the genera Fucus, Laminaria, and Ascophyllum, although many other species are used depending on their availability. Their use is related to their high content of nitrogen and potassium, organic material (which plays a very important role by improving water-retaining capacity and the physical condition of the soil), and with the presence of certain growth factors (auxins, cytokinins, and gibberellins). A special case is that of the calcareous seaweeds of the family Corallinaceae, commonly known by the Breton name maerl; their extremely high calcium carbonate and magnesium carbonate content means they are used as soil conditioners for acid soils. This is practiced in several parts of the world, leading to the extraction of enormous quantities of these seaweeds. In Brittany this reaches a total of 300,000 tons per year.

Industrial uses

Although humans have exploited and used seaweeds for centuries, their introduction into the international market was due to their use by the chemicals industry as a raw material for products such as caustic soda (sodium carbonate), potash (a mixture of potassium salts containing a high percentage of carbonates), and iodine, and later for the extraction of phycocolloids (agars, carrageenans, alginates, etc.).

Caustic soda and potash production from seaweeds The development of the industry extracting caustic soda and potash from the ash of brown seaweeds of the genera Laminaria, Ascophyllum, and Fucus, known as kelps, started in Normandy (France) at the end of the 17th century. The products were for use in glassmaking, ceramics, and soap production. This industry reached its height in the 18th century, when it spread to other neighboring countries (England, Ireland, Norway, and Sweden).

After 1810, the importation of cheaper caustic soda derived from saltpans marked the end of this use for seaweeds. However, Courtois' discovery in 1811 that seaweeds contained iodine led to a revival of the kelp industry that lasted until the end of the century. In 1870, the arrival on the market of iodine derived from the Chilean mineral deposits caused the second and definitive decline in seaweed's industrial applications, although there is evidence for the local production of iodine in Japan and Russia (where it was obtained from a red seaweed, Phyllophora nervosa).

Seaweed production for phycocolloids

The deterioration of commercial relations between the United States and Germany in the years before the First World War led to interest in using different natural resources, such as some kelps (Phaeophyceae), mainly Macrocystis pyrifera, to supply potash and iodine in time of war, as well as some secondary products like acetone and alginin. This production only lasted the duration of the war (1914-1918), but it was the beginning of the industrial extraction of algins some years after (1929). E.C. Stanford in 1880 performed the first scientific research into the gels produced by seaweeds. The discovery of the substances known as algin and carrageenan led to the 20th century development of the phycocolloid industry, based on several natural colloidal products, such as agars, carrageenans, and algins.

The major use of phycocolloids is as food additives, as setting, emulsifying, thickening, and stabilizing agents. Their nutritional value is almost zero, as they are only present in tiny quantities (0.0001-1% by weight) in foodstuffs and they show low digestibility (less than 10%). These and other applications in the field of cosmetics or the pharmaceutical industry show their growing presence in the daily life of developed countries, in addition to their more normal use in microbiology--as a bacterial culture medium--or the more specific restricted use of phycocolloids in biochemistry (electrophoresis, chromatography) and biotechnology (cell culture).

Agar-agar is a mixture of polysaccharides, whose basic monomer is galactose, the main component of the cell wall of some red algae, mainly of the families Gelidiaceae and Gracilariaceae. This phycocolloid has been used since the middle of the 17th century in traditional Japanese cookery (kanten) and began to be used in the west at the end of the 19th century as a culture medium in bacteriology. It developed into an industry after the Second World War, as a consequence of the application of its setting properties in the food industry.

Agar production is now estimated to be about 6,700 tons a year, derived from 50,000 tons of dried seaweeds, most of which are Gelidium (on the coasts of the Iberian peninsula, Morocco, and Japan) and Graciliaria (obtained from the exploitation of areas under concession in Chile).

The term carragheen was given to the gelatins derived from the red seaweeds traditionally consumed by Celtic peoples. Carrageenans are a group of sulphated polysaccharides, polymers of D-galactose, obtained from several red seaweeds, but mainly from natural populations of Chondrus crispus collected in Canada and several species of Gigartina and Iridaea collected in Chile (about 15,000 tons of dry seaweed a year) and Euchema, from large cultivated areas in the Philippines and Indonesia (that produce approximately 66,000 tons a year).

The structure and properties (viscosity, degree of setting) of the carrageenans vary from species to species, and there are even variations between those obtained from the different phases (sporophyte and gametophyte) of a single species. They have a wide range of applications in the food additives industry, in which most carrageenans are consumed.

Algin is a mucilaginous substance formed of alginic acid, a polymer of Dmannuronic and L-galacturonic acids, whose salts with alginic acid are extracted from several species of brown algae. The main genera exploited are Laminaria (50%)--obtained both from natural populations in Norway and France and by cultivation in China--, as well as Ascophyllum (21%), Macrocystis (10%), and Lessonia (10%)--the first mainly collected in Norway, the second in the United States and Mexico, and the third in Chile.

The cultivation of seaweeds and cyanobacteria

The origin of what is now called plant aquaculture goes back to Japan at the end of the 16th century or the beginning of the 17th, and was linked to the production of seaweeds used in the preparation of foodstuffs, mainly nori.

The cultivation of seaweed foodstuffs

The first cultivation of seaweeds of the genus Porphyra began as a consequence of the development of techniques to alleviate the reduction of the traditional collection areas due to natural causes. This technique consisted of planting bamboo branches at a depth of 10-16 ft (3-5 m) in order to favor the natural implantation of the seaweed's spores and their subsequent growth on this substrate. At the end of the 19th century and the beginning of the 20th, the Japanese government had an industrial policy to promote this type of cultivation on most bays along the coastline, with substantial increases in production. Truly industrial development of this crop did not occur until 1930-1970, as the result of a series of technical and scientific advances. These included the replacements of the bamboo bundles by horizontal nets as a new substrate for cultivation (1930); the development of controlled methods for sowing the nets, after the important discovery of the conchocelis stage, the sporophytic generation of Porphyra's life cycle (1949-1954); the introduction of cold storage (-4[degrees]F [-20[degrees]C]) of germinated nets (1960-1970); and the design of the floating cultivation system, with a following spread of cultivation to less polluted zones further from the coast.

In general, the most widespread cultivation method in Japan, China, and Korea, consists of three different phases. The first phase begins in spring and is called conchocelis phase cultivation, and is performed in installations on land; its purpose is to grow and cultivate the filamentous sporophytes. The second phase is the controlled inoculation of the cultivation substrates, which can be performed on dry land or in the aqueous medium and consists of fixing the greatest possible number of conchocelis spores on to the nets; generally attachment is ensured by means of appropriate environmental manipulation of the first phase and the use of cultivation tanks to perform the inoculation. The third phase is the new plant's growth into adult thalluses (a period of 50 days), and takes place in the sea in farms consisting of several units of nets grouped together, which are anchored to the bottom and kept afloat; during this phase a net is harvested several times, and when the small plants appear several nets are frozen as a reserve to make up for the possible losses the crops may suffer.

The estimated annual value of the nori industry is $750 million U.S. dollars, making it one of the world seaweed industry's most important sectors, and it is also one of the most important sectors of the Japanese fishing industry. The rapid development of Porphyra cultivation during the 1950s had a direct effect on the demand for other seaweed products commonly consumed in these countries, such as kombu and wakame, whose production had been based on the exploitation of naturally-occurring seaweed populations.

These programs of cultivation of Undaria pinnatifida and species of Laminaria led to large-scale production of these seaweeds, which has stabilized the availability of the above products. Bearing in mind the similarity between their life cycles, cultivation methods for the two seaweeds are basically the same three phases. The first, obtaining the small plants, is performed in greenhouses during the summer, and consists of growing the microscopic gametophytic phase from the motile sperms attached to appropriate collectors (plastic filaments placed on frames). The collectors are then placed in cultivation tanks with appropriate conditions for each species, leading to the growth of small sporophytic plants 0.4-0.8 in (1-2 cm) in size, the result of sexual reproduction.

The second phase consists of the growth of the juvenile individuals; at the end of the summer the frames are taken to the sea where the plants grow into sporophytes 6-8 in (15-20 cm) long in 1-2 months. The third phase is the development of the sporophytes; at the beginning of autumn the juveniles produced are transplanted on to cultivation ropes 98-328 ft (30-100 m) long, by simply plaiting them; the ropes are anchored to maintain them at a depth of 3-10 ft (1-3 m), forming farms: the plants can be harvested in 5-7 months. These species were initially cultivated in inland waters (bays, estuaries), but floating farms have spread out to colonize spaces on the high seas.

The cultivation of algae and cyanobacteria

The cultivation of algae and cyanobacteria requires a conceptually different approach from that of the future planning of seaweed cultivation as a source of food. "Sweetmeats" and "sponge cakes" of Spirulina platensis, a cyanobacteria that grows in tropical lakes, have long been eaten by local people in Mexico and Chad.

These organisms' high protein, vitamin, and mineral content led to their growing use as a supplementary food source to combat malnutrition in developing countries. Yet the industry's greatest growth took place in the 1970s due to interest in Spirulina as a dietetic food and a source of certain biochemical compounds. As a result, since 1970 many different continuous cultivation systems have developed commercially, based on artificial structures (pools, lakes) and modified coastal area near large lakes and maritime zones. These experiments took place in the United States, Mexico, Japan, Thailand, and Taiwan, and total production is now 1,000 tons a year.

Cultivated agars and carrageenans

After the Second World War, the diversification and growing use of phycocolloids led to increasing demand for them as raw materials, leading to overexploitation of some resources and shortages in the supply of others. Special culture systems had to be developed in the 1970s for the production of these raw materials. The cultivation techniques developed were mainly for red seaweeds producing agar and carrageenan, sectors based on the natural resources showing the greatest instability. The most important characteristic of all these cultivation techniques was making use of the high capacity for vegetative reproduction shown by some red algae. This made it possible to cultivate floating seaweeds--detached from the substrate-and also to use pieces of thallus as "seeds" to inoculate substrates (nets, ropes) or cultivation tanks.

The most important example of this type of cultivation is that of the carrageenproducing seaweed Eucheuma, developed technically in Hawaii and on a commercial scale in the Philippines. The low-tech cultivation system is very simple and this has led to its spread, reaching high production levels and stabilizing the sector's supply of raw materials. The method is to tie pieces (3.5 oz [100 g]) of the species under cultivation to the knots of the net, about 108 sq. ft (10 sq. m) above the bottom, or on polythene ropes that rest on the substrate, in places where environmental conditions will provide optimal growth. When the plants reach a weight of 2.6-3.3 lb (1,2001,500 g)--after approximately 90 days--, they are pruned and the process continues. An alternative to vegetative propagation was the use of artificial structures (channels, tanks) where the seaweed fragments float; in this case the system's higher technology and investment requirements led to the failure of the only large-scale experiment of this type ion a western country, cultivation of Chondrus in Canada. However, this type of cultivation is used in China and Taiwan for Gracilar-ia, an agar-producing species.

2.2 Reedbeds and marshland cultivation

Salt water is incompatible with most vascular plants, but some can tolerate the brackish water present in abundance in deltas and marshes. In brackish waters reed, reedmace, and bulrush beds form stands that can be exploited and where some crops may be cultivated.

Harvesting without planting

The use of helophytic vegetation (rushes, reeds, and bulrushes) forms part of a vast and varied culture going back millennia to the development of the first fibers and materials used by humans to make tools and utensils. This is poetically symbolized in a Babylonian legend for the origin of the world, which states "All the countries were seas; Marduk, the Creator, put rush mats on the waters, which he covered with mud."

Often considered useless weeds, these plants of noncultivated land have generally been a raw material available to anyone wishing to collect it. Its use is closely linked to the culture of self-sufficiency found in rural and less-developed societies, which makes optimal use of materials from their immediate environment to create objects with a wide range of uses (basketmaking, construction, furniture). In spite of the differences between the materials and methods used, or cultural ones, the usage of these materials shows some common characteristics in different cultures and civilizations.

Reeds and reedbeds

This group includes several species of grasses that form reedbeds on the shores of wetlands and all have long, hard, smooth, hollow stems. The most representative plants of this group and the most widely used in various parts of the world are the reeds (Arundo donax and Phragmites australis [= P.communis]), and bamboo (several species of Bambusa and Dendrocalamus). More than 150,000 tons of these raw materials are collected every year from wild populations, and some are now endangered. This has led to the first repopulations in countries like the Philippines and Thailand, which seek to develop them as a sustainable crop.

The stems are prepared for later use by cutting them, preferably at the time of leaf fall. After drying in a protected site to prevent the development of fungus, the stems are peeled by removing the remains of the dry leaves and leaf sheaths. They are then cut into longitudinal strips to obtain straight, flexible strips that can be folded and woven.

Canes and reeds are used to make baskets for agricultural and fishing purposes in villages in the littoral zone. In the Mediterranean and south Atlantic coasts of the Iberian peninsula, many examples of this tradition can be found. The canastras made from cane are used in the ports of the Algarve for carrying fish from the boats to the quay. Combined with other plant fibers (osier, juniper, and esparto) the various kinds of basket (cesto, canasta) are diverse expressions of the basket-making culture of the Mediterranean, for example in Ibiza. Because of the toughness and rigidity of this material, the method of weaving the canes is based on simple techniques that allow little variation in shape. On the other hand, their lightness and stability are two of the most important characteristics of this type of basket.

The use of cane and reed in popular crafts is an activity to which there are many references. The canizo, or hurdle, which consists of a framework of interwoven strips of cane or whole canes joined together, is the basic prefabricated unit typical of the villages of the Mediterranean basin and a basic element of partitions, coverings, palisades, and fences. The barraca, a construction typical of the albuferas (lagoons) and huertas (irrigated cultivated areas) of this region, are built with these canes that, when covered with mud, act as a support to obtain the necessary consistency and thickness. Bunches of rushes form the outer layer of the roofs. A similar form of construction is traditionally practiced in Iraq and other countries in the Middle East in the building of arches, combining the canes with baked mud. However, the type of popular construction that is most common in the littoral marshy zones in the south of Iraq are houses in which the cane is the only material used. Whole villages in this region are true reflections of a culture that achieves the maximum use of the natural resources of the local environment, based on a method of creation, maintenance, and transmission across the generations. In a like manner, in the whole of southeast Asia bamboo is widely used in the making of building elements for the construction of typical dwellings (beams, pillars, columns, laths, and grills). Other uses of these materials, more related to the aquatic environment itself, are the making of traditional fishing rods and the construction of different kinds of boats; the latter use of cane and bamboo, as well as many other vegetable fibers (papyrus, rushes), is very common in many peoples and civilizations. The fishers of the north coast of Peru and of Lake Titicaca use today, in the same way as they did in the times of the Inca civilization, caballitos de totora, little boats of totora (Schoenoplectus riparius) with a curved and barrowed prow. Likewise in the waters of China and Taiwan, different kinds of boats made of bamboo have been used for transport for thousands of years.

Rushes and cat tails

This name is given to a wide range of herbaceous plants with straight and flexible stems, characteristic of wet habitats, belonging to three families: Juncaceae, Cyperaceae, and Typhaceae. Their use, as with canes, goes beyond the littoral and neighboring environment and extends into the mainland, forming part of a common plant culture. The greater flexibility of these plant materials, compared with canes, allows the use of a very wide range of weaving techniques to make different fabrics and utensils, mainly for fishing nets and for the seats of chairs. These plants are generally collected in the summer and, in the case of bulrushes, when they are about to seed. The subsequent treatment includes careful drying until after a few days the fibers change to a straw color.

Rush matting, or more accurately woven rushes, are an example of the weaving practiced in the many coastal communities where this raw material grows: Juncus maritimus in Spain and Morocco; Cyperus tegetiformis in China; C. pangorei in India; and Scirpus lacustris in Portugal. Screens, roofing, insulation, baskets, and, above all, floor coverings for rooms are the main uses.

These vegetable carpets, used throughout Europe before the use of other fabrics, look beautiful and are warm in winter and cool in summer. Weaving fishing gear is a specialized form of rush weaving, although it was developed by sailors who had to stay on land, rather than by basketmakers. Creels are traps woven with plant stems in a variety of forms, to catch a particular species of fish or crustacean.

Bulrushes (Typha) and similar plants (club-rushes, reeds) are the main raw material for weaving the seats of chairs. The use of this type of resource in England (Scirpus lacustris) goes back to the 17th century and is still practised. In Catalonia and Valencia, in the Mediterranean coast of the Iberian Peninsula, it is still customary to make the seats of chairs with the local bulrushes--especially bulrushes from the Ebro delta--to make ordinary seats, and the great pond sedge (Carex riparia) is woven around the cores of the rush cording of better quality seats to give the seat a more pleasant color and feel.

Beach and marsh cultivation

Beaches and marshes appear unsuitable for agriculture. Yet in precisely these environments two of the world's most important crops--coconuts and rice--give their highest yields.

Coconut plantations

The coconut palm (Cocos nucifera) is a member of the palm family that grows spontaneously (or is naturalized) on the tropical beaches throughout much of the world, mainly on the coasts of the Pacific and Indian oceans (see 2.2.2. of this section). Its origin is still debated, but the fact that its center of variability is in southeast Asia means its center of origin is probably not far away.

Classical Indian works, such as the Mahabharata, the Ramayana, the Markhandeya Purana and the Brahmana Purana, all mention the coconut palm. The same name (nyiu or niu) is used, with small variations, from Malaysia to Hawaii, throughout Polynesia, and in Madagascar. This, together with archeological and ethnological data, suggests that the expansion of coconut cultivation was associated with that of the Polynesian peoples.

Today it is one of the world's most important tropical crops, mainly in southern Asia and Oceania, with a total area of about 8.6 million acres (3.5 million hectares), making it the world's most important tree crop. Its main product is its versatile fruit, and its other parts have so many uses that it plays a very important role in the cultures of many island or coastal peoples in the tropics.

Coconut cultivation does not require special care, except in plantations of delicate varieties or in extreme conditions. The coconut begins to fruit after six years and can continue until it reaches 80. The thick ovoid fruit is green on the outside until it ripens, when it turns yellowish. The edible part, usually referred to as the coconut, is in reality the stone of the drupaceous fruit, which has a very resistant fibrous covering. While the fruit is still green, it contains a sugary liquid that is widely drunk in the tropics. The coconut milk is gradually absorbed by the fruit as it ripens, but there is always some left, and it is a good substitute for water in emergencies on islands, desert coasts, and during very long sea voyages.

The coconut's most important commercial product is copra, the dried "flesh," or kernel, of the fruit. The coconut oil pressed from copra is used to make soap, cosmetics, margarine, and even lubricants. The fresh fruit is also an important foodstuff. The ripe coconut's fibrous husk (coconut fiber) is used to make rigging, matting, and brushes.

Coconut cables, as ancient Polynesian navigators were well aware, are elastic and buoyant and were highly valued until the introduction of artificial fibers. The palm's trunk provides wood for building and long fibers that are traditionally used to make nets and other fishing tackle, while the leaves are used for roofing. Like the trunks, they are used as fuel when dry. The sap extracted from the inflorescence is a sugar-rich liquid that can be drunk directly or fermented to make palm wine.

The world's leading coconut producer is Indonesia, with a harvest of 11.5 million tons, almost a third of annual world production, followed by the Philippines (8.6 million tons), India (4.6 million tons), and then Sri Lanka, Malaysia, Papua New Guinea, and Mexico, all producing about a million tons a year. The world's largest exporter of copra and coconut oil is the Philippines, followed by Indonesia, Malaysia, India, and Papua New Guinea. Although many Pacific states export only small quantities of copra, it is one of their main exports and one of the pillars of their economy. Coconut fiber is mainly exported by India and Sri Lanka.

Rice paddies

Rice (Oryza sativa) is a different, cultivated resource closely associated with coastal wetlands (coastal plains, deltas, and marshes). This cereal is consumed throughout the world, forming part of the diet of two-thirds of humanity, and is the staple foodstuff for more than half the world's population (about 54%) as a source of carbohydrates (93% by weight). The cultivation of most varieties of rice requires high temperatures and abundant water, mainly limiting it to the world's warm, wet regions, or temperate zones with long hot summers (such as Japan and the Mediterranean basin). Furthermore, the most common cultivat ion methods (controlled flooding of the paddies) favor the expansion of rice cultivation on coastal plains, marshes, and alluvial plains. Yet there are rice paddies high in the mountains, flooded or not, in many places in southeast Asia (see the section "The grain of abundance" in section 3.2 of volume 3).

Rice was apparently first domesticated in southern India, and is now one of the main crops in southern Asia. It first spread to southeast Asia (China and Indochina) and from there to the Philippines, Indonesia (2000-1500 B.C.) and then Japan (100 B.C.), encouraging the occupation of the large coastal plains and the delta areas. It was known in Europe (320 B.C.) and northern Africa (110 B.C.), but the initial spread of rice cultivation towards the west was interrupted in Iran, Babylon, and Syria (400-300 B.C.). Only the spread of Islam led to its introduction into several African cultures and in some countries on the shores of the Mediterranean. Much later, it was taken to the Americas by Europeans. Its importance in Madagascar is doubtless due to the Insulindian origin of the population of eastern Madagascar.

Many European marshes have been converted into rice paddies not so much due to need but rather to the fact that the site was ideal for its cultivation. Often the flooding of fields washes the soil of the salts it contains as a result of its closeness to the sea, thus making agricultural zones out of otherwise unsuitable areas. In any case, for centuries this wetland crop had a very bad reputation (or was even forbidden) in Europe because it meant maintaining considerable populations in areas exposed to malaria. The fields are in fact dry in winter, but from the spring to the autumn they are flooded, like any other wetland.

After the Second World War, rice cultivation once more thrived in the United States, South America (Brazil, Chile, and Argentina), and in southern Europe (Spain), because of increasing mechanization. Many southern Asian regions can produce two or even three rice crops a year, but different cultivation systems and high mechanization mean that the highest yields are not in these countries but in a Mediterranean country like Spain (6.3 t/ha compared with 4.2 t/ha in China).

In Spain, rice has traditionally been cultivated in Valencia (the albufera or lagoon of Valencia, the marshes of Castellon), and in the Emporda, but has increased greatly in the Ebro delta and the district of Andalusia called Las Marismas del Guadalquivir (Guadalquivir Marshes) to such an extent that production from these two areas is overtaking that of the Valencian rice fields, and the surplus is exported to the Far East and Latin America.

3. The use of animal resources

3.1 Hunting

Deltas, lagoons, and coastal wetlands offering abundant resources in the form of game, fish, bird eggs, and seafood were probably the first regions that humans exploited in coastal systems. This is clearly shown by the presence of oyster and other bivalve shells in ancient archeological remains (middens) in temperate (see chapter 4.2 of the section "Oceans and seas" in this volume) as well as tropical zones. Evidence has been found from 8,500 years ago of the exploitation of the mangrove swamps along the coast of Ecuador for collecting bivalves (Anadara tuberculosa) and for hunting peccaries, deer, and other animals. Nowadays, other forms of exploiting animal resources are carried out in these areas, such as aquaculture, animal grazing, apiculture, and ecological tourism, in addition to these traditional practices as old as the human settlements themselves. The most characteristic food-related activity has, however, always been the catching of aquatic birds.

Hunting for food

Subsistence hunting for meat affects a great number of mammals (deer, pigs, tapirs, etc.), birds, and reptiles (tortoises, lizards, iguanas, etc.). In many communities, gathering and hunting wild animals is as important to social and cultural activities as it is in terms of diet and nutrition. This is true, for example, of the Cree Indians from Quebec, who consume 267 lb (121 kg) of fish and game per person per year. Coastal communities (around Hudson and James Bay) primarily hunt migrating water birds such as ducks, geese (Branta), and divers (Gavia). The ducks and geese these communities capture represent 29-44% of the total consumption of fish and meat they have caught themselves.

The intrinsic characteristics and high productivity of coastal wetlands make them excellent places for water birds, particularly ducks, coots, and waders. Some species such as the flamingo (still hunted in some areas) and herons, which would be unthinkable to eat today, are depicted in medieval and Renaissance hunting scenes. The grey heron (Ardea cinerea), a fish-eating species, had to be completely skinned in order to get rid of its strong fishy taste. Nevertheless, ducks and geese have always been the most-prized species in coastal areas in Europe and the rest of the world.

Almost as many wildfowl are shot every year in Europe as in North America (11 and 17 million respectively), but Europe's bird stocks are much lower: 25 million ducks and geese in Europe as opposed to 100 million in North America. Thus, mortality due to hunting is 17% for the North American wildfowl population, compared with 44% in Europe, almost at the biological limit these species can tolerate. Wildfowling, aside from decreasing animal populations, also has other side effects. One of the worst is lead-poisoning caused by the ingestion of lead shot. This affects geese, ducks, waders and wetland raptors such as the marsh harrier (Circus aeruginosus) and the bald eagle (Haliaeetus leucocephalus). In 1990 alone, European hunters scattered an estimated 18,000 tons of lead shotgun pellets around the countryside, in a wide range of habitats--not just coastal areas, although a large percentage is used there. Hunting involves large sums of money and in Canada in 1982, for example, wildfowling and the hunting of other birds generated $180 million in direct profits and $513 million in indirect profits (in U.S. dollars).

In developed nations most hunting is a sporting activity rather than a response to the need to eat. Big game hunting aims for the biggest trophies and there is often an element of danger involved. This is the case with the Bengal tiger in the Indian mangrove swamps, certain deer species such as the fallow deer (Dama dama) in Europe, and the pampas deer (Ozotoceros bezoarticus) in Argentina and Uruguay.

Skins, furs, and feathers

Many mammals such as the musk-rat (Ondatra zibethicus), the raccoon (Procyon lotor), the mink (Mustela vison), and the coypu or nutria (Myocastor coypus), native to both the northern and southern hemispheres, live in coastal wetlands and are hunted by man for their furs.

The sirenians are also heavily exploited, such as dugongs (Dugong) and manatees (Trichechus), herbivorous aquatic mammals typical of river mouths, coastal lagoons, and shallow coastlines. Besides their meat, they are hunted for their very thick skins (2 cm), which are used for manufacturing, among other things, transmission belts for heavy machinery, dog collars, and belts. A close relative, Steller's sea cow (Hydrodamalis stelleri [=H. gigas]), native to the waters around Kamchatka, was hunted to extinction by Russian sailors and furriers in 1768. Other sirenians are very endangered because they are still hunted.

Crocodiles, caimans, and alligators are also much hunted for their skins. Many species such as the Mayan crocodile (Crocodylus moreletti) have been hunted to the brink of extinction, and there are many cases of large-scale poaching, even in theoretically protected areas. For example, in Honduras in 1988, 15,000 Mayan crocodile hides were illegally extracted from the Rio Platano Biosphere Reserve.

Marine animals, mainly mammals and to a lesser extent birds, have always been hunted for their oils, fur, skins and, to a lesser extent, for their flesh. Often they have been slaughtered on the beaches and islands where they rest and, in particular, those where they breed. A good example of this is the capture of penguins for their oil in their rookeries during the breeding season in Argentinean Patagonia, and another example is the near-extermination of the southern elephant seal (Mirounga leonina) during the 19th century. Sea lions (Otariidae) have traditionally been the most exploited group. The demand for pelts has decimated species and populations of some genera such as the fur seals (Arctocephalus) in New Zealand, southern Australia, and the Juan Fernandez Islands in Chile. For example, at the end of the last century over 70,000 South African fur seal (A. pusillus) pelts were sent annually to London, and populations plummeted. Hunting of Arctocephalus species continues, but at lower levels and under control. In Uruguay, it is easy to obtain legally-produced goods made out of the skin of the South American fur seal (A. australis), as 12,000 are captured annually on Isla de Lobos. Sea lions have also suffered particularly from commercial hunters, especially up to the 1950s. The plumage of water birds continues to possess commercial value, and they have long been used in many cultures for decoration and ornamentation, as well as for clothing. The best known case is the eider duck (Somateria), a large sea duck of the northern hemisphere; the female plucks the down (special soft feathers) from her breast to line the nest, and this down is used to fill the bedding quilts called eiderdowns, pillows, and anoraks (see volume 9, pages 102-105).

During the 19th century it was considered very fashionable for women to decorate their hats with bird feathers. Most came from egrets and herons, such as the great white heron (Egretta alba) and the snowy egret (Egretta thula). Their principal breeding colonies were in coastal wetlands, and because the most highly regarded feathers are part of their breeding plumage, it was necessary to capture these birds in their nests. Large-scale massacres took place and whole populations were annihilated. An estimated 5 million birds were slaughtered every year between 1860 and 1922. Over 2.5 million colonial-nesting birds were probably breeding in the Florida Everglades around 1870, but this population has been reduced to a mere 10%, mainly due to hunting. Other factors such as habitat loss and hydrological changes have also played a part. The outcry at the destruction of so many wild birds led to the establishment of the first bird protection groups, the Royal Society for the Protection of Birds (RSPB) in Great Britain and the Audubon Society in the United States.

The collection of eggs

The exploitation of marine turtles has some unusual aspects. Some marine turtles are caught in nets, but they are most frequently caught on the beaches where they go to lay their eggs. Various genera are involved, although the largest catches are of the green turtle (Chelonia mydas) and the hawksbill turtle (Eretmochelys imbricata), the latter being caught only for its shell, as its flesh is sometimes poisonous. Depending on the species, the shell, flesh (turtle soup), fins, and eggs may be used. Hunting is most intense in southeast Asia (Borneo, Philippines, Malacca Peninsula) and the Caribbean. In 1947, 706,960 turtle eggs, mainly from the green turtle, were collected on only three islands (now in the Turtle Isles National Park) in the Sulu Sea, Sabah (Malaysia). In 1975, also in the Sulu Sea, it was calculated that 5,000 adult turtles were being caught every year. The intense and abusive collection of eggs is largely responsible for the decline of these marine reptiles. Some species, such as the Kemp's ridley (Lepidochelys kempi), are gregarious in the egg-laying season and reach the beach to lay their eggs all at once, in what the Mexicans and South Americans call an arribada. In the 1930s, at least 40,000 females used to arrive on the beaches of Tamaulipas on the Gulf of Mexico to lay their eggs; due to the massive captures of turtles carried out in the 1940s and 1950s, barely 500 females now arrive.

Many seabirds, above all gulls and terns, breed in large colonies on low-lying coasts and beaches, and their eggs have long been eaten by islanders and sailors. The sooty tern (Sterna fuscata) is probably the most common and most widely distributed seabird in the tropics. Its colonies are huge, its population is very large, and its ability to lay replacement clutches means thousands and even millions of eggs can be taken every year without affecting the overall population. Egg collection is intense in all the world's oceans. For example, in the xelles Islands in the Indian Ocean, eggs still play an important part in the diets of the local population, who travel to more remote islands to collect them. Another example is Jamaica, where seabirds are exploited as food (mainly the eggs, but sometimes the chicks and adults), as a supposed aphrodisiac (the eggs), and as a fertilizer (their guano). In the 1920s, between 400,000 and 600,000 seabird eggs a year were collected, whereas in 1985 only 22,000 were taken, producing net profits of $2,000 U.S. dollars.

3.2 Fishing and shellfish gathering

Much of the world's annual fish catch--70-80 million tons--is caught on the continental shelf or in coastal zones. Coastal areas play a vital role because 50-70% of the commercial catch of marine organisms corresponds to species living in coastal waters or estuaries (it would be more accurate to say organisms that live in various kinds of coastal habitat such as lagoons, estuaries, mangrove swamps, or marshes at some point in their life cycle).

These commercial fisheries mainly catch species showing seasonal movements that tend to lay their eggs in the open sea, and their postlarval stages and juvenile forms then colonize estuaries, using these environments' surplus production to grow to the adult or pre-adult form. At this point physiological mechanisms come into operation that stimulate them to return to the open sea, where they reproduce and complete their life cycle. Fish and invertebrate densities vary considerably from one place to another in estuaries, partly because of the environmental gradient between salt and fresh water and partly because of the organisms' physiology and the features of their life cycles. Nevertheless, in general terms production in estuaries is very high--their biomass is as much as 6.8-11.5 times greater than in nearby marine environments.

The exploitation of rocky coasts

Rocky and wave-beaten shores are more difficult to exploit, but shellfish collectors gather there the intertidal benthic fauna. Many species are sought after: goose barnacles (Pollicipes) along the Galician or Colombian coasts, giant acorn barnacles (Mega-balanus psittacus) in Chile, mussels (Mytilus, Choromytilus, Aulaconya, Perna) in seas throughout the world, (Pyura chilensis) in Chile, sea-urchins (Paracentrotus lividus) in the Mediterranean, Strongylocentrotus doebachiensis in Europe and the North American Atlantic, S. franciscanus in California, Cidaris tribuloides and Diadema setosum in southeast Asia, to name but a few. On sandy ocean bottoms, holothurians (sea cucumbers) are also exploited (Stichopus regalis in the western Mediterranean, S. japonicus, Microthele nobilis, Thelenota ananas, Metriatyla scabra in China and Japan). Coral is also commercially exploited (discussed in the insert "Jewels from the sea").

The exploitation of deltas and estuaries

People have been collecting food from delta areas for a long time. In the case of the Mediterranean these include bivalve mollusks such as clams (Tapes), cockles (Cardium), and tellins (Donax); crustaceans such as prawn crayfish (Penaeus kerathurus), prawns (Palaemon), and the common shore crab (Carcinus mediterraneus); and of course a large number of fish. The largest catches in these areas include eels (Anguilla anguilla), sea bass (Dicentrarchus), giltheads (Sparus aurata), mullets (Mugil cephalus, Chelon labrosus), square-tail mullet (Liza), garfish (Belone belone), smelts (Atherina), soles (Solea), and flounders (Plat-ichthys). Most species are captured as adults although, as an exception, juvenile as well as adult eels are caught. As an example, the total fish catches in the lagoons of the Ebro delta oscillate between a maximum of 377 lb (171 kg) per hectare/year in 1965 and a minimum in 1987 of 163 lb (74 kg) per hectare/year (1 hectare=2.5 acres). In general, fisheries are declining in European deltas and estuaries due to many environmental problems, including reservoirs on large rivers, water pollution, the transformation of deltas, estuaries and coastal lagoons, urbanization, and the over-exploitation of natural resources.

The most important North American estuary fauna is its fish, although there are also abundant bivalves, cephalopods, and crustaceans. The most important species include powerful swimmers or surface-dwelling species, such as bluefish (Pomatomus), scads (Caranx), several species of clupeids (Brevoortia, Alosa), mullets (Mugil), various species of the salmon family (Salmo, Oncorhynchus), centropomids (Centropomus), sea bass (Morone), as well as the occasional megaloponid, such as the tarpon (Megalops atlantica). None of these species is sedentary; they only spend part of their lives in and around estuaries. There is a second group of species more closely linked to the ocean bottoms. These benthic species include the croakers (sciaenids of the genera Micropogon, Pogonias and Sciaenops), American sea trout (serranids of the genus Cynoscion), some atherinids (Menidia), osmerids such as the North-American smelt (Osmerus mordax), snappers (Lutjanidae of the genus Lutjanus), sturgeons (Acipenser), batrachoidids such as the toadfish (Opsanus tau), and various flatfish, principally belonging to the genera Paralichthys, Scophthalmus, and Pseudopleuronectes, such as the winter flounder (P. americanus).

The estuary environments of the North Atlantic are very important for both commercial and recreational fishing. In 1981, within the United States North Atlantic 3 mi (5 km) limit, commercial fish catches reached 1.6 million tons and recreational catches were 0.4 million tons. This contrasts with the catch for the 3-200 mi (5-322 km) zone where 1.1 and 0.3 million tons respectively were captured. Within Chesapeake Bay, the most important species by weight, though not by value, are fish: the menhaden (Brevoortia tyrannus), the pleuronectid (Paralichthys dentatus), the sea trout (Cynoscion regalis), and the bluefish (Pomatomus saltator), among others. Invertebrates command higher prices. In 1979 the collection of American oysters (Crassostrea sapidus), northern quahogs (Mercenaria mercenaria), soft-shelled clams (Mya arenaria), and other species produced profits of $87 million. In the Mississippi delta, 208 species of fish have been identified and some, but not all, use inland marshes and lagoons as breeding grounds. Some of the most abundant fish include Brevoortia patronus, Micropogonias undulatus, Anchoa mitchilli, Cynoscion arenarius, and Arius felis.

In southern Brazil, the enormous Lagoa dos Patos 5,405 sq. mi (14,000 sq. km) lagoon complex supports almost 10,000 local fishermen. The average fishing yield 1974-1982 was 403 lb (183 kg) per hectare/year (1 hectare=2.5 acres). The main species caught are the corvina (Micropogonias furnieri), the rosado (Netuma barba), the tainha (Mugil), the peixerei (Odonthestes bonariensis), the savelha (Brevoortia pectinata), and the camarao rosa (Penaeus paulensis).

In 1979, off the temperate coasts of Western Australia, 66% of the commercial fish catch (4870 tons) was made up of species that spend part of their life cycle in estuaries, and 15-20% were caught in the estuaries themselves. The largest commercial catches were of mullets, such as the striped mullet (Mugil cephalus) and Aldrichetta forsteri; sillaginids, such as the southern whiting (Sillaginodes punctatus and Sillago schomburgkii); and a bothid--a left-eye flounder--(Pseudorhombus jenynsii).

The exploitation of tropical lagoons and mangrove swamps

Tropical coastal lagoons, like those of other latitudes, are characterized by their high productivity: in tropical America fish production ranges from 40-7,000 lb (18-3,178 kg) per ha/year, with an average of 449 lb (204 kg) per ha/year. Very similar values are attained in other regions of the world: in southeast Asia, the range is 115-5,507 lb (52-2,500 kg) per ha/year, while in the Sabanilla and Luisa lagoons in Cuba, the range is 485-608 lb (220-276 kg) per ha/year. As in the case of marine fisheries, the most exploited species are those at lower levels of the food web, such as oysters (Crassostrea) and prawn crayfish (Penaeus). The cultivation of these species in America and Asia is opening up new ways to exploit these coastal environments, although not without the risk of conservation-related problems.

The structural and ecological characteristics of mangrove swamps provide ideal breeding grounds for many species. The waters are rich in aquatic life, and there are large catches of many fish, prawn crayfish (Penaeus), oysters (Crassostrea), and others. The mangrove swamps of the Gulf of Mexico are used by many juvenile fish for protection and as feeding grounds: Anchoa mitchilli and Arius felis (a brackish or seawater catfish), Bairdiella chrysoura, the spotted American sea trout (Cynoscion nebulosos), and Archosargus rhomboidalis, amongst others. However, adults of other species also visit the mangrove swamps to feed. This is the case of some snappers such as Lutjanus griseus, and toadfish such as Opsanus beta and Spheroides testudineus.

3.3 Stock-raising and aquaculture

Alongside purely extractive activities such as hunting and fishing, there are other ways of exploiting coastal fauna that require the input of nutrients and specialized skills: stock-raising in marshes and aquaculture.

Mariculture

The cultivation of bivalves, especially oysters and mussels, has been practiced for centuries in several countries. The Romans cultivated oysters in the Adriatic during the first century B.C. and in Japan the tradition seems to go back even further, though the earliest records date from the 17th century. The cultivation of the common or flat oyster (Ostrea edulis) began in 1858 in artificial banks on the Atlantic coast of France. The technique was introduced into Holland in 1872 with excellent results; the 500,000 oysters produced per year before 1870 in the Oosterschelde estuary leapt to 30 million per year once the artificial banks were in full production. Later on, the Portuguese oyster (Crassostrea angulata) was also introduced. In other countries such as the United States and Australia, production techniques were introduced by immigrants, although native species of oyster were employed. These were O. lurida and C. gigas (the Japanese oyster) on the American Pacific coast, C. virginica on the Atlantic coast, and C. commercialis in Australia. Harvests of 500-1000 million oysters have been achieved in Long Island Sound. Mussels (Mytilus edulis) are mainly cultivated on the Atlantic coasts of Europe, above all in the Galician Rias (100,000 tons per year) and the Wadden Sea (80,000 tons per year). The first attempts at mussel cultivation in Spain took place in the port of Tarragona at the beginning of the 20th century, and it was introducted into Galicia in 1946.

With regard to fish, aquaculture is a traditional activity in the warm waters of the Pacific and Indian Oceans that has become especially developed in Japan in the twentieth century. The practice extended to northern Europe in the 1960s (principally flatfish in Scotland and salmon in Norway) and the Mediterranean (gilthead [Sparus aurata] and sea bass [Dicentrarchus labrax]), and in recent years has reached tropical zones throughout the world. Some countries, such as the Philippines, Indonesia, and Taiwan, have transformed areas of mangrove swamps for the production of fish such as Chanos chanos. It has been calculated that by 1981 the Philippines was producing 10% of the fish it consumed from 240,000 ha (1 hectare=2.5 acres) of converted mangrove swamp. Organic and inorganic fertilizers keep productivity in fish farms very high, at 220-2,203 lb (100-1000 kg) per ha/year, with an average of around 1,322 lb (600 kg) per ha/year. In 1973 in Indonesia, the 190,000 ha devoted to fish-farming produced 53,000 tons of fish. Other species produced in mangrove areas include various species of mullet (Mugil) and the tilapia (Tilapia mossambica). In Singapore in 1972, carp production (Cyprinus carpio) ranged from 1,300-2,423 lb (590-1,100 kg) per fish pool.

Stock-raising in marshes

Temperate flooded pastures and coastal wetlands are often used as grazing, mainly for herds of cows and horses. Cordgrass (Spartina patens) pastures have been used in New England for livestock since colonial times. The passing of time and human selection has resulted in the development of breeds of animals well adapted to life in marshes, such as the horses of the Camargue in the Rhone delta and the black bulls of the Guadalquivir delta.

In the tropics and subtropics there are well-adapted bovines, such as the zebu (Bos taurus indicus), which feeds on floating vegetation or along riverbanks in flooded coastal and inland areas. The same areas also have many water buffaloes (Bubalus), originally from south Asia and with many different species in the Indian subcontinent, Celebes, Borneo, and the Philippines, with the most widespread and the most frequently used as a domesticated animal being the Indian water buffalo (Bubalus bubalis).

Mangrove swamps, especially in India, provide pasture for millions of domesticated ruminants such as cows, goats, and even camels. Overgrazing has affected many mangrove swamps and today numerous mangrove areas have been reduced to narrow, discontinuous strips with horizontal structures and appearances more reminiscent of an open woodland formation than a typical closed, mangrove forest. This degradation is especially noticeable in the arid regions of Kathiwara in the state of Gujarat in the northwest of the Indian peninsula. Forage is so scarce that herds of cattle reared for milk production feed in the mangrove swamps, especially on the fruits and leaves of the black mangroves Avicennia marina and A. alba. In this region and in some areas of southern Pakistan, domesticated camels depend on the mangrove for food; the sight of camels in the midst of a flooded marsh clashes with the typical image of the camel as a desert creature. The use of mangrove swamps for pasture is also common in the Ivory Coast, Oman, and locally important in the north of Australia (water buffaloes), Indonesia (sheepfolds), Benin, New Zealand, Japan, and Saudi Arabia.

Mangrove swamps are also widely used for apiculture in the Indian subcontinent, in particular in Bangladesh and in the Indian state of West Bengal, as well as locally in Australia and the United States.

3.4 Zoological tourism

The simple pleasure obtained from the observation of wild animals is a new nondestructive use of these resources. In recent years zoological tourism has become increasingly popular. Places such as the Everglades (Florida, U.S.A.), Donana (Andalusia, Spain), the Camargue (Provence, France), and the Nile delta (Egypt) are becoming increasingly popular tourist destinations. Perhaps the best example of this type of exploitation is the Galapagos Islands, where the almost 60,000 tourists per year, attracted almost exclusively by the wildlife, leave $80 million (in U.S. dollars) in the coffers of the Ecuadorian government. In many coastal areas, tourists are attracted, among other reasons, by animal communities, large terrestrial or marine animal species, and by fish. Throw in an exotic touch or two and round it off with submarine excursions, and you have a very attractive vacation destination. These types of destinations are centered on rocky and coral coasts, although some are in mangrove areas (the Caribbean) and coastal lagoons. An estimated two million people visited the corals of the Australian Great Barrier Reef in 1979 and spent around $100 million (in U.S. dollars).

The social and economic implications of this zoological tourism are worth mentioning. In 1981 in Canada alone, specialized trips for birdwatchers concentrating on water birds attracted 2.2 million Canadians, while a further 2.4 million went on trips in search of pigeons, birds of prey, and other species. The direct economic benefits reached $964 million. Experts in tourism believe that world ecotourism will grow by 20-25% every year during the 1990s and will mean greater visitor pressure on natural parks and other areas in need of adequate protection.

Mad about birds

Historically, British birdwatchers were the first zoological tourists. In Great Britain and other Anglo-Saxon countries a breed of person has emerged who collects observations of rare birds, meticulously checking off each new species as it is seen. Some enthusiasts have even formed clubs whose aim is to fill in the gaps in the bird lists of their members. If a rare bird turns up (normally in coastal areas), those members of the club who "need" it for their lists are contacted by telephone, and in no time an excursion is organized to go and see the new species. In England over 3,000 people have been mobilized at the weekend to go and see a particularly rare species.

Coastal areas attract zoological tourists because, due to their high productivity, large animal populations, especially birds, are found there. Some of the animals head for coastal areas to winter, some to breed, and others to molt. The Elbe Estuary in northwest Germany is the molting ground of the shelduck (Tadorna tadorna) and is also a favorite place for birdwatchers. Other birds are also present in large numbers, using the area to breed or just to feed. Breeding areas are one of the great attractions for the zoological tourist and 40,000 people a year visit the Punta Tombo Reserve in Chubut Province in Argentina to see the breeding colonies of Magallen jackass penguin (Spheniscus magellanicus). Other seabird species are equally attractive and breeding colonies of pelicans (Pelecanus), cormorants (Phalacrocorax), flamingoes (Phoenicopteridae), terns (Sternidae), gulls (Laridae), herons, and egrets (Ardeidae) also received human visitors. Nevertheless, in many areas these visits often have to be controlled to prevent disturbing nesting birds.

On the other hand, wintering and migration areas where large flocks of ducks, geese, coots, flamingoes, herons, waders, and other water birds congregate receive even more visitors. The most outstanding places for the observation of these birds are the coastal areas of the Netherlands, Great Britain, reserves such as the Everglades National Park in southwest Florida (which receives approximately 600,000 visitors annually), and the Camargue Natural Park in the Rhone delta on the French Mediterranean coast (which receives over a million visitors, mostly but not exclusively attracted by the fauna). Smaller but equally well-organized and perhaps more accessible reserves have very high densities of visitors. In Catalonia, almost half a million people visit the Ebro Delta Reserve annually, and the 1,409 acres (570 ha) of the Emporda Marshes Natural Park receives 40,000 a year, as many ecotourists as visited all the parks and reserves in Costa Rica in 1986.

Watching larger animals

The other great attraction for zoological tourism is the larger fauna. Sometimes, terrestrial species are the attraction, such as the Bengal tiger (Panthera tigris) in its natural habitat of the mangrove swamps of Sundarbans on the Indian-Bangladeshi border. However, aquatic animals, whether they live in the sea or in fresh or brackish water, seem to have even more appeal.

This is clearly shown by the sirenians, as well as the crocodiles and turtles. The green turtle (Chelonia mydas), for example, is the main tourist attraction of the Tortuguero National Park in Costa Rica. Colonies of marine mammals are also points of attraction, and are observed from dry land and from boats. In the Galapagos Islands, the most photographed animals are the island's 50,000 California sea lions (Zalophus californianus wollebacki). Watching whales and other cetaceans is a prized objective of growing numbers of ecotourists. In 1992, an estimated 60,000 people sailed from Golfo Nuevo on the Valdes Peninsula (Chubut Province) in Argentina to see the Southern right whale (Eubalaena australis). Andenes on the Island of Andoy on the northern coast of Norway had 28,000 visitors, more than the Tikal National Park in Guatemala, which contains the remains of the most spectacular Mayan city. A survey of the world's nondestructive whalewatching trips counted 303 established routes in 205 different localities in 19 countries. Most are strictly marine, although some routes are to observatories on the coast, as in Cape Town, or in coastal lagoons such as in Baja California (Mexico), where there are 12 different established routes in nine localities to watch the grey whale (Eschrichtius robustus) (see also the insert "From Captain Ahab to Commander Cousteau").

4. Management conflicts and environmental problems

4.1 Human pressure and pollution

In terms of problems concerned with environmental management, coastal areas are second to none. Whenever the subject is raised, westerners automatically think of the problems derived from human pressure on natural systems and contamination, legitimate concerns that originate from real problems. However, it is often forgotten that we are living with another, more serious tragedy: living conditions in human coastal settlements, especially in Asian countries.

Excessive demographic concentration

Human population density in coastal areas is very high. Moreover, delta areas are prone to suffer catastrophes such as floods, spring tides, and cyclones, as well as epidemics.

Since records have been kept, no generation of Dutch people has escaped the effects of a serious flood. The last such incident and the most serious to date occurred in 1953: 1,835 people and over 200,000 head of cattle died, 72,000 people were evacuated, and 200,000 ha (1 hectare=2.47 acres) of agricultural land and 47,000 buildings were affected. In the Jiangsu plains floods are also endemic. The Yellow, Yangtze, Huai, and other large rivers of the area have formed a huge flood plain with a very gentle slope. Their courses are now above the level of the surrounding land and over 1,864 mi (3,000 km) of river have been canalized and protected by earth banks up to 49 ft (15 m) high. This means that rain surges are particularly destructive. In 1931 and 1954, approximately 34,749 [mi.sup.2] (90,000 [km.sup.2]) were flooded (an area about the size of Austria). In the Ganges and Brahmaputra Delta, barely a year goes by in which there is not a serious high tide, causing thousands of deaths. The countless small islands exposed directly to the sea and the many small interior islands are most at risk when river freshets coincide with spring tides.

The vectors of many human diseases are aquatic organisms, at least at some stage of their life cycles. Mosquitos, fresh water snails, and worms are often present in the calm and productive waters of wetlands.

Many cultures have, as a result, considered these areas as unhealthy places to live, hence the term miasmas (the word malaria itself comes from the Italian words mal' aria, or bad air). Almost all of these diseases are discussed in more detail in other volumes of this series according to their importance in each biome: yellow fever, dengue, kala-azar and other hemorrhagic fevers, filariasis, and other tropical diseases transmitted by the digestive tract caused by drinking dirty water in volume 2; malaria in volumes 2 and 5; and cholera in volume 3.

The eutrophication of coastal waters

Supralittoral and littoral habitats are the marine environments most affected directly by humans. Any alteration to the coastline destroys natural coastal communities because very simple communities dominated by chlorophytes will develop on the new artificial surfaces, such as breakwaters and ports. These communities exhibit little fauna diversity, owing to the both drastic reduction in available food and the increase in inorganic particles in suspension that erode the substratum and hinder the organisms' settlement. Another common alteration is due to eutrophication processes. Large quantities of nitrates, phosphates, and other organic products are poured into the sea as a consequence of industrial and agricultural activity. This creates favorable conditions for a few opportunistic species that monopolize almost all of the accessible substrate. The dense seaweed belts along coasts, formed by the genera Ulva and Enteromorpha, are good indicators of recent eutrophication processes.

The loss of the mangrove swamps

Current climatic changes, particularly global warming, are causing the level of the sea to rise by almost 0.06 in (1.5 mm) per year. Mangrove swamps respond to these changes by opportunist colonization of the new structures created by this phenomenon, by using sheltered areas, or by advancing into areas being modified by the entry of sea water. However, the result is that mangroves are disappearing and are being reduced to a few steep coastal areas. Changes in sea level will produce even greater fragmentation in the areas occupied by mangrove swamps than already exists. During the Holocene period sea levels changed; the sea rose for 10,000 years at a rate of up to 4 in (100 mm) per year and did not begin to subside until 3,000-5,000 years ago. These phenomena obliged the mangroves to emigrate to where they are found today.

Human activities are causing alterations that are seriously affecting mangrove swamps. For example, the modification of watercourses (e.g., their diversion and canalization) deprives the mangrove swamp of its input of freshwater and nutrients from dry land and leads to reduction of the quantity of food available, which affects growth and causes an increase in salinity. In dry climates, the effects can be very severe and can cause high mortality. New roads and other building projects can also change drainage patterns and produce enclosed areas where the water cannot flow; nutrient supplies are cut, water levels rise, and the respiratory lenticels and pneumatophores are covered, thereby affecting gas exchange. This causes very high mortality, both in areas of heavy rainfall and in drier areas that receive water from other zones with greater rainfall. Changes in the extent of sedimentation also cause high mortality; mangroves are adapted to life in areas that receive a lot of sediments, but cannot survive sudden, massive accumulation of sediments caused by human activities such as construction or river diversion. A few individual trees will survive accumulations of sediments of 8-12 in (20-30 cm); all perish when sediment levels exceed 12 in (30 cm).

Mangrove swamps have been very damaged by contamination. Increases in water temperatures have very negative effects: temperatures over 950F (350C) cause high mortality and a loss of the species growing on the trees' roots. Temperatures over 1130F (450C) affect the trees themselves: they begin to produce small, chlorotic leaves, lose part of their foliage, and eventually die. These emissions of hot waters are produced by power stations and other industrial activities.

Mangrove swamps are also highly susceptible to oil spills; the trees die because their gaseous exchange organs (lenticels and pneumatophores) are blocked, and because of the petroleum's intrinsic toxicity. The tree's first response is to shed all or part of its leaves, and in dry climates this can cause soil temperatures and salinity to rise. Recently, a petroleum spill in Puerto Rico provoked a 59% loss in biomass in the mangrove canopy within 43 days, and a loss of 90% after 85 days. Toxic residues induce leaf malformation, reducing their photosynthetic surface, as well as affecting the roots and microbial activity in the substrate. The seedlings that take root in these conditions show malformations and reduced viability. Another important factor to take into account is that these mangrove soils cannot break petroleum down. It can be aerobically degraded by some bacteria, but the process is very slow in anaerobic mangrove swamps. Mangrove crustaceans bury themselves deep in the sediment and inadvertently help residues to penetrate further, and so they take many years before they are degraded.

Some contaminated waters (sewage, agricultural run-off), if diluted, can have a positive affect on the mangroves by increasing the amount of nutrients available, thereby stimulating growth. These waters also carry all sorts of residues, often originating far from coastal areas and including agricultural herbicides and pesticides that damage the mangrove flora and fauna.

Other activities that seriously affect mangrove swamps by changing the original habitat and eliminating existing natural populations include tourist complexes (including marinas and golf courses), saltworks, and above all, aquaculture installations for the cultivation of crustaceans and other marine animals.

The many different types of aquaculture are now common in many coastal areas and have recently boomed, especially in the tropics. Extensive areas of mangrove swamps have been transformed into artificial lakes; most of their flora and fauna is destroyed when the drainage channels and lagoons are dug. In 1977 in the Indo-Pacific region, three million acres (1.2 million ha) of mangrove swamp were destroyed to make way for aquaculture installations. Ecuador has converted 103,783 acres (42,000 ha) of mangroves to cultivate prawn crayfish (Penaeus). The success of the project (9913,084 lb [450-1400 kg] per ha/year) has aroused great interest in countries in South America (Venezuela), Central America (Costa Rica and Honduras), and the Caribbean (Trinidad and Tobago). The problem with these changes, apart from the damage they may cause to the ecosystem, is the irreversible loss of the mangrove forest, which in the short term will decrease the number of fry and post-larval stages of the very species being cultivated, such as prawn crayfish.

Because of their high productivity, mangrove forests are important sources of wood, timber, bark, charcoal, and other resources. If they are properly exploited with adequate techniques that take into account the particular characteristics of the species and their environments, as well as their potential for regeneration, then the mangroves can represent not only a subsistence resource but a resource of economic importance, as has happened in southeast Asia in the last 80 years.

4.2 Wetland drainage and silting up: the case of the Netherlands

Over the last few centuries, many low-lying and delta areas have been destroyed by drainage or silting up, as a response to the need for more arable land and to eliminate the diseases associated with wetlands, such as malaria. Nevertheless, this process has gone so far that it is time to reconsider such policies if we want to preserve what remains of our natural heritage. In some cases, the land reclamation has been truly spectacular and has transformed the whole face of a country. This is the case of the Netherlands.

The Netherlands are the most impressive example of how to make good use of a delta. A large part of the country occupies the combined deltas of four rivers (the Rhine, Meuse, Schelde, and Ems) and a considerable part of the country (60%) is below sea level. One part of the country is below sea level owing to an irreversible sinking of the land, the combined effect of construction of dykes, a rise in sea level, and land subsidence (8 in [20 cm] per century in total) caused by the drainage of wetlands and peat bogs. The other parts of the country below sea level are in this situation because of the desiccation of lakes caused by peat extraction for fuel.

The oldest evidence of human settlement in the area was found in 1976 in Hazedonk, near Molenars-graaf, in the province of Southern Holland. Remains discovered on a dune (once an island in the joint delta of the Rhine and Meuse) were determined to be 5,400 years old, indicating that the people of the Netherlands have coexisted for many years with the land and water of the shared estuaries of the Rhine, Meuse, and Schelde. Since the 12th century, the construction of dykes has been organized more systematically. The 29 mi (46 km) long Schlachte dyke in Freisland dates from the 11th and 12th centuries, and the western Freisland dyke dates from the 12th and 14th centuries. Some arms of the sea, penetrating far inland and potential threats to populated areas, were closed by dykes (dams), such as the estuary of the Rotte (Rotterdam) and the Amstel (Amsterdam). From the 16th century, the introduction of windmills to pump water from flooded areas made possible the drainage of lagoons and the creation of polders on a larger scale. Even so, the overall results were not entirely positive. Between the 16th century and the beginning of the 20th century, 2,124 mi2 (5,500 km2) were drained, but during the same time 1,931 mi2 (5,000 km2) were flooded by rises in sea level and land subsidence.

The 20th century saw the undertaking of two major projects: the Zuiderzee Project (1919-1975) and the Deltaplan (1954-1987). During this century, approximately 1,776 mi2 (4,600 km2) has been created in the Netherlands from land and from water. Overall, these projects have had a considerable impact. Only a few remnants are left of the original landscape of dunes, fresh and brackish wetlands, low-lying peat bogs, and riverside vegetation; they have all been replaced by polders and saltmarshes. Conditioning the landscape seems to have become the Netherlands' national pastime.

The Zuiderzee Project

From the 11th century onwards, the Almere, a region of saltmarshes and peat bogs separated from the sea by a dune cordon with a lake (Lake Almere or Flevo) in the middle, was gradually invaded by the sea and transformed into the Zuiderzee, a shallow bay occupying a large part of the northern Netherlands. This change was not only due to natural causes, but also to human activities (peat extraction, subsidence due to the drying out of the subsoil, etc.) favoring erosion by the sea. The overall objective of the Zuiderzee Project was to drain a large part of the 1,931 mi2 (5,000 km2) under water.

The first dyke was begun in 1919. The area was divided up into a number of sectors, each sector following a series of phases with slightly different objectives. The Wieringmeer polder was finished in 1930; the Afsluitdijk dyke, enclosing 1,448 mi2 (3,750 km2) of the Zuiderzee and creating the Ijsselmeer lake, was completed in 1932; the Noord-Oost and Zwarte Water polders were closed off in 1942; the Oostelijk Flevoland and Veluwerandmeren polders in 1957; the Westelijk Flevoland in 1968; and the last, Markermeer, in 1975.

The dividing up of the zone dramatically modified the area's former ecological characteristics; the tidal estuaries with their fresh to salt water gradients, the intertidal areas, and the brackish wetlands contrast enormously with the polders and their freshwater lagoons. This was not the Project's aim; it was only a public works project intended to increase the amount of land available for agriculture and for the use of the inhabitants of an overcrowded country. Phenomena such as eutrophication, the toxicity of microcontaminants, and the pollution of lakes and river beds were not understood when the plan was launched and were not taken into account at the time. Nevertheless, the philosophy underlying the creation and use of land reclaimed from the sea gradually changed during the course of the Project. Initially, the emphasis was on creating new arable land, as was the case with the Wieringermeer polder, the first to be drained. By the time the Noord-Oost Polder began, urban development plans were included from the beginning. Later on other considerations, such as their leisure, landscape, and natural functions, were taken into account (Flevo Polder). Although ecological considerations played no part in the original planning and development of the polders, some studies were undertaken to evaluate the biological changes taking place. Eventually, ecological considerations began to influence the construction and management of the new compartments. Finally, in the 1950s, the possibility of creating new wetlands like those that used to form part of the Dutch landscape was made moot. Thus, the Oostvaarderplassen was abandoned and left as a natural area. Reassessment of the Markermeer project led to the decision not to continue in the short term (when a new polder was being planned for the space the lake now occupies). For the first time, the value of a freshwater system had been recognized and integrated into the planning process as a positive feature rather than as a hindrance.

The Deltaplan Project

The Deltaplan was, just as the Zuiderzee Project had been at the end of the First World War, an enormous technical and economic venture designed to guarantee the security of the population and to safeguard the essential productive base of the country's economy. The main objectives were to reduce the length of the coastline from around 435 mi (700 km) to approximately 62 mi (100 km), protect the land from storms, and halt the increasing salinization. Secondary aims included opening the affected area to the exterior, creating infrastructures and facilities for market gardening, industry and leisure, reclaiming more land from the sea, and establishing drinking water reserves.

As in the Zuiderzee Project, the strategy was to divide the territory into compartments and then to work on each of them successively. In the Zuiderzee, this strategy had been motivated above all by the need to make the reclaimed sea floor suitable for agriculture. In the Deltaplan, however, the most important considerations were related to hydraulic engineering requirements. For example, the first dykes were constructed in places where the tidal movement of one estuary met that of another, taking advantage of the low flow rates in those places that would later be the site of emplacement of the dykes of Zandkreejdam, Grevelingedam, and Volkersakdam. Once this phase was completed, the larger external dykes were initiated, and towards the end of the project, work was started on the eastern sector of the Oosterschelde, although not before the actual details of the plan had been rethought and adapted. The final result consists of a compartmentalized area characterized by a large variety of different environments: freshwater lakes (Brielse Meer, Volkerakmeer, Hollands Diep / Haringvliet, Markiezaatmeer, and Zoommeer), saltwater and brackish lakes (Oostvoornsemeer, Veersemeer and Gravelingenmeer), and a sea inlet (Oosterschelde) with attenuated tidal movements (the tidal range near Yerseke is 10.7-12.1 ft [3.25-3.7 m]). Only two of the former estuaries, the Westerschelde and the Nieuwe Waterweg, are still open to the sea. However, an adjustable dyke to counteract storms is being constructed in the Nieuwe Waterweg. The area's division into compartments has brought some natural forces under control, and has made it possible to favor some types of environment (saline, brackish or freshwater), with a reduced tidal influence.

The Haringvliet Estuary

The Rhine and Meuse rivers' most important outlet to the sea, the Haringvliet Estuary, was closed by the construction of a series of dykes and sluices in 1970, thereby converting a brackish estuary with water movements in both directions, to the rhythm of the tides, into a permanent freshwater lake with much less water movement than before. This had an ecological impact and a new ecosystem began to develop. As had been foreseen, sediment deposition increased rapidly and will inevitably lead to drastic changes in the estuary's landscape during the remaining years of the 20th century and far into the 21st. As the level of the lake's bottom will continue to rise, presumably a new equilibrium will be reached and the river will meander through the sediments within the limits set by the two containing dykes on either side of the old estuary. Riverine vegetation will spring up on the sediments, and eventually the typical Dutch landscape of reeds and tree-lined rivers will be recreated, a process that it is planned to control. In the future, the Haringvliet sluices will not only act as an outlet to regulate the waters of the northern section of the Delta, but will also control this ongoing physical transformations. This is an interesting example of the controlled change of a given site, or to put it another way, an example of goal-oriented (or planned) ecosystem management, using a sluice as an instrument of ecotechnology.

However, the situation may actually be more complex. Pollution of the Rhine and Meuse rivers may have unforeseen consequences for both water quality and for the state of river beds and lake bottoms. Investigations carried out since the problem first became apparent in 1980 have shown that the sediments are contaminated by heavy metals, organic microcontaminants, and substances leading to eutrophication. Most of the contaminated sediments are concentrated in the Haringvliet and Hollands Diep area, and in zones of sediment deposition in the North Sea.

This revealed that the Netherlands were acting as a dump for all the chemical residues produced in the Rhine, Meuse, and Schelde basins. Over 100 [Mm.sup.3] of highly contaminated sediments had already accumulated. Over the next 20 years, 0.5-2.5 [Mm.sup.3] more contaminated mud will be deposited; this quantity will vary depending on the success of the Rhine Action Plan.

The most recent budget estimates for the program to clean the Delta, based on available technology, are 15,000-75,000 million guilders. A layer of contaminated sediments various meters deep covers the Delta floor in the eastern sector of Hollands Diep, while the layer over the rest of the zone is thinner. Polluting rivers in this manner is irrational: short-term profits measured in millions for industry leads to long-term (or not so long-term) losses to society measured in thousands of millions. The problem of the accumulation of toxic mud in areas of sedimentation near dykes and sluices is not confined to the Netherlands. The results are the same in any lake or estuary into which a polluted river flows, and the final result is always the same: river and lake beds all but devoid of life and unable to carry out the essential functions that this type of habitat should perform in any aquatic system. In the longer term, given that river and lake bottoms have become toxic storage systems, it is likely that even if pollution sources are eliminated, river and lake beds will continue to act as sources of pollution for decades. This raises many questions about the future impact of these accumulated layers of toxic sediment. Should they be left where they are? Should they be disposed of? If disposal is chosen, should they be removed immediately, or is it preferable to wait a certain period of time? What is to be done with the contaminated sediment?

The Grevelingenmeer experience

The Grevelingenmeer Estuary, a little to the south of the Haringvliet Estuary, was converted into a saltwater lake (17 g Cl-/ l) with outlets to the sea and the Oosterschelde when the Brouwer dyke was completed in 1971. After an environmental impact assessment the Dutch government decided to preserve it as a saltwater lake. The lake bottom is not contaminated, despite the existence of a number of diffuse sources of contamination. The lake's waters are always clear, even in summer (Secchi disc visibility = 33 ft [10 m]). Primary production rates are relatively high and are tending to grow, yet due to a fortunate combination of circumstances, eutrophication is not a problem. In the first place, unlike most aquatic ecosystems, here it is nitrogen and not phosphorus which limits growth. For this reason, high phosphate levels do not necessarily lead to eutrophication. On the other hand, large quantities of nitrogen gas are released from the system as a result of the denitrification occurring at the bottom of the lake. Bacterial denitrification is vital for the system, although it seems that the aquatic angiosperms (largely the eel-grass [Zostera marina] that now covers large areas of the now permanently submerged former intertidal zones) also play a very important role by secreting substances that may limit algal growth. Filter-feeders, such as the oysters (Ostrea edulis) and mussels (Mytilus edulis) that represent over 80% of the biomass of the benthos, may also be responsible for removing many algae.

The experience gained in Grevelingenmeer and from studies into the growth of aquatic angiosperms and their algal growth inhibitors, the possible control of algal blooms, and the role of filter-feeders in controlling them, are all being used to update water-management strategies in other parts of the Netherlands. In effect, the choice of creating a saltwater rather than a freshwater lake has broken with tradition, as the Dutch have always considered saltwater an agricultural problem. Nevertheless, the results obtained so far have led to the realization that any new environment has great potential if exploited in a positive way. It also led to recognition of the fact that the main aims in water administration can change with time.

The Oosterschelde: controlling an estuary

The Deltaplan originally proposed that the Oosterschelde would be completely closed off by 1978, then desalinized to create a freshwater lake. A large part of the water that was to fill the lake was to come from the Rhine and Meuse rivers. However, the Rhine's deteriorating water quality forced a review of the plan. As early as 1960 a new version was produced, still based on the choice between two alternatives: totally closing the Oosterschelde and desalinizing it, or leaving it open and reenforcing the dykes. This choice between two proposals, presented as "safety or the environment," met with popular rejection and led to the creation in 1973 of an commission of investigation. Its brief was to inform the Ministry of Public Works and Transport on all matters relating to safety and the environment of the works in the Oosterschelde, to study alternatives, to chose the most adequate solution from a point of view of both safety and the environment, and to advise the Ministry on possible alterations to the Deltaplan. The committee's investigations and deliberations led to them recommending the building of an adjustable breakwater to act as a storm barrier at the entrance to the Oosterschelde, which would leave 20% of the estuary on the seaward-side of the breakwater, and two additional dividing dykes. Thus, a normal tidal regime would be preserved in the western sector 39 [mi.sup.2] (100 [km.sup.2]), the central sector 116 [mi.sup.2] (300 [km.sup.2]) would have an attenuated tidal regime, while to the east of the dividing dykes a 39 [mi.sup.2] (100 [km.sup.2]) freshwater lake would be created. The commission's proposal was accepted by the government and passed by the Dutch parliament with a few amendments.

Total primary production in the Oosterschelde has been estimated at around 240 tons of carbon per day. Half of this is consumed by phytoplankton and benthonic filter-feeders, and the other half by respiratory processes. A small phytoplankton input from upstream adds 10 tons of carbon per day, although otherwise detritus flow is negligible. The average amount of net primary production of carbon is relatively low (250 g C/m2/year). The Oosterschelde is also an excellent area for rearing many different organisms and is economically important for the production and cleansing of mussels, oyster culture, harvesting of bivalves, and fishing for crustaceans, flatfish, eels, and anchovies.

The Oosterschelde is nature's handiwork as well as the result of human intervention. What is novel about it is that it is so huge and that the changes took place so quickly. The results allow us to understand how difficult were the problems that arose over the last few centuries. For example, in 1867 large changes occurred as a result of the construction of the Kreekrakdam, the dyke which communicates Zuid-Beveland with Northern Brabant. The influence of the Schelde River was eliminated and the Oosterschelde grew more saline, less susceptible to fluctuations in salinity, and free from the waters of today's highly contaminated Schelde. The Grevelingendam (1965), and later, the Volkerakdam (1970), increased the influence of the contaminated waters of the Rhine and Meuse, and marked a significant change in the Oosterschelde ecosystem.

On the other hand, the adjustable breakwater on the Oosterschelde, the siphonic sluices on the Grevelingendam, and the Philipsdam floodgates (that keep the freshwater of the Krammer-Volkerak sector from mixing with the saltwater of the Oosterschelde from the Maskgat) will enable the estuary to be controlled and allow a planned economy to be introduced into the southwest Netherlands.

The Deltaplan was concluded in 1987. The adjustable dyke against storms and the dividing dykes have split the Oosterschelde, as has already been said, into three zones: one tidal, one with little tidal movement, and the third a freshwater lake. The predicted impact of the compartmentalization is complex. Thirty-three percent of the intertidal areas and 63% of the brackish wetlands have been lost, while there has only been a net gain of 7% of areas of shallow water. As a consequence of the decrease in tidal movements, the remaining wetlands and intertidal areas are decreasing due to erosion. Every year, 0.6% of the wetlands and 0.3% of the intertidal zone is lost. Biomass production on intertidal surfaces will decrease, affecting the populations of crustaceans, fish, and birds. The maximum number of birds counted per day and the number of birds/day (the estimated average of birds an observer could see in a given area) will drop dramatically, with serious repercussions on the populations of waterbirds throughout western Europe. On the other hand, the area of hard substrate (dykes, protection against the flow, the concrete used to build the structures, etc.), an excellent base for sessile communities, has doubled in the area with reduced tides. Canals will become shallower. Detritus input will not vary appreciably. Water stratification and oxygen exhaustion will be infrequent and local in occurrence. The use of the dyke adjustable against storms and regulation by the Philipsdam floodgates are of great importance to the area's ecosystem.

It might be thought that these processes simply show nature at work. However, humans have also played an important part. The Oosterschelde is the fruit of the interaction of human technology and effort with the forces of nature. If the Kreekrakdam between northern Brabant and ZuidBeveland had not been built in the last century (1867), today the Oosterschelde would bear no ecological resemblance to a river estuary and would be merely another inlet of the sea. Furthermore, the area would be highly contaminated, like the Westerschelde. Without the Volkerdam and Philipsdam large amounts of contaminated materials from the Rhine would have been deposited in this area. These dykes also make it possible to control the flow of freshwater that previously existed in the region. The level of biodiversity is also due to human intervention; the introduction in certain areas of hard substrates, such as rocks in dykes and concrete pillars, has created suitable conditions for communities that live in rocky environments. The eastern part of the Oosterschelde, once a polder, is today a protected area with clear water whose temperature is moderated. This explains the appearance of species in this area not associated with these latitudes.

The lessons from this experience

The economic and technological energies invested in this century's great hydraulic engineering projects in the Netherlands cannot be automatically extrapolated to less economically and technologically developed parts of the world, but some general lessons can be applied to any delta zone.

Comparing today's complex dykes and floodgates with the primitive Dutch dykes of seaweed mixed with sand, or even with the simple dykes of compacted earth erected in many parts of the world, it might be thought that everything that was technologically possible has now been put into practice, and all that needs to be done is to transfer this technology. But we now know that making technological limitations the only restriction on human activity causes contamination, disturbances, and the destruction of available natural resources, including the human environment. Too much attention was paid to consumption and the under-exploitation of certain areas, and not enough to their correct use and exploitation. It was as if human beings did not form a part of natural systems, which is a great error. The dramatic evidence of the contamination of the Rhine's waters and bed, and those of other rivers, has served to warn humans that we cannot simply adapt the environment to our needs.

In landscapes molded by humans, the environment should be subject to conditions intended to ensure the development of a healthy ecological base. This century has seen most of the world's rivers and estuaries altered by human intervention. Dams and canals have been built for irrigation and navigation, rivers have been diverted, and dykes and floodgates have been built. All this has been done in a relatively short period of time to stimulate the economy, provide security of life and property, ease transport, increase energy production, and to supply water for domestic, agricultural, and industrial use. The ecological consequences of these actions have been enormous. Whole landscapes have been changed and have adopted new functions, sometimes with disastrous secondary effects for the humans who had exploited the resources of the river basins, their estuaries, and the nearby sea. When the Aswan Dam was built in Egypt, almost all the coastal fisheries failed--a high price to pay, and one that must be added to the direct economic costs of construction. Similar problems are arising in the Mississippi Delta, which could disappear in the 21th century.

Technologists, planners and managers have tended to ignore not only the implications of their projects that do not directly affect their primary objectives (for example, agricultural development in the Zuiderzee and security against catastrophic risks in the Deltaplan), but also the projects' direct and indirect effects on areas outside their immediate scope. They have not paid enough attention to the fact that, whatever their project's intention, some areas that are not directly transformed will nevertheless be profoundly altered by the changes involved. Landscapes may begin to function in a quite different way, which will have ecological, economic, and social consequences.

To sum up, in this century the application of new technologies has increased humanity's capacity to alter the normal ecological and social functioning of coastal waters. Unfortunately, technological capacity and basic social and economic needs, such as safety, mean that shortsighted decisions are often taken that may harm coastal ecosystems. The planning, execution, and operation of many projects takes a long time. It seems that for projects of the size of the Deltaplan, 20-40 years is typical. Yet each new generation has new ideas and new priorities. Society changes and must make new decisions and adopt new ways. One example is the political reconsideration that was involved in the Oosterschelde project and the final decision to construct an adjustable storm breakwater and two dividing dykes, instead of following the initial plan to completely close the estuary.

278 Human presence in coastal areas goes way back in time. Today it is difficult to find a delta, wetland, sea cliff, or beach without traces of human presence.

[Photo: Gemma Porta]

279 The Shatt al 'Arab, the scene of fierce combat in the 1980-88 Iran-Iraq war, flows through land created from the Persian Gulf by the alluvial deposits of the Tigris, Euphrates, and other rivers of the region.

[Photo: Lochon / Gamma]

280 The alluvial soils of southern China have seen agricultural development since ancient times, often linked with rice cultivation.

[Photo: P. Aventurier / Gamma]

281 The extent of human settlement in and around the Bay of Tokyo is evident from this false color photograph taken from a satellite using the MSS (multispectral scanning system). The blue shades reveal the built-up areas, which not only occupy the entire coastal plain, but have also completely changed its coastline.

[Photo: AGE Fotostock]

282 Birds, fish, and crustaceans are used as ornamental motifs in these cloths woven by the Cuna people, and illustrate the dominant themes in the lives of this mainly gathering community. The Cunas, a people who live on the Atlantic coast of Panama and on a series of small coastal islands, base their economy on fishing, although they also practice farming.

[Photo: Tony Morrison / South American Pictures]

283 Sediments washed down by the Yellow River in northern China. These fluvial sediments, along with the loess transported by the wind and then eroded by the river, have shaped a remarkable and very fertile landscape. They have given the waters of the river--the Yellow River (Huang in Chinese)--and the sea they will flow into--the Yellow Sea--their characteristic color.

[Photo: George Mobley / National Geographic Society]

284 Harvesting kelp (Ma-crocystis) on an industrial scale off California. Since the Second World War, the phycocolloid production industry has consumed greater and greater quantities of seaweeds, the reason for this hightech collection method.

[Photo: Francois Gohier / Ardea London Ltd.]

285 Bundles of chascon seaweed (Lessonia nigres-cens) in a market in Melinka in southern Chile. No other country has anything like Japan's tradition of cultivating seaweed for food, but in some areas of southern Chile it is not uncommon to find different species of seaweed for sale on vegetable stalls. In 1989, 62,723 tons of chascon were sold.

[Photo: Leo Collier / Planet Earth Pictures]

286 Roadside drying of rhodophytes on the island of Terceira (Azores). Anywhere flat and sunny will do for this simple operation, performed in thousands of places on the island. It is a modest economic activity that complements fishing.

[Photo: Ramon Folch / Ankh]

287 Petri dish with agar, on which bacterial colonies are developing. Agar, the standard culture medium in all laboratories, has no nutritional value but is an excellent support that is easy to handle and inoculate.

[Photo: Sinclair Stammers / Science Photo Library / AGE Fotostock]

288 The traditional use of seaweeds as a foodstuff in Japan has led to an important agricultural industry, as can be seen in this transport of recently collected phylloids of Laminaria at a specialized farm.

[Photo: Robert Jureit / Planet Earth Pictures]

289 Eucheuma cultivation on the African shores of the Indian Ocean. There is no cultural tradition of seaweed culture in Africa, but the demand for carrageenans has made large intertidal plains into productive areas since this crop was introduced. Production continues throughout the year, although the complete cycle from "planting" the seaweed to collection is only 3-4 weeks. Every day, during the 2-3 hours the tide is low enough, each operation (preparation, planting, and collection) must be performed as a different part of the exploitation of this plant.

[Photo: Bojan Brecelj / Still Pictures]

290 Marsh Arab selecting reeds and rushes. The "Marsh Arabs" of southern Iraq, like their Sumerian ancestors long ago, typically use rushes and bulrushes (Juncus, Schoenoplectus), reedmace (Typha), and reeds (Phragmites) to build houses and boats. The choice of the most appropriate material for each purpose is essential to successful construction.

[Photo: Jonathan Wright / Bruce Coleman Limited]

291 Fisherman preparing his tackle while sitting on the remains of Posidonia oceanica on Mallorca, with a puu bait of small crustaceans. Posidonia is used for other purposes, such as packing delicate objects (which is why it is called "glazier's grass" in Catalan), bedding for livestock, and fertilizer.

[Photo: Jaume Sureda]

292 A Menorcan fisherman weaving fishing creels. Many handmade fishing devices throughout the world are made by fishermen using the plants in their environment. At his feet is a fyke woven of rush (Juncus), and he is starting a new one combining sedge with strips of bulrush (Arundo).

[Photo: AGE Fotostock]

293 Broken coconuts being dried to obtain copra. Next to a group of coconut palms growing by the beach of the island of Taveuni (Fiji), workers remove the fibrous covering and break the coconut, exposing the pieces to sun to dry. Copra is the most important commercial coconut product.

[Photo: Jean-Paul Ferrero / Auscape International]

294 Coconuts germinating in a coconut (Cocos nuci-fera) plantation in the Philip-pines. The coconut is never completely buried, and the new palm's first roots and leaf emerge from perforations in the hard shell.

[Photo: Douglas Dickins / NHPA]

295 Threshing rice (Oryza sativa) by hand in the coastal fields of Bali (Indonesia). As well as these coastal rice paddies, the island is famous for its terraced rice paddies on mountain sides.

[Photo: Murray & Associates / Fototeca Stone]

296 Marsh hunting scenes are frequent in the Egyptian tombs of the 18th dynasty (1567-1320 B.C.). In this detail from the paintings in the tomb of Nebamun, a nobleman from the court of Thebes, the lifelike depiction of the animals contrasts with the stylized representations of the human figures. Surprisingly, the cat (which was sacred to the Egyptians) seems to be participating actively in the hunt.

[Photo: Ronald Sheridan / Ancient Art & Architecture Collection]

297 Dugongs (Dugong dugon) are still hunted on several islands in the Pacific. The photograph shows a group of hunters in their sailing canoe with outrigger in Papua New Guinea.

[Photo: D. Parer and E. Parer-Cook / Auscape International]

298 Sea turtle meat and egg stall on a market stall in Pointe Noire in the Congo. On the Atlantic coasts of Africa, as well as in other continents, the eggs and meat of sea turtles are highly valued and still hunted, despite a ban.

[Photo: Michel Gunther / Bios / Still Pictures]

299 The extraction of seabird excrement or gua-no for use as agricultural fertilizer is of great economic importance on the arid Peruvian coastline. The enormous fertility of Peruvian coastal waters and the resulting abundance of pelagic fish stocks leads to the presence of large colonies of seabirds. Their excrement has been accumulating for thousands of years on the sea cliffs where they nest and rest since there is almost no rain to wash it into the sea. The accessibility of the deposits to marine transport makes them easy to exploit. This coincidence of factors led to the phosphorus and nitrogen of the depths of the Pacific fertilizing the exhausted fields of 19th century Europe, once progresses in chemistry and plant physiology had unravelled the mysteries of nutrient cycles. The saltpeter (sodium nitrate, NaNO3) deposits in Tarapaca (Peru) and Anto-fagasta (Bolivia before the Pacific War [1879-1883], Chile afterwards) were used for the same purpose as the guano and, after all, originates from the same place. The famous Chile saltpeter, for decades the world's most important agricultural fertilizer, is extracted from ancient marine evaporitic basins. Saltpeter and guano still provide agriculture with phosphorus and nitrogen, despite having been somewhat displaced by the discovery of chemical fertilizers after the First World War.

[Photo: Thierry Petit / Bios / Still Pictures]

300 A shellfish gatherer in the Ebro Delta. Strapped to his equipment--a bagshaped net attached to a large rake--this shellfish gatherer walks through the breaking waves collecting tellins (Do-nax) and other bivalves that live buried in the sand.

[Photo: Xavier Ferrer]

301 Fishing in mangrove lagoons is normally carried out on a small scale with traditional implements. This group of women and children from Ambanizana (on the western coast of Madagascar) are in waters open to the Mozambique Channel, and are about to begin fishing with a reed basket. Their technique consists of frightening fish towards the carefully positioned basket by hitting the water with sticks, stones, or simply their hands.

[Photo: David R. Austen / AGE Fotostock]

302 Oyster cultivation is one of the most productive and traditional aquaculture activities in Europe and, in particular, in France. The picture shows oyster cultivators in the Thau lagoon on the Mediterranean. The German naturalist Karl Mobius (1825-1908) developed the concept of biocoenosis after studying oyster beds. In 1869 Mobius traveled to France to study the oyster cultivation techniques then being developed, in order to consider their possible introduction into the German section of the Wadden Sea. He arrived at the conclusion that the decline in the natural oyster banks in Schleswig-Holstein was an indirect consequence of overexploitation due to market expansion, caused by the growth of rail transport. He concluded that a species' abundance or rarity does not follow simply from its reproductive potential (which in the case of the oyster is enormous), and that it is necessary to take into account all the other species that live in the same environment, feeding there and competing for the same resources. Mobius named the set of organisms that lives in a particular place and of the environmental factors the biocoenosis. This concept was a forerunner of the idea of the ecosystem.

[Photo: AGE Fotostock]

303 There has been a marked increase in aquaculture activities in mangrove swamps in tropical countries since the 1960s. In the photograph, a worker on an Indonesian fish farm is hauling in a net full of fish from the pool where they have grown to a size suitable for sale.

[Photo: Mark Edwards / Still Pictures]

304 Coastal marshes provide excellent places for extensive cattle-raising. Even in recently protected wetlands without stock-raising traditions, such as the natural park of Aiguamolls de l'Em-porda (Catalonia), cattle have been successfully introduced. In the photograph we can see a group of horses next to a lagoon in this coastal area.

[Photo: Francesc Muntada]

305 Visiting natural marsh-es has become a mass recreation activity, at least in highly urbanized developed countries. As result many wetlands near densely populated areas and with good communications (at least at the edge), like these marshes in southern France shown in the photograph, receive many thousands of visitors every year.

[Photo: Josep Maria Barres]

306 Demographic pressure in Bangladesh forces hundreds of thousands of people to live permanently in areas under threat from cyclones, high tides, and floods. On April 29, 1991, all three phenomena coincided in the Ganges Estuary, causing the death of tens of thousands of people and cattle, and leaving many more without a roof over their heads. The photo shows a part of the Island of Hatia in the eastern sector of the mouth of the Ganges, one of the areas most affected by the 1991 cyclone and high tide. Ninety percent of homes were destroyed and over 10,000 people died (25,000--10% of the population--died in the catastrophic cyclone of 1970).

[Photo: Shahidul Alam / Drik Picture Library]

307 Oil spills from oil tanker accidents destroy coastal systems only too frequently. In 1967, the coast of Brittany was affected when the damaged Torrey Canyon spilled 50,000 tons of crude oil into the English Channel, and a few years later, the Amoco Cadiz also had a large spill. The photo shows a scene from the second oil spill to devastate the coasts of Brittany.

[Photo: Joaquim Reberte & Montserrat Guillamon]

308 Thousands of acres of mangrove swamps are destroyed annually for a great variety of reasons. In the photo, a fishing settlement in Malaysia has been built in a former section of mangrove swamp. Population growth in southeast Asia has led many people to look for new areas to exploit or to live in. Traditional as well as modern aquacultural techniques are well-suited to mangrove swamps.

[Photo: Ivan Polunin / NHPA]

309 The Wadden Sea and surrounding areas in a SAR (Synthetic Aperture Radar) image taken from the satellite ERS-1 in July 1991. From the top downwards, the photo shows the Friesian Islands (from left to right, Texel, Vlieland, Terschelling, and Ameland), the Wadden Sea, the Afsluit dyke, the Ijselmeer lake or inland sea, and the polders attached to solid ground.

[Photo: Courtesy of the Euro-pean Space Agency]

310 Floodgates on the Haringvliet dyke. These flood-gates relieve the pressure of the Rhine and Meuse floods, especially during freshets.

[Photo: Lisette Pons]

311 The Oosterschelde dyke system seen from the north. In the foreground, the Hamden dyke and adjustable sluices and the artificial island of Roggenplaat; in the middle distance, the Schaar von Roggenplaat dyke with adjustable sluice gates and the large, central, artificial island with its quays, landing jetties and barriers; in the background, the Roompot Channel adjustable dyke. On the left the choppier waters of the sea contrast with calm waters of the estuary on the right. The dykes with adjustable sluice gates permit the circulation of tidal waters in both directions when there is no risk of spring tide, or the estuary's complete closure if meteorological conditions make it necessary.

[Photo: Lisette Pons]

312 Some of the principal parameters in the tidal sector of the Oosterschelde. The columns show the values taken before the beginning of the project, those predicted during the project, and those measured or estimated in the final evaluation report (1991), as well as the percentage variation between the final and initial figures.

[Source: data provided by the author]

313 Everything in this harmonious scene in the Netherlands is the result of human action. The people of the Netherlands have separated land from sea, just as God did on the third day of the biblical creation. Then they built houses, and now they grow crops on land won from the sea and marshes. It is no exaggeration to say that the Dutch have created their own country.

[Photo: Adolf de Sostoa & Xavier Ferrer]
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Publication:Encyclopedia of the Biosphere
Geographic Code:1USA
Date:Oct 1, 2000
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