Printer Friendly

5 Protected areas and biosphere reserves in the littoral zone.

1. Protected coastal systems

1.1 The historical process of protection of coastal zones

Protection of wetlands and other coastal spaces was originally due to concern arising from the recognition of habitat destruction as one of the main causes of the increasing rarity, and in some cases extinction, of species. One of the oldest protected spaces in Europe is probably Farne Island off Northumberland in northern England, where protection of the flora appears to go back to the 7th century. Saint Cuthbert, Bishop of Lindisfarne retired there and ensured that local people respected his solitude and the wildlife, a tradition that has been generally respected for more than 1,200 years.

However, not all coastal spaces have been so lucky, nor have they been as technically well-managed as those in the Netherlands. Wetlands are disappearing everywhere, or being so significantly altered as to completely change their environmental character.

Normally, the causal agent is humankind, but the reasons for change are many and varied, both intentional and unintentional. Although some wetland loss is inevitable (and in some cases is even desirable), the scale of the losses is causing serious local and international concern. This has resulted in action for their protection at both national and international scales.

The protection of wetlands

In temperate areas, the most important criterion used to conserve wetlands has been their use by aquatic birds for overwintering or as resting points on migrations. For this reason, the Santa Lucia Lake and Estuary Reserve was createdin 1897 on the coast of Natal (South Africa, then a British colony) and also the reserve of Naardermeer, near Amsterdam, in the Netherlands, promoted in 1904 by a society (Vereniging tot Behoud ven Natuurmonumenten in Nederland) which grew out of a movement opposing the installation of a city garbage dump in this wetland, an important breeding site for the shoveler (Anas clypeata) and the purple heron (Ardea purpurea).

Birds are valuable indicators of environmental quality because of their ability to respond rapidly to environmental changes and their location at the higher levels of the food chains. They are also easy to observe. However, the national censuses of aquatic birds coordinated by the International Waterfowl Research Bureau (IWRB), do not cover all countries as thoroughly. In tropical environments where data on waterfowl are often scarce, other criteria are often used such as their value as egg-laying sites for marine turtles, the presence of mangrove swamps or coral reefs, or as habitats of scarce and endangered mammals, such as the manatee, which is the main object of conservation reserves in Guatemala and Indonesia. The names of the Sea Elephant Conservation Area (Australia), Polar Bear Pass (Canada), Turtle Beaches/Coral Reefs of Tongoland (South Africa) clearly explain the reason for their conservation.

Wetlands are subject to many differing pressures. In both developing and industrialized countries wetlands are often the sites of activities and practices that are not always compatible with the balance of nature or even with their continued existence. The widespread recognition and awareness of the value of wetlands, on which many populations depend for their livelihood, requires more imaginative measures to improve resource management to ensure the preservation of both species and habitats, and the efficient use of the resources available.

Planning for efficient use requires the study of not only the ecological processes that maintain the wetlands, but also their socio-economic situation, with a view to understanding the rural economy and how the use of resources is administered. This information makes it possible to adopt measures to improve resource management and also to improve their market value, and to diversify the rural economy to free it from unnecessary pressures. It is necessary to control activities and their impact in order to adapt them if conditions should change.

Projects of this type are being performed in many parts of the world, aiming both to preserve wildlife and to encourage agriculture, fishing, livestock raising, and hunting.

Much current investment in wetland conservation will help the rural population to develop long-term strategies for resource use. Only this kind of integrated planning will make it possible for many of the world's wetlands to survive in the future.

Protection of rocky coasts

Birds, in this case colonial sea birds, have also been historically the factor leading to the protection of rocky coastal habitats, although their number and area is smaller. As already mentioned, the remote precedent of Saint Cuthbert's devotion has partially protected the Farne islands. In 1909, the U.S. Bureau of Sport, Fisheries, and Wildlife declared part of the coast of the Bering Sea a refuge for migratory birds, as well as the Pribilof Islands in Alaska (which were also declared a game reserve to protect the seal populations). However, the spectacular nature of the coastal cliff landscape has also often played an important role. The Flinder's Chase reserve on Kangaroo Island, in Southern Australia and the Wilson's Promontory National Park, two of the continent's first protected spaces (1905) became parks because of their spectacular landscapes as well as their rich and unusual fauna.

There are now many protected spaces that include stretches of rocky coastline, but most are islands or the coast of much larger inland areas, whose main interest is not their coastline, and are thus discussed in the corresponding volumes of this work..

1.2 International cooperation

Perhaps more than any other habitat type, wetland conservation shows the need for international cooperation in the development and application of conservation action. Migratory species, such as waterfowl, use a series of wetlands in different countries, and often breed in one country and overwinter in another. The fish caught in the fisheries of one country may have spent their early life in the waters of another country. Not only species move from one wetland to another, but water is also a shared resource, as it runs through the wetland systems of different countries.

Growing awareness of the interrelationship between wetland systems has led to the development of a series of international initiatives that aim to support conservation action in more than one country. Bilateral and multilateral agreements have been drawn up concerning protection and use of particular water bodies (such as the Wadden Sea, shared between Germany, Denmark, and the Netherlands) and drainage systems.

Networks of natural parks have been set up by both governmental and nongovernmental agencies, with the explicit aim of protecting the migration routes of particular species, and a convention has been adopted on the international cooperation in the conservation of wetlands--the Convention on Wetlands of International Importance especially as Waterfowl Habitat, better known as the Ramsar Convention, after the Iranian town where it was signed in 1971.

The Ramsar Convention's definition of a wetland is any type of wetland habitat whether natural or artificial, permanent or temporary, with water that is flowing or static, fresh, brackish, or salt, including the marine waters up to 20 ft (6 m) deep at low tide. The Ramsar Convention was signed in 1971, but did not come into effect until December, 1975. About 100 countries had ratified it in 1998. The Convention has also set up a Wetland Conservation Fund that aims to provide developing countries with the means to improve wetland conservation and management.

The governments that have ratified the Convention incur four main obligations: (1) to designate at least one wetland area for inclusion on the List of Wetlands of International Importance; (2) to promote wise use of wetlands in its territory; (3) to consult each other about implementing obligations arising from the Convention, especially, but not exclusively, concerning shared wetlands or water systems; and (4) to create wetland reserves.

2. Coastal UNESCO MAB biosphere reserves

2.1 General considerations

One of the most important aims of the UNESCO Man and the Biosphere (MAB) Programme is to develop a network of biosphere reserves that is representative of the world's ecosystems. These include coastal systems, and so there are also biosphere reserves in coastal areas. In 1998 there were 315 reserves in more than 80 countries covering an area of about 200 million hectares (1 hectare=2.5 acres). About 80 of these (roughly 60 excluding islands) affected coastal areas. Almost a quarter of these (16) were in the United States. Other countries with a significant number of coastal reserves include the United Kingdom (10) and Australia (6). Examples include the Hawaii Islands National Park (United States), Sian Ka'an (Mexico), Banados del Este (Uruguay), Donana (Spain), the Wadden Sea (the Netherlands and Germany), the Kiunga Marine National Reserve (Kenya), Palawan Island (Philippines) and the Southwest National Park (Australia).

Natural values and conditioning factors

Coastal biosphere reserves are usually made up of both terrestrial and marine components. They often contain tidal channels, muddy and sandy tidal flats, coral reefs, coastal dunes, freshwater and salt marshes, flooded forests and upland dry forest environments. Some also include offshore islands. A good example of a coastal reserve is the Sian Ka'an Biosphere Reserve in Mexico, as 120,000 of the site's 528,000 hectares (1 hectare = 2.5 acres) are marine.

As these biosphere reserves include both marine and terrestrial environments, they generally show a high degree of biological diversity. As an example, the Sian Ka'an has 4,000 plant species, including 120 trees and shrubs, as well as 28 species of mammal, 350 bird species, and 52 fish species.

Another example is the salt marshes and areas between the marshes and the sand dunes in the Wadden Sea Biosphere Reserve in northwestern Europe; it has 100 species of halophilic plants, and between six and 12 million birds pass through it each year. In general, coastal biosphere reserves support large numbers of resident and migratory birds. As they are geographically isolated, endemics are very frequent: the Hawaii Islands Biosphere Reserve is an extreme case as 95% of its flowering plants are endemic to Hawaii. Coastal biosphere reserves have cultural, commercial, and subsistence value and the human component may be of great importance for their planning and management. Cultural heritage and artifacts are important features of many coastal biosphere reserves. As an example, the Hawaii Islands Biosphere Reserve is rich in remains of native villages, temples, graves, paved trails, shelter caves, agricultural areas, and archeological sites dating back centuries. Making use of resources is of benefit and value to local people. Clear examples include the hunting of wild pigs within the limits of the Hawaii Islands Biosphere Reserve, the extraction of foodstuffs and medicines from the Sian Ka'an Biosphere Reserve, the exploitation of the mangrove swamp in the Palawan Island Biosphere Reserve (Philippines), and the traditional culture of mussels and lugworms for fish practiced in the Wadden Sea Biosphere Reserve where sand is also extracted for building use. Finally, in many coastal biosphere reserves the commercial use of resources is very important. For example, in the Wadden Sea commercial fishing is of great economic importance. Many plaice, sole, and herring spend their earliest juvenile stages there. Tourism is also important in many reserves, especially activities such as sightseeing, camping, hiking, sailing and fishing. Hotels and other tourist attractions are often located within the support zone.

Management problems

Coastal biosphere reserves face many threats, one of the principal ones being pollution. In the Wadden Sea, for example, water quality is declining due to the discharge of sewage and the accumulation of heavy metals and pesticides. A second threat is the degradation and depletion of resources, whether due to overexploitation, or the impact on habitats of leisure activities and illegal hunting. There is the well-known example of overexploitation of aquatic animals for their fur in Banados del Este Biosphere Reserve in Uruguay. The conflict between different types of resource use is another threat facing these reserves, mainly due to the conflicts between shifting agriculture, ranching and forest exploitation. Habitat damage and destruction are a fourth threat to coastal systems: plantation development, drainage schemes (in the Donana Biosphere Reserve in Spain), human-provoked fires and natural threats such as cyclones (in the Sian Ka'an) are examples. These problems are compounded by the lack of technical, human, and financial resources. Further, the inaccessibility of many reserves has limited monitoring, research, conservation and administrative functions. Management of coastal reserves increases in difficulty when a number of national or regional governments are involved. Often, legislation protecting marine systems lags far behind terrestrial systems.

Coastal biosphere reserves, like terrestrial ones, consist of a core area serving a mainly conservation function, the protection of habitats and of endangered plants and animals. This central area is surrounded by a buffer and/or transition zones, in which controlled use of resources is permitted. The core zone of Sian Ka'an Biosphere Reserve in Mexico is about 280,00 hectares of the 528,000 hectares (1 hectare=2.5 acres) forming the reserve as a whole.

Management activities are often guided by the preparation of plans and programs that are sensitive to local conditions. Naturally, research also helps management activities. Studies of marine resource management and use are very important, as their results have to be applied to the local economy and also provide for the conservation of resources. This is the case of the studies of lobster ecology in the Sian Ka'an Reserve or those carried out on the effects of harvesting lugworms in the Wadden Sea.

2.2 Biosphere reserves affected relatively little by humans

Most biosphere reserves have been recognized as protected areas within the country they belong to and so they are often national parks or nature reserves as well as reserves. Their importance means that many are protected under forms of protection of international scope. They are almost all located in relatively unpopulated areas, with low or almost nonexistent population densities, not only in the reserve itself but also a large surrounding area.

The Sian Ka'an Biosphere Reserve

Mexico was one of the first countries to have sites included within the list of UNESCO-designated biosphere reserves. The Sian Ka'an Biosphere Reserve is on the Caribbean coast in the least developed zone of the Yucatan peninsula, and seeks to protect important ecosystems and also to help local communities to develop their use of renewable natural resources.

The Sian Ka'an Biosphere Reserve was established by Presidential Decree in 1986, in Quintana Roo, one of Mexico's most biologically rich states. It is the country's third largest protected area, occupying 528,000 hectare (1 hectare =2.5 acres) of the central coastal portion of the Yucatan peninsula. Sian Ka'an is a Mayan name, meaning "the beginning of the sky."

The reserve lies on a partially emerged coastal limestone plain, where terrestrial ecosystems merge with marine ones, forming a complex hydrological system with abundant lagoons, marshes, dunes, mangroves, and flooded as well as nonflooded forests on higher ground. The low-lying plain's water table is never more than 26 ft (8 m) below the surface, meaning that 75% of the terrestrial part of the reserve is flooded each year during the wet season. The soil and the underlying limestone are highly permeable, explaining the absence of surface streams and rivers.

On higher ground, the only water bodies are the sink holes called cenotes that are typical of the Florida and Yucatan peninsulas. One of the area's most important features are the coral reefs, part of the barrier reef system running along the Caribbean coast of Central America. In addition to their great beauty and the diverse marine life they support, these reefs play a physical role in protecting the coastline against storms and in providing a habitat for several species of commercially important crustaceans and fish, such as the young of the spiny lobster Panulirus argus, which depends on reefs for the growth of its larvae that mature in the bays and lagoons.

Characteristics and natural values

Sian Ka'an's climate is tropical, with warm summer rains and frequent cyclones. There are no meteorological stations within the biosphere reserve, but there are accurate data from other nearby ones. The mean monthly temperature range from 72[degrees]F (22[degrees]C) in January to 81[degrees]F (27[degrees]C) between May and October, but in winter the temperature may drop as low as 41[degrees]F (5[degrees]C). Annual rainfall is 43 in (1,100 mm), three quarters of which falls in the wet season between May and October, when strong easterly blow almost continuously, and cyclones, as well as more severe tornadoes (mangueras) ravage the coast.

Sian Ka'an combines Central American and Caribbean characteristics. Within the reserve nearly 4,000 species of plant have been found, including 520 vascular plants. Mexican scientists have described 12 different types of vegetation, including semi-evergreen, semideciduous and flood forest, tasital or palm savannah, fresh and saltwater marshes, and petenes or forest hummocks, mangroves, dunes, and keys.

The petenes, isolated forests only found on the Florida and Yucatan peninsulas, are of especial interest in the Sian Ka'an Biosphere Reserve, because this is where reach their greatest size and density. True islands of forest, with a diameter ranging from tens of meters to a kilometer or more, they emerge from the marshes and often have a sink hole in the center. On these relatively dry islands are vegetated by sedge (Cladium), reed (Phragmites australis), mangrove (Conocarpus erectus), several species of Bucida, Crescentia and Haemotoxylon. The trees are "chechen" (Metopium), figs (Ficus), Plumeria and palms of the genera Thrinax and Sabal that reach 39-49 ft (12-15 m) in height.

Medium altitude semi-evergreen forest occupies one fifth of the reserve and represents the climax in the nonflooded regions, although due to disturbances there is little mature vegetation in the accessible parts of the reserve. There are 120 species of trees and shrubs, the common canopy trees include sapodilla (Manilkara zapota), black chechen (Metopium brownei), incense tree (Bursera simaruba) and Lysiloma latisiliquum. The most abundant plant is "chit" (Thrinax radiata) a palm 26-32 ft (8-10 m) in height, and other common plants include laurels (Nectandra coriacea and N. salicifolia), manche (Byrsonima bucidaefolia), sea grapes (Coccoloba spp.) and Caesalpina gaumeri. The oldest, least disturbed parts of the forest typically have abundant climbers and epiphytes.

Semideciduous forests cover much less area than the semi-evergreen forest, occupying approximately one tenth of their area. About 100 species of trees and shrubs occur. Some of the most typical ones are incense tree (Bursera simaruba), Lysiloma latisiliquum, sapodilla (Manilkara zapota), black chechen (Metopium brownei), Piscidia piscipula and Psidium sartorianum. A further characteristic of these forests is the abundance of Beaucarnea ameliae and the cuca palm (Pseudophoenix sargentii).

Flood forest is found in the lower, wetter areas. Logwood (Haematoxylon campechianum), Bucida spinosa and cocobolo (Dalbergia glabra) form an open canopy. Tasiste (Acoelorrhaphe wrightii) and calabash tree (Crescentia cujete) are frequently found in more flooded areas. Beneath the canopy the vegetation is luxurious; epiphytes and light loving abound. Where black chechen (Metopium brownei), sapodilla (Manilkara zapota), Bucida buceras and Lysiloma latisiliquum are found, they form a closed canopy about 39 ft (12 m) high and understory plants are relatively scarce.

The tasitales, communities of tasiste (Acoelor-raphe wrightii), are scattered throughout the reserve. It is a tree that can form monospecific "islands," but is more often associated with other species, such as the mangrove fern (Acrostichum danaefolium), Bucida spinosa, Jamaican sedge (Cladium jamaicense), mangrove (Conocarpus erectus), cocobolo (Dalbergia glabra), icaco or coco plum (Chrysobalanus icaco) and the "chit" palm (Thrinax radiata). Grass communities cover large zones in the south and north of the reserve, among the mangrove swamps and the inland forests where salinity is not excessive. Grassland occurs as a mosaic of three intermingled associations, dominated by masiega (Cladium ja-maicense), black sedge (Schoenus nigricans) and eleocaris, (Eleocharis cellulosa) respectively.

There are extensive areas covered by dwarf mangrove swamp to the east of the freshwater marshes. The most important plants, mainly the 7 ft (2 m) red mangrove (Rhizophora mangle), cover 35-40% of the surface area. Soil salinity is high and during the dry season the ground completely dries, while during the wet season the surface is flooded by shallow water that may reach temperatures of 122[degrees]F (50[degrees]C). The main trees that tolerate the salinity of the peripheral mangrove swamps are the red mangrove (Rhizophora mangle), the black mangrove (Avicennia germinans) and white mangrove (Laguncularia racemosa), with an average height of 33 ft (10 m). Plants present in the drier areas include the button mangrove (Conocarpus erectus), sapodilla (Manilka-ra zapota), and "chit" palm (Thrinax radiata). Non-tree mangrove species include the mangrove fern (Acrostichum danaefolium) and the climber Rhabdadenia biflora.

The coastal dune zone is found in the part facing the open sea and stretches 40 mi (64 km) from the reserve's northern limit to Punta Allen and from Punta Hualastoc to Punta Tupac. Due to its proximity to the Antilles, the flora shows many affinities with the Caribbean flora, making it unique in Mexico. There is also a large endemic component, including the Caribbean laurel or geiger tree (Cordia sebestana), black chechen (Metopium brownei), tasiste (Acoelorraphe wrightii), sea rosemary (Suriana maritima), Turinar radiata and fisherman's tobacco (Tournefortia gnaphalodes). Several introduced species have been widely planted on the dunes, such as the coconut (Cocos nucifera), which has displaced the natural vegetation on about half the dunes, and the casuarina (Casuarina equisetifolia) and Colubrina asiatica.

The keys consist of coral, sand, and the remains of marine shells accumulated by the waves over hundreds of years. The only dominant species on the smaller dunes is the red mangrove (Rhizophora mangle). On the larger dunes there is also turtlegrass (Thalassia testudinum), the main food of marine turtles. Many of the drier zones have been disturbed. All the mammals of the Yucatan region are found in the reserve. There are 28 species of mammals, including five species of cat; the jaguar (Panthera onca), the puma (Felis concolor) the ocelot (Felis pardalis), the margay or tigrillo (F. wiedii) and the jaguarundi (F. yagouaroundi). The area also supports large populations of tapir (Tapirus bairdii), one of the most endangered species in the Central American fauna. Although the Caribbean manatee (Trichechus manatus) is endangered and is nearly extinct on the Yucatan peninsula, it finds refuge in the reserve's brackish lagoons, making it difficult to observe and to count its numbers. It breaks surface only to breathe or to browse the foliage of overhanging mangroves. The forests are the habitat of Geoffrey's spider monkey (Ateles geoffroyi) and the Guatemalan black howler monkey (Alouatta villosa). There are an estimated 350 species of bird in the reserve, two thirds of which breed inside the reserve. Due to the great diversity of aquatic habitats, marine birds are very well represented. There are also 16 species of raptor. The reserve is a very important breeding site for the magnificent frigatebird (Fregata magnificiens), cormorants (Phalacrocorax), the roseate spoonbill (Platalea [= Ajaia] ajaja), the greater flamingo (Phoenicopterus ruber) and jabiru (Jabiru mycteria). 42 species of amphibians and reptiles have been recorded. The beaches are used for nesting by the green turtle (Chelidonia mydas), and also by the endangered hawksbill turtle (Eretmochelys imbricata), loggerhead turtle (Caretta caretta), and leatherback turtle (Dermochelys coriacea). The endangered Morelet's crocodile (Crocodylus moreletti) and the American crocodile (C. acutus) live in the wetlands and mangrove swamps.

Management problems

800 Mayans live in the Sian Ka'an Biosphere Reserve, the descendants of a culture that has lived on the Yucatan peninsula for centuries, shown by the wealth of archeological remains found throughout the reserve. The Maya are mainly fishermen and agriculturalists, depending on the spiny lobster (Panulirus argus) as their main source of income, and they supplement their diet by subsistence maize cultivation and livestock raising. 23 Mayan sites have been found within the reserve, including a recently excavated artificial canal 15 mi (24 km) long. Tulum, one of Mexico's most visited archeological sites, is just to the north of the reserve and the ruins of Chunyaxche, Vigia del Lago and Xamach are located nearby. It is known that the Maya used about 200 plants. The Maya originally numbered about five million and spread into Guatemala and Belize. They formed the first urban societies in Latin America, the archeological remains of which can be seen in the Tikal reserve in Guatemala, as well as on the Yucatan peninsula. It is thought that these communities' overexploitation of natural resources, especially agricultural land, led to their downfall as the fertile soils eroded and became depleted.

Scientific research within the reserve focuses on obtaining basic knowledge of the area and then applying it to the management and conservation of its natural resources. Research is coordinated by the Centro de Investigaciones Quintana Roo (CIQRO), and extensive research has been carried out on different aspects of the reserve's flora, fauna, ecology, geology and hydrology. A team from the University of Mexico is currently evaluating marine resources. Visiting scientists can stay at the reserve.

The El Ramonal experimental plot, set up in 1986 by the Amigos de Sian Ka'an (Friends of Sian Ka'an Reserve) have served to develop agricultural techniques to preserve the delicate Yucatan soil, using intercropping and crop rotation. Studies are being performed to ensure sustainable exploitation of resources, such as the lobster and the "chit" palm (Thrinax radiata), integral components of the local economy. The botanists in the Amigos de Sian Ka'an working on the declining populations of the cuca palm (Pseudophoenix sargentii) are performing comparative studies of different populations to set up a management plan to ensure their survival. The programme assesses the palm's current status, its growth rate, determine the environmental influences on its growth, and identifies cultivation methods to reduce pressure on the wild populations. Once the study has finished, this information will be given to the local population through an extensive education program.

Sian Ka'an has been hailed as the most effective nature reserve in Mexico. It is also thought to be one of the best examples in Latin America of the integration of conservation and the needs of the local inhabitants. One factor contributing to its success has been political support at all levels of government, i.e. municipal, state and federal authorities. The decree creating the reserve makes provision for a council of representatives involving municipal, state and federal authorities as well as local fishermen, small property owners, coconut plantation owners and farmers. A comprehensive management plan has been prepared, in collaboration with the local population, that provides for the reserve's division into different zones for different management purposes. To achieve biosphere reserve objectives, the plan proposes seven programs covering administration, patrolling, natural resource management, public use, education and extension, research, and monitoring.

Tourism started to develop in the 1970s, when the beaches of Tulum, to the north of the reserve, started to attract foreign visitors. Tourist facilities spread south, in the form of trailer parks and rustic huts, despite the lack of basic services. In any case, the northern part of Quintana Roo has become the second most important tourist area in the country, and plans have been made for the urban development of the Cancun-Tulum tourist corridor, including Cozumel Island. In 1983, tourist use of the reserve was low, probably due to access difficulties, isolation and a lack of drinking water and electricity. In fact, within the reserve services are restricted to the coastal strip. In the north there is a small hotel, a fishing club, and three zones for trailers and cabins which can all be reached by road from Tulum. In the rest of the reserve there is a small hotel and cabin area in Punta Pajaros, only accessible by sea or air.

Sian Ka'an is not without challenges for its managers. Management is difficult due to the lack of access to much of the reserve. Cyclones make the construction of facilities difficult, and high humidity increases building costs and requires regular maintenance of equipment. Furthermore, economic resources only allow the employment of ten park rangers, too few to patrol such a large area. Reserve boundaries have not been clearly defined, due to the presence of peripheral ejidos or cooperatives, which complicates the management of the border zones.

The development of tourist installations to the north of the reserve is the chief concern. Uncontrolled urban growth along the coastline with sewage discharges directly into the sea, seriously threaten the life of the reefs. Fires in this area have also destroyed about 135,000 hectares (1 hectare = 2.5 acres). The forests have also been exploited to such an extent that many valuable species are becoming locally extinct. These include mahogany (Swietenia macrophylla), cedar (Cedrela odorata), aceituna (Quassia simarouba [=Simarouba glauca]), ziricote (Cordia dodecandra) and guacayan or lignum-vitae (Guaiacum sanctum). Soil erosion is increasing in the deforested areas. There is the potential for pollution from the ejidos (communal land held as cooperatives) Felipe Carrillo and Andres Quintana Roo as these towns are within the reserve's hydrographic basin. Domestic, industrial and agricultural waste can penetrate the calcareous soils and reach the subsoil aquifer.

The reserve is supported by the Amigos de Sian Ka'an a group channelling private sector funds to reserve management activities, in collaboration with the municipal, state and federal governments. In March 1989, an agricultural development program began that forms part of the Amigos de Sian Ka'an Regional Development Project. Nine families from Tres Reyes, a local Mayan community participated, and following the workshop, a community farm was formed set up with help from the association. The project is now offering an extension program to transfer agricultural technology to surrounding Mayan communities in order to produce a more effective system of traditional agriculture (milpa in Mayan lands). A public information project also promotes the reserve in several communication media. The Amigos de Sian Ka'an newsletter provides a regular up-date on the reserve's activities and leaflets inform local communities about the research results. As a direct result of local collaboration there have been several noteworthy achievements. The excessive commercial felling of forests has been largely controlled, and commercial hunting has been reduced. The people of the Chunyaxche area work as the reserve's staff and collaborate in captive breeding projects for wild fauna. However, the long-term conservation of the Sian Ka'an reserve depends not only on the reserve's resident population who have been effectively involved in reserve management through the projects, but also depends on the support of the communities outside its limits. The reserve is surrounded by the traditional ejidos or communal landholdings, that are now caught up in transition from traditional land use within the Biosphere Reserve and the increasing outside generated by the recent tourist boom. As the impact of these outside changes will depend to a large extent on the way in which these buffercommunities manage their natural resources, the Amigos de Sian Ka'an Regional Development Plan is beginning to address socioeconomic conditions outside the reserve.

The Banados del Este Biosphere Reserve

The Laguna Merin lies at the center of a vast complex of temperate coastal wetlands covering 1.2 million hectares (1 hectare=2.5 acres) spanning the border between Uruguay and Brazil. The southern or Uruguayan part of these wetlands is protected as the Banados del Este Biosphere Reserve, which comprises lagoons, wetlands, dunes and seasonally flooded land on the Atlantic coast.

The Banados del Este Biosphere Reserve, established in 1976, was one of the world's first internationally recognized biosphere reserves. Its 200,000 hectares (1 hectare=2.5 acres) include the Santa Teresa Historical Monument and National Park created in 1937, one of the first parks in South America. The Laguna Negra Reserve and the Laguna de Castillos y Palma Fauna and Flora Reserve to the south are permanent brackish lagoons with an average depth of 23 ft (7 m). The Dunas de Cabo Polonia Nature Monument was specifically set up to protect a nationally importance site for coastal dunes and their associated vegetation; it is a popular picnic area for Uruguayans. The Biosphere Reserve also includes the Cabo Polonia Forest Reserve and a series of Protected Sea Lion Islands. The lagoon complex has arisen as a result of the area's poor drainage. Coastal dunes form a physical barrier preventing rivers finding their way to the sea, causing them to form long meanders along the coast, forming large expanses of shallow water. The area receives 43 in (1,100 mm) annual rainfall, most of which falls in winter and rapidly runs off the hilly parts to the west, swelling rivers and flooding the land around the lagoons. Four large rivers, the Yaguaton, the Tacuari, the Olimar and the San Luis, flow through the reserve into Laguna Merin.

Characteristics and natural values

The acidic, peaty, soils have mineral-rich sediment deposits, which produce fertile soils. In the Banados de Santa Teresa, the streams drop their sediment loads leaving deposits several meters thick. Scattered among the Banados are what are called cerritos de indios (Indian hillocks), small artificial mounds 66-98 ft (20-30 m) in diameter and from 2-10 ft (0.5-3 m) high. Although their purpose is unclear, they appear to have been made by the region's pre-Colombian inhabitant's, who lived off the abundant swamp wildlife and perhaps by trading animal skins with neighboring populations.

The Banados del Este wetlands are extremely important in buffering downpours. They absorb the excess water that would otherwise run off and flood neighboring agricultural land. The regular floods fertilize the soils during the winter and produce abundant pasture for livestock. This was the main use of the region's land and in fact three quarters of the country's land is still dedicated to pasture. The flooding regime of Banados del Este, with its nitrogen-rich soil, make it ideal for rice cultivation. In summer, when the soils dry out, the lagoons act as water deposits to irrigate the surrounding land. The Banados region now exports much of Uruguay's rice crop, worth $80 million in U.S. dollars, which is beginning to create problems of desiccation of the lagoons. Furthermore, pesticides are used to protect rice crops and cases of pollution have been noted.

The lagoons are brackish, with little emergent vegetation, but the adjacent areas of botanical interest include freshwater marsh, shallow lakes, peat swamps, seasonally-flooded grasslands, and palm savannas. Butia palms (Butia yatay and B. capitata) have been protected since 1939 and form pure stands over an area of 70,000 ha (1 hectare=2.5 acres). There are typical marsh plants, members of the Cyperaceae, Juncaceae and Poaceae, mainly rushes (Scirpus californicus, S. giganteus), bulrushes (Typha spp.) and Zizaniopsis bonaerensis. There is also a wide range of psammophilous plants and extensive stands of the Atlantic pine (Pinus atlantica) along the coast.

In the swamps there are large colonies of coypu (Myocastor coipus) and capybara (Hydrochoerus hydrochaeris), while the threatened La Plata otter (Lutra longicaudis) and the giant river otter (Pteronura brasiliensis) are rather scarce. The typical small inhabitants of the swamps are the little water opossum (Lutreolina crassicaudata), the tuco-tuco (Ctenomys pearsoni), water rat (Scapteromys tumidus) and marsh rats (Holochilus magnus and H. brasiliensis). Two deer species also live in the swamps, the pampas deer (Ozoteceros bezoarcticus) and the marsh deer (Blastocerus dichotomus), which are restricted to the pampas of south-east Brazil, northern Argentina and Uruguay. Many animals, especially the coypu, have been commercially exploited for their fur. The FAO estimates that Uruguay earned $52 million in U.S. dollars between 1976 and 1988 from coypu skins and that the profits benefited 40% of rural families. Recently, however, there have been signs of overexploitation and there has been a dramatic fall in coypu populations and in the profits.

The Banados del Este wetlands are among South America's richest in waterbirds. At least a third of all the bird's recorded in Uruguay are found there. Of the 120 species normally present, there are at least 14 species of duck and three species of coot. The reserve's birdlife also includes many less common species, such as the red-legged seriema (Cariama cristata). The blacknecked swan(Cygnus melanocoryphus) and the coscoroba swan (Coscoroba coscoroba), breed within the reserve which is the northern limit to their range. There are also Muscovy ducks (Cairina moschata), blackheaded ducks (Heteronetta atricapilla), snowy egrets (Egretta thula), white-faced ibis (Plegadis chihi), black-winged stilts (Himantopus himantopus) and brown-hooded gulls (Larus maculipennis) breed in large numbers in the marshes. Banados del Este is also one of the most important zones in the southern hemisphere for the study of migratory birds such as the American golden plover (Pluvialis dominica), which breeds in the North American tundra and descends to the reserve to pass the southern summer. In the southern winter, other migratory southern hemisphere birds have been spotted, birds that have raised their young in Antarctica, the South Georgia Islands and the Falkland Islands, such as the black-browed albatross (Diomedea melanophris), the pintado petrel (Daption capense), the snowy sheathbill (Chionis alba) and several species of penguin. Biologists are examining the factors determining the survival of migratory birds in their nonbreeding range, in order to explain the observed changes in breeding numbers.

Management problems

The Banados del Este Biosphere Reserve is accessible by a road in good condition, and there is a field station for visiting scientists. It also the center of a large fishing industry that depends on the maintenance of water quality, and especially the balance between fresh and salt water. Of the 80 species of fish identified in the lagoons, 30 are commercially important while the others are exploited on a subsistence basis. The Laguna de Castillos is an important site for the sea shrimp (Penaeus platensis) to lay its eggs.

The reserve is increasingly threatened by the change in land use model of its surroundings. Theoretically, it is large enough to safeguard coastal ecosystems, but as 70% of the reserve is privately owned, it is proving difficult to enforce regulations. Stock-raising is giving way to rice cultivation and pesticides are now widely used. Attempts have been made to drain some lagoons and alter water levels in seasonally flooded zones to produce permanent agricultural land. Banados is a popular with Mexican and international tourists, and this activity requires regulation. Some spontaneous marginal settlements have occurred in government owned land. The legally protected butia palm (Butia capiata) is now seriously threatened by grazing animals.

A research program has been set up to tackle the most important problems. Researchers are working to improve dry season grazing for livestock, to intensify rice and soya cultivation and also to regulate the water levels in periods of flooding and drought. An avian biology program has been set up to monitor bird migration and reintroduce locally extinct species. This type of ecological research is important for the better understanding of temperate zone wetlands.

Plans for canals to drain the Banados del Este date back more than a hundred years to 1885. By 1978, two drainage canals had been built to drain 30,000 ha (1 hectare=2.5 acres) of land in order to dry out 3,000 ha by draining the water into a dam, in India Muerta. Government investment in the area has been channelled through the Comision Mixta para el Desarrollo de la Cuenca de la Laguna Merin, a corporation set up in the 1960s by Brazil and Uruguay. In 1986 the Commission obtained $27.3 million in U.S. dollars from the Interamerican Development Bank for electrification, the installation of water-pumping equipment and road improvement. These measures were designed to improve irrigation for the 80,000 ha around Laguna Merin. By 1988 there were proposals for further investment in water management, including a dyke along the right bank of the Rio Cebollati, the mechanisation of Estero de Pelotas, the construction of a 25 mi (40 km) long sump to drain water from the San Miguel region into Laguna Merin and a dyke to control flooding of the India Muerta reserve. According to a visit by representatives of the Ramsar Bureau, previous investment in drainage has led to major socio-economic costs. As an example, the increase in the capacity of the Andreoni canal has led to more debris on tourist beaches and has led to a decline in offshore fisheries by altering the delicate balance between fresh and salt water. The coypu industry has also declined due to the changes in its habitat, and the greater liability to flooding at certain times of year.

The case of the Donana Biosphere Reserve

When Donana National Park was created in 1969 with an area of 151 sq mi (392 sq km) it was Spain's largest protected area. Nine years later, Donana became one of the largest wildlife reserves in Europe when it was almost doubled in size to 293 sq mi (758 sq km). It was recognized as a biosphere reserve by UNESCO in 1980.

For thousands of years, Donana has been of strategic importance to hundreds of thousand of migratory birds which make the long journey every year between their nesting areas in Europe and wintering grounds in Africa. A region of low-lying land located at the southern tip of Europe, between the Guadalquivir River and the Atlantic Ocean, it acts as the final staging post before the sea crossing to the African continent. This, together with the great variety of biotopes and its great biological diversity, have made it one of the most interesting natural areas in Europe.

Characteristics and natural values

One of the most striking features of Donana is the variety of its habitats and landscapes. Approximately half of the reserve (the part nearest the Guadalquivir River) consists of mudflats and associated lagoons and creeks. This is Spain's most important wetland and it was designated as a zone of international interest and included in the list of Ramsar sites in 1982. The other half is slightly higher, although the entire reserve is below 131 ft (40 m) above sea level, and comprises dry habitats such as cork oak woods, matorral (scrub), pinewoods, dunes and beaches. Of the Guadal-quivir River's thousands of hectares of mudflats, only a few hundred are protected within the national park.

The mudflats are broken up by canos or creeks, corresponding to ancient tributaries of the Guadalquivir; the three principal creeks are the Travieso, Guadiamar and la Madre. Another feature are the lucios, round or ovoid, shallow lagoons which pepper the mudflats, only disappearing in the driest spells. The small ojos (literally eyes) or springs are usually permanent and do not dry up even at the height of the summer. There are also patches of raised ground, known as vetas or islets, which do not flood even in the worst winter rains. Likewise, the levees or paciles along the banks of the creeks and rivers are always above water. The lucios are some of the last water bodies to dry up and as such are of great ecological importance, acting as refuges in the months when the waters disappear from the rest of the mudflats. The islets and levees are a preferred nesting site for many species of wading birds, given their proximity to the water's edge and the ease with which chicks can reach the water to feed.

The appearance of the mudflats changes with the seasons. In August the area is arid and the mud turns into a baked, cracked pan. When the first rains fall in autumn, the lucios begin to swell and the earth and desiccated vegetation swiftly turn to mud. Throughout the winter the flats appear black as the previous year's vegetation is broken down and nutrients are released. In the first few days of spring the monotonous black is suddenly broken by patches of green when the first plants emerge; they soon carpet the entire flats, leaving only the lucios standing out as blue spots.

In the dry areas of the Park there are other lagoons complexes which also retain water throughout the driest periods of the year, acting as refuge and as breeding and feeding areas for a variety of waterbirds at different times of the year. At the height of the dry season when the flats dry out completely, these lagoons are home to vast concentrations of birds.

Some some 750 species of plants have been identified within Donana and these include two species new to science and another 45, largely originating from Africa, new to Europe. Donana's cork oak woods, now only found along the borders of the mudflats, are of immense importance and are the remains of the once very extensive vegetation that once covered the whole region. They separate the mudflats from the higher, drier terrain to the west and consist of cork oaks (Quercus suber) with an understory of ferns. In summer, a large number of birds live in and around these woods and some--herons and egrets--establish colonies of nests in the trees known as the pajareras de Donana.

The high ground or monte located in the northwest of the park, delimited by dunes to the south and mudflats to the east, is covered with Mediterranean matorral, a dry scrubby vegetation with scattered cork oaks. Its basic component is Halimium halimifolium, associated with Phillyrea angustifolia, ling (Calluna vulgaris), heath (Erica scoparia) and rosemary (Rosmarinus officinalis). In higher areas, juniper (Juniperus phoenicea), lavender (Lavandula stoechas), thyme (Thymus mastichina) and Halimi-um calycinum [= H.commutatum] dominate.

In the fresh marshes and saltmarshes sea club-rush (Scirpus maritimus), bulrush (Schoenoplectus lacustris), reedmace (Typha latifolia), and various species of rush (Juncus) grow. In the summer, the white flowers of the water crowfoot (Ranunculus baudotii) totally cover all stretches of permanent water. In higher and more saline areas, seablites (Suaeda) and glassworts (Salicornia and Arthrocnemum) grow.

Donana's coastline runs perpendicular to the prevailing southwesterly winds. The relentless Atlantic waves hurl sand up the shore, and the strong onshore winds blow it some way inland to form four or five rows of mobile dunes, usually composed of fine, white sand with small groups of stone pines (Pinus pinea) between the rows. Over a period of many years, a dune will gradually surround a pinewood and form the typical corrales, groups of pines surrounded by dunes. Slowly, the pines are weakened and are eventually buried by tons of sand. Once the dunes have passed, broken and mutilated trunks are left as a token of the wood that once grew there, and the process of colonization begins again. First, the seeds of small herbs are blown into the area between two dunes and take root. The roots of these first colonizers begin to bind the sand and to retain essential nutrients, so that gradually a primitive soil accumulates. The first plants tend to be sea holly (Eryngium maritinum), sea bindweed (Calystegia soldanella) and ling (Calluna vulgaris) and they help to consolidate the soil. Heavier pine seeds are then brought by the wind and establish themselves in the sparse soil formed by the first colonizers. Eventually, the original pinewood reestablishes itself.

This area is characterized principally by a system of mobile dunes and pinewoods. Plant communities on the dunes have Atlantic-North African affinities coupled with a notable degree of endemism. Marram grass (Ammophila arenaria) and Corema album are the commonest species. Around the lagoons, heaths of Erica ciliaris form, with dwarf gorse (Ulex minor), bracken (Pteridium aquilinum), as well as scattered trees such as the stone pine (Pinus pinea), cork oak (Quercus suber) and strawberry tree (Arbutus unedo). The Laguna del Taraje takes its name from the taray bushes (Tamarix gallica) growing on its banks. In the pinewoods, the undergrowth consists of heaths (Erica), cistus (Cistus), Osyris alba and mastic tree (Pistacia lentiscus). Further inland, there is a complex of stable dunes, known as gray or brown dunes depending on their age. Their coloration is due to the accumulation of darker organic matter as the dune ages. These dunes are typically colonized by ling (Calluna vulgaris), sea buckthorn (Hippophae rhamnoides), creeping willow (Salix repens), junipers (Juniperus communis, J. oxycedrus) and gorse (Ulex europaeus).

Two of the most interesting mammals found in Donana are the mongoose (Herpestes ichneumon), an introduced species which feeds mainly on rabbits and snakes, and the Spanish lynx (Lynx pardina). This species of lynx is a little smaller than the European lynx (Lynx lynx) and has a buff coat with small black spots and streaks, as well as distinctive ear tufts. It is endemic to the Iberian Peninsula. Rabbits form the greater part of its diet and its tracks are frequently seen in sandy areas in the early morning, evidence of its crepuscular and nocturnal activity. It frequents the pajareras during the breeding season. In 1992, a Spanish lynx captive breeding center, designed to hold eight animals, was established on the reserve in order to gain more information on the biology of the species and to investigate methods of breeding and reintroduction in the wild.

Other common mammals of Donana are wild boar (Sus scrofa), fallow deer (Dama dama), red deer (Cervus elaphus), small spotted genet (Genetta genetta) and red fox (Vulpes vulpes). The lagoons are inhabited by otters (Lutra lutra). The populations of these mammals are constantly monitored by the reserve's resident biologists and management practices are geared to maintaining viable populations. However, red fox numbers have grown dramatically over the last few decades, just as they have throughout the rest of Europe. Solutions to this recent increase in numbers are being sought because of their impact on breeding waterbirds.

Donana is home to most of the fauna normally associated with the Mediterranean, as well a few elements from North Africa and the rest of Europe which have moved down the Atlantic coastline. The most notable bird is the imperial eagle (Aquila heliaca adalberti) which nests in the pines. This predator par excellence feeds on rabbits, although when it has young in the nest it will also take reptiles, amphibians, and small waterbirds. It is distinguished from all other eagles by the light shoulder patches on its wings and, when seen from below in flight, its pale leading edge to the wings. The other breeding birds of prey are: short-toed eagle (Circaetus gallicus), booted eagle (Hieraaetus pennatus), Bonelli's eagle (H. fasciatus), buzzard (Buteo buteo), black and red kites (Milvus migrans, M. milvus), marsh harrier (Circus aeruginosus), osprey (Pandion haliaetus), kestrel (Falco tinnunculus) and hobby (F. subbuteo). Spanish hunting reserves or cotos are famed for their diversity of birds of prey. The crowns of old pines are favored breeding haunts of short-toed eagles and hobbies. Both ospreys and black kites nest in the upper parts of trees near water and feed on the profusion of fish they have on their doorsteps. The marsh harrier nests out of sight amongst the thick marsh vegetation and quarters the lagoons and marshes in search of small mammals and birds. Once they have bred, most of these raptors leave Donana and cross the Mediterranean at the Straits of Gibraltar to spend the winter in Africa. Only the buzzard, red kite and kestrel remain throughout the winter months.

One of the rarest breeding birds is the flamingo (Phoenicopterus ruber) which feeds on molluscs, crustaceans, insects, small fish, and algae filtered out from the mud by means of its extraordinary curved bill. The purple gallinule (Porphyrio porphyrio) breeds in good numbers amongst the reeds, a habitat also favored by the ferruginous duck (Aythya nyroca) and white-headed duck (Oxyura leucocephala). Slender-billed gulls (Larus genei), whiskered terns (Chlidonias hybrida) and gull-billed terns (Gelo-chelidon nilotica) breed in small colonies on dry mudbanks and islands. Black terns (Chlidonias niger) build floating nests in shallow marshes and lagoons and breed in colonies. The stone curlew (Burhinus oedicnemus) breeds in the reserve's dry, heathy areas, along with several species more characteristic of desert and steppe habitats, such as calandra larks (Melanocorypha calandra) and pin-tailed sandgrouse (Pterocles alchata). Ruddy shelduck (Tadorna ferruginea) excavate nesting holes in sand dunes so that their young can make their way to the sea within a few hours of hatching. Gray herons (Ardea cinerea), spoonbills (Platalea leucorodia), night herons (Nycticorax nycticorax), squacco herons (Ardeola ralloides), cattle egrets (Bubulcus ibis) and little egrets (Egretta garzetta) are the typical residents of the pajareras or nesting colonies in the tops of cork oaks.

The marshes lie on the west Europe to west Africa migration route and is a vital winter habitat for many species of waterfowl, such as the 40,000 graylag geese (Anser anser), and tens of thousands of teal (Anas crecca), pintail (A. acuta), shoveler (A. clypeata) and wigeon (A. penelope).

Management problems

Donana was one of the favorite hunting reserves of Spanish kings such as Philip IV, Philip V, and Alfonso XIII. It was owned by the Duchess of Alba and formed the background to her portrait by Goya. The Donana Palace remains a testimony to the area's exalted past. Even today, the tradition of hunting wild boar is still practiced; mounted hunters use long spears and dogs which cling onto the boar to prevent it escaping. Only male boars are killed and their tusks are kept as trophies. Carp (Cyprinus carpio) and eels (Anguilla anguilla) are common and both form part of the basic diet of many of the reserve's predators. They have long provided sport for Spanish royalty, that has been practiced for a long time in this region.

Even though Donana has been afforded a high degree of protection under the status of a national park, an important part of its area is still in private hands and, moreover, many people believe that its days are numbered. Its contact with the sea has been decreased by the construction of hotels, the water table has been altered by intensive cultivation and drainage, and water systems have been polluted by fertilizers and pesticides. Fortunately, earlier plans for massive groundwater extraction have been scaled down. However, the latest threat is the proposed construction of two golf courses, together with luxury houses and hotels on the reserve's dune systems, a development which would require large amounts of water for irrigation.

The Guadalquivir River basin occupies some 22,107 sq mi (57,257 sq km), almost all within Andalusia. Eight reservoirs are planned along its course and those of its tributaries. Of these projects, the most serious is the Guadiamar reservoir on the Guadalquivir itself. It is difficult to say exactly how much water can be taken out of the river without seriously affecting Donana. In wet years, the mudflats become completely submerged during the winter, whereas they remain dry during years of lower rainfall. In addition to this, vast quantities of water are extracted from the watercourses which feed the reserve in order to irrigate strawberry crops further up the Guadalquivir basin. Equally worrying is the extraction of ground water for use in adjacent tourist development. Groundwater supplies are particularly difficult to monitor and for this reason they may in fact be critically overexploited over a number of years or even decades until land desiccation is finally noticed. By this time it will probably be too late for countermeasures to be taken.

Over the last twenty years Donana's wetlands have shrunk from some 772 sq mi (2,000 sq km) to just 104 sq mi (270 sq km) today. Conservationists have become concerned about the effects of reservoirs and water extraction and have commissioned a study to assess the effects of hydrological changes and to predict the future of Donana. The preliminary results have been alarming. A 1986 study revealed a drop in the water table of 66 ft (20 m) in some parts of the reserve. In fact, the water table has fallen so much in recent times that there is now a nett seepage of saltwater inland from the coast, bringing with it a gradual salinization of soils. The breakage (in April 1998) of a dam retaining mining wastes (five million [m.sup.3]) at Aznalcollar, upstream from the Guadiamar, caused the contamination of a lot of land near the park. As a result, sublethal quantities of heavy metals have been detected in many sedentary and overwintering waterbirds.

2.3 Biosphere reserves greatly modified by human action

Not all of the world's coastal biosphere reserves are found in remote areas. Some reserves, above all in Europe and North America, are under pressure from nearby large centers of population. A good example is the Wadden Sea Biosphere Reserve in northern Europe.

The case of the Wadden Sea Biosphere Reserve

The Wadden Sea is a vast tidal area extending in an arc along the North Sea coasts of Denmark, Germany, and the Netherlands. It covers the coastlines of the provinces of Noord-Holland, Friesland and Groningen in the Netherlands, Schleswig-Holstein in Germany, and Ribe and Sonderjylland in Denmark. The Wadden Sea is unique and starkly beautiful. It acts as a transition zone between sea and land; of the 320,000 ha (1 hectare=2.5 acres) of open sea, tidal channels, sandbanks, saltmarshes and freshwater lagoons, 160,000 ha are exposed at low tide. It is protected from the open sea by a chain of around 50 islands and sandbars covering a further 40,000 ha. 60% of the whole area of 360,000 ha, is in Germany, while 30% is in the Netherlands and the remaining 10% in Denmark. It is, therefore, the largest unbroken stretch of intertidal mudflats in the world and constitutes 60% of all tidal flats within Europe and North Africa.

Given the progressive disappearance of coastal wetlands and mudflats in the rest of Europe, the enormous expanses of the Wadden Sea are doubly important. The first protected areas were declared in the Netherlands in 1967 and over the next 20 years other important sectors of the Wadden Sea were given protection, mostly as nature reserves. By 1990 the Niedersachsisches Wattenmeer and Hamburgisches Wattenmeer National Parks within the German sector, and the Vadehavet National Park in the Danish sector were declared. The German and Dutch sectors have subsequently been recognized as international biosphere reserves. The whole of the Dutch zone, along with a part of the German and Danish zones, has been included in the Ramsar Convention list as wetlands of international importance in recognition of their immense value for water birds.

Characteristics and natural values

The Wadden Sea is a harsh environment; the extreme fluctuations in temperature, salinity and humidity force the Sea's inhabitants to be highly specialized. Those species which have adapted also prosper along a wide range of other European coasts. In terms of biomass, the Wadden Sea rivals tropical jungles and is one of the most productive ecosystems in the world. The primary production has been estimated to be around the same as in a field of barley and in fact doubles that of the North Sea and triples that of the Atlantic. The key to explaining this remarkable productivity is the enormous amount of nutrients brought down by rivers and redistributed twice a day by the tides. Over a billion [m.sup.3] of seawater loaded with 35 million tons of common salt, 200 tons of sulphates, 200 tons of phosphates, and large amounts of organic matter flood into the Marsdiep, Den Helder and Texel bays with every rising tide.

The landscape, sedimentary in origin, is totally flat and the highest point is a mere 66 ft (20 m) above sea level. Rising sea levels are constantly pushing the coastline landwards, but this is counteracted by a constant reshaping of the coastline by currents and silt deposition. The Wadden Sea is a dynamic ecosystem that changes from month to month and from year to year.

The Wadden Sea was formed by the relative rise in sea level in northwest Europe which occurred after the last ice-age. This was a consequence of both the subsidence of the continental plate as the melting of the large areas of ice and the compaction of the sediments deposited in the area by the copious rivers that flow into the North Sea. The relative rise over the last century in the Wadden Sea has been about 2 in (5 cm), although in the German sector the figure it has been as much as 10 in (25 cm). The change in sea level has not occurred uniformly over the whole of the Earth's surface owing to the buckling caused by changing ice and water loads.

The physical features of the Wadden Sea are marine in origin. Its fine sands and muds are constantly being eroded, transported and deposited. The exact extent of these processes depends on temperature, rainfall, evaporation, winds, tides and biotic factors. Nett sedimentation is occurring in the Wadden Sea as deposition rates have managed to keep pace with the rising sea level; as a result the sea's shape has changed little over the last 6,000 years. Geomorphologists calculate that nett mud deposition in the Wadden Sea is between one and three million tons annually. In some areas of sedimentation, a number of underwater valleys running from the coast to the limits of the Wadden Sea, some up to 82 ft (25 m) deep, have been carved out. These were formed by rocks and gravels dragged to the bottom of the sea as the glaciers melted. Fifty years ago the Frisian islands were thought to be the remnants of a long spit, now fragmented by the force of the sea. Recent studies of sediment cores favor the theory that each one is a separately developed beach barrier formed by coarse sand transported parallel to the coast. The islands are, as time passes, slowly migrating landwards.

Along with the Wadden Sea, one of the most important habitats in the Netherlands is the almost uninterrupted dune chain running along the coast. The dunes began to form about 7,000 years ago and until 400 a.d. were covered by vegetation that included extensive forests. Severe weather conditions, as well as deforestation by humans from 1000 onwards, weakened the dunes as a sea defence and large-scale flooding took place. During this period the dunes all but disappeared, and it was not until after a new cycle of dune formation had begun that a well-formed dune system reappeared around 1600. Since the turn of the last century, the Dutch have being trying to artificially stabilize and fix the dunes. At first the dunes, wherever they extended inland, were cultivated or used, above all, for pasturing sheep. In recent times these areas have been given over to tourism and leisure and, in some areas, to nature reserves, although the role of dunes as physical defences against the sea has not been neglected. Another important function of the dune chain is water purification. Despite being highly contaminated by toxic industrial waste and domestic sewage when it reaches the Netherlands, the Rhine is the principal source of domestic water supplies for various large Dutch cities. As the water drains through them, the dunes act as gigantic filters, sifting out pollutants, making it once more drinkable.

The most distinctive characteristic of plant communities growing in saltmarshes is zonation of the vegetation. The frequency and length of time each zone is submerged determines the species which are found in each community. Certain plants have adapted to life in highly saline conditions and some such as the saltwort (Salsola kali), sea sandworts (Honckenya peploides) and sea purslane (Halimione portulacoides) have fleshy, succulent leaves. Few flowering plants can survive continual submersion by seawater, although two species of eel-grass (Zostera) that can survive are very common in the tidal mudflats of the Wadden Sea. Also found here are two species of cord-grass (Spartina) and dozens of seaweed and hundreds of micro-algae. Townsend's sea-grass (Spartina x town-sendii was first discovered in 1927 and is a hybrid of two species of the same genus, one North American and the other European. Since then this hybrid, more vigorous than the original species, has colonized large areas of Europe's exposed mudflats. Its hardiness, rapid growth and ability to bind the substrate and accumulate large amounts of sediment mean it is used to stabilize sediments.

The first true land plant found in marshes is the glasswort Salicornia ramosissima, which sometimes dominates the flats, excluding all others species. It is a low-growing, fleshy plant and individuals crowd together, trapping large amounts of silt and mud amongst their stems and thus contributing to raising the level of the soil and to the formation of drier, more terrestrial communities.

Salt marshes are covered by halophilic vegetation and around 30 species of angiosperms. The dominant species are common salt-marsh grass (Puccinellia

maritima), red fescue (Festuca rubra), glasswort (Salicornia ramosissima [= S. europea]) and sea aster (Aster tripolium). Transitional areas between marshes and dunes support approximately 100 plant species, although very little vegetation grows in tidal channels.

Coastal dunes are consolidated as a result of colonization by three specialized grass species: sand couch (Elymus farctus), marram grass (Ammophila arenaria) and lyme grass (Leymus [=Elymus] arenarius). Their form of growth allows them to live in highly saline conditions amongst shifting grains of sand. They are perennials and their roots and lateral shoots grow very quickly through sand, helping to bind the dunes: marram grass shoots can grow through many meters of sand. Other typical inhabitants of the primary dunes are the curled dock (Rumex crispus), the sea campion, with its delicate white flowers (Silene vulgaris), the sea rocket (Cakile maritima), and the sea holly (Eryngium maritimum). As the dunes stabilize and age, they are often colonized by ling (Calluna vulgaris), sand sedge (Carex arenaria), and lichens such as Cladonia. Much has been written on the algae, macrophytes, phytoplankton and benthonic organisms of these environments.

Many plant species are endemic to the Wadden Sea, either because they evolved there and have never extended their range beyond it, or because they have become extinct in other parts of Europe as a result of human-induced changes to coastal environments.

Although there are only about 250 animal species adapted to the extreme environmental conditions of the Wadden Sea mudflats, all are extremely abundant. For most marine mammals, the Wadden Sea is not a suitable habitat given its shallowness and extensive tidal flats. The only common medium-sized mammal is the common seal (Phoca vitulina). The porpoise (Phocoena phocoena) and the bottle-nosed dolphin (Tursiops truncatus) are sometimes seen; the latter was much more common before the Zuiderzee was closed off in 1938, eliminating the races of herrings that used to spawn there. The ringed seal (Phoca hispida), harp seal (Pagophilus groenlandicus), hooded seal (Cystophora cristata) and the gray seal (Halichoerus grypus) are stragglers to the area whilst the walrus (Odobenus rosmarus) has occasionally been recorded.

The Frisian Islands have a rich freshwater and terrestrial fauna due to their varied habitats and relative isolation. There are large numbers of molluscs despite the islands' lack of calcium. Over 1,500 species of arthropod have been counted. They are especially hardy with high reproductive rates as well as many mechanisms for coping with life in saline environments subject to immersion. Many of the 20 species of fish in the brackish and fresh water pools have been introduced by humans. The islands are also a stronghold of the natterjack toad (Bufo calamita), a species which has become threatened throughout the countries bordering the Wadden Sea. 177 species of bird breed there and the islands are also home to 34 species of land mammal.

The Wadden Sea plays a vital role in the life history of over 50 species of bird. Every year an average of 10 million birds, from an area 100-125 times bigger than the Wadden Sea itself, stop here on their migratory route between their Arctic breeding grounds in North-America, Greenland and Siberia and their wintering areas in Europe and Africa. Some stay only a short time whereas others spend a number of weeks whilst they molt and fatten up before continuing their journeys to destinations perhaps thousands of kilometers away. The autumn migration begins in the second half of June with the arrival of the first spotted redshanks (Tringa erythropus) together with small numbers of other species. July sees the arrival of large numbers of gray plovers (Pluvialis squatarola), knots (Calidris canutus), 330,000 dunlins (C. alpina), 93,000 bar-tailed godwits (Limosa lapponica), 122,000 curlews (Numenius arquata), 45,000 redshanks (Tringa totanus), greenshanks (T. nebularis) and turnstones (Arenaria interpres), along with black-headed and common gulls (Larus ridibundus and L. canus). 290,000 oystercatchers (Haematopus ostralegus) arrive mainly in August, whilst wigeons (Anas penelope) and pintails (A. acuta) arrive from September onwards. Brent and barnacle geese (Branta bernicla and B. leucopsis) can be seen in great numbers in October, and there is an influx of shelduck (Tadorna tadorna). The last to arrive at the end of October or beginning of November are the red-breasted mergansers (Mergus serrator) and goosander (M. merganser).

Despite the fact that the best protected areas are to be found in the Dutch part of the Wadden Sea, the Danish sector is very important for shelduck (Tadorna tadorna) and roosting mallards (Anas platyrhynchos), teal (A. crecca) and shoveler (A. clypeata). The German sector is the largest and is important for millions of ducks, gulls, and wading birds. Virtually the whole European population of shelducks molts on Knechtsand and Trischen islands. The islands in the Wadden Sea are particular important for a number of breeding species such as the avocet (Recurvirostra avosetta), Kentish plover (Charadrius alexandrinus), spoonbill (Platalea leucorodia) and marsh harrier (Circus aeruginosus) which are rare throughout the rest of northern Europe.

The tidal channels and mudflats hold a wide and productive assembly of invertebrates. Some of the more common species include the copepod Temora longicornis, two species of jellyfish, the common jellyfish (Aurelia aurita) and Rhizostoma pulmo, polychaetes, such as lugworms (Arenicola marina) and ragworms (Nereis diversicolor), mussels (Mytilus edulis), cockles (Cerastoderma edule), the Baltic tellin (Macoma balthica), the sandgaper (Mya arenaria), the common shore crab (Carcinus maenus) and the common shrimp (Crangon crangon). Mussels, cockles, sandgapers, baltic tellins and lugworms make up 80% of the benthic fauna and are the staple diet of many birds and fish. With the exception of some geese and ducks, all birds found in the Wadden Sea are carnivores.

The average weight of the benthic biomass has been calculated as 27 g ash-free dry weight/[m.sup.2] and it produces 20 g/[m.sup.2]/year plus 5 g of gametes. By means of a formula relating basal metabolic rate to body weight, and a factor relating food consumption to basal metabolic rate, the annual food consumption of birds has been calculated as being between 3.7 and 4.3 g ash-free dry weight/[m.sup.2]. At first sight it may seem that there is plenty of food for the seabirds of the Wadden Sea. Nevertheless, demersal fish consume between 3 and 5 g/[m.sup.2]/year and benthic invertebrates consume a further 3 or 4 g/[m.sup.2]/year. Thus, consumption is at least 10-12 g/[m.sup.2]/year. Fishing for cockles and mussels represents another 1 or 2 g/[m.sup.2]/year and so the difference between consumption (11-14 g) and production (20 g) is between 6 and 9 g/[m.sup.2]/year. However, given that part of the benthic fauna lives too deep for birds to reach and that invertebrate mortality is high during winter freezing, food is, in fact, in short supply. This scarcity leads to competition between birds and various adaptations and feeding strategies have evolved; a variety of bill lengths and shapes permit different species to exploit different food sources.

Approximately 100 species of fish have been recorded in the Wadden Sea, 22 of them common. Five of these species were once abundant but have begun to decline over the last 10-30 years. Not all fish use the Wadden Sea in the same way: life cycles vary and some fish are resident, some leave the area to spawn or during extreme winter cold, some visit as adults whilst others enter the area to spawn. Many species spawn in the North Sea; the fry make their way to the Wadden Sea when they hatch and spend their juvenile stages there. They find protection from adverse conditions at sea, plenty of space, warmer water, and an abundant food supply. Studies have shown that roughly 40% of the herring, 50% of the sole, and 80% of the plaice in the North Sea originate from nurseries in the Wadden Sea. As these fisheries generate million of pounds per year, the economic value of the Wadden Sea to North Sea fisheries is clear.

Some invertebrates and fish use tidal currents to move in and out of the Wadden Sea. This evolutionary and behavioral adaptation demonstrates that the coastal system must have been stable for a relatively long period of time. Although there is almost no fishing in the Danish sector, fish species such as eels (Anguilla anguilla), smelts (Osmerus eperlanus), various flatfish, shrimp and a number of other species of bivalves and crustaceans are caught in the German and Dutch sectors. Unfortunately, the flourishing 19th century oyster fishery was ruined by over-exploitation. In the 1950s mussel culture began to be developed and in the Dutch sector alone, 70,000 tons are harvested annually.

Human modification

Since time immemorial humans have exploited the Wadden Sea. Fishing, hunting and agriculture have been practiced since the beginning of recorded history. More recently it has been used for military training, scientific research and tourism. Pliny the Elder in his Historia Naturalis described it as a place of "pitiable people living on man-made islands, hunting fish which escape to deep waters at low tide with nets fashioned from reeds and rushes." Archaeological finds in the form of weirs, fykes, dip, and seine nets have revealed ancient technologies which were still in use in living memory.

Human settlements on the islands' limited land were necessarily dependent on fish from the Wadden Sea and on the great herring shoals of the North Sea. Fish were caught by hook and line. In the 15th century the inhabitants of the barely fertile Pleistocene islands of Amrum and Sylt (in the modern-day Netherlands) lived off the herring. However, catastrophic loss of life and ships in 1610 brought fishing to a standstill. On the island of Texel in 1514, roughly 500 men (from a total of 750 families) fished the seas for haddock, cod and plaice. In 1753 almost all of the workers from Borkum, Ameland and Terschelling worked for whaling companies and lived in Hamburg, although once whaling finished at the end on the 18th century, these men shifted to for the merchant navy.

In the shallower waters of the Wadden Sea, subsistence fishing was carried out using mudsledges. Records dating from the 11th century show the legal regulation of commercial herring fisheries. By the 12th century net sizes were controlled by means of a silver coin that had to pass "easily" through the net's mesh, and there was a strict limit on the number of nets per crew member.

The construction of dykes in some parts of the Wadden Sea has irreversibly altered parts of this coastal ecosystem. Some zones have been cut off by embankments, and estuaries have been closed off from the sea by dykes to create new agricultural land (polders) on the fertile sedimentary soils. Since 1950 over 160,000 ha (1 hectare=2.5 acres) have been reclaimed at the expense of the saltmarshes that play a very important part in this ecosystem. Denmark lost a quarter of its 3,200 ha of saltmarshes when it constructed dykes in 1980. The effect on wildlife has been monitored by the Danish National Agency for the Protection of Nature, Monuments and Sites. Since the construction of the dykes, geese numbers have dropped by 99%, waders by 90%, and ducks by 30%. Previously, the area had been of international importance for eighteen species of wildfowl and waders, in comparison with only eight species today.

The German sector of the Wadden Sea is most threatened by plans to build dykes. The Schleswig-Holstein Government proposes building 6 mi (9 km) of dykes across the Nordstrander Bucht, and a further 8 mi (12 km) long dam from the coast to the island of Pellworm that would reclaim 3,400 ha of mudflats and saltmarshes. 1,200 ha have already been lost in Nordstrander Bucht trough the construction of a dyke. The environmental protection group Deutscher Naturschutz (DNS) estimates that unless a consensus is reached between ecological values and economic exploitation, at least 4,000 North Sea plant and animal species will be threatened by dyke construction, as well as increased tourism, pollution, intensive farming, and industrialization.

Management problems

The main problems facing the conservation of the Wadden Sea are dyke construction, port and industrial developments, pollution and mass tourism, as well as the constant threat to wetlands of drainage and overgrazing. In Germany, farming, fishing and the constant traffic of small boats are having negative effects on central sectors of the Wadden Sea. In 1988, moves were made to introduce new regulations in light of the growing pressure from motor boats and yachts in central areas. New norms had to be introduced as a result of the increase in large scale fishing by Dutch companies.

The Wadden Sea biosphere reserves are controlled by various state and provincial agencies and non-governmental organizations. In Germany, where only a small part of the Wadden Sea is included in a biosphere reserve, most of the land is owned by the central government and a few other areas are property of provincial and local government and of private conservation organisations. In the Netherlands 15% of the core area (13,000 ha) is owned and managed by conservation societies such as Natuurmonu-menten, and the rest is administrated by the state. Management would improve if the biosphere reserve within the three countries were to collaborate in their management.

Traditional resource uses still practised include fishing and harvesting of bivalves (especially mussels) and of lugworms. Studies show that current levels of lugworm harvesting are not detrimental to bird populations. More concern has been raised over the disturbance to feeding birds caused by the presence of people digging for lugworms. Many of the small islands in the Wadden Sea have been created artificially for wildfowl and shellfish production. The area's fisheries harvest shrimp, mussels, clams, and smelt.

The most active management is in coastal saltmarshes and dunes. In the Skallingen Peninsula in Denmark, and in many other Wadden Sea wetlands, vegetation is grazed to create better conditions for waterbirds. Jorchand Island in the southern sector of the Danish Wadden Sea is being protected against erosion to safeguard bird colonies. Great efforts have been made to create a high foreland in front of all sea dykes to break the force of the waves and thereby reestablish saltmarsh zones. Herring gull (Larus argentatus) populations have become a problem in many parts of the Wadden Sea and are being controlled to reduce their impact on young waders and terns.

The Wadden Sea biosphere reserves have been carefully delimited so that there are no permanent inhabitants within their boundaries. In addition, there is no public access to the core area in Germany. Fishing is strictly controlled and all farming, except grazing to maintain coastal defences, is prohibited. Most Dutch coastal reserves are closed to the public, at least during the breeding season. Outside the core area some activities such as mussel culture are allowed, subject to rigorous control. The buffer zone can only be farmed in a way that respects wildlife and the public is excluded from the most sensitive sites. Breeding colonies of birds and seals resting areas are protected by strict wardening. In transition areas, certain economic activities such as sand extraction, harbor development and recreation are permitted. Although oil exploitation is generally not allowed, drilling licences have been granted in Mittelplate and Hakenseland in Germany, but strict precautions are taken to prevent possible oil spills.

The Wadden Sea borders one of the world's most polluted and industrialized areas. The risk of contamination by industrial residues or domestic waste is high. In fact, the Wadden Sea is affected by heavy metals and other toxic substances, as well as by eutrophication caused by nitrates and phosphates carried by rivers, from the North Sea and from the air. Nutrients are essential for the area's productivity but excess nitrogen and phosphorus causes oxygen deficiency, and may lead to the death of many organisms in the same way they do in eutrophic lakes and rivers.

Despite the relatively low concentrations of organic contaminants and heavy metals in the seawater, they accumulate in sediments and may reach concentrations a million times higher in organisms at the top of the food chain, such as seals and birds of prey. Circumstantial evidence suggests that polychlorinated biphenyls (PCB) originating from hydraulic systems cause of sterility in seals. It has also been shown that combinations of toxic substances attack the immune systems of seals and other animals, making them more susceptible to infections and outbreaks of disease.

High concentrations of contaminants are discharged by the rivers Elbe and Rhine. Fifty percent of the Rhine's waters flowing into the sea at Rotterdam end up in the western part of the Wadden Sea, whereas the Elbe's waters flow into the northern sectors. Furthermore, the Wadden Sea lies alongside one of the world's busiest shipping routes. The continuous discharge of oil and chemicals from ships in the North Sea is very harmful in the long term. The danger of accidents involving ships carrying oil and petroleum products is always present and would be catastrophic for the whole region.

The uniqueness and beauty of the Wadden Sea's landscapes and the recognition of its importance for waterbirds is beginning to attract tourists. Over 30 million people spend at least one night there during the holiday season and thousands of workers find summer employment in the tourist industry. The attractions include beach activities such as sailing, windsurfing and waterskiing, as well as hunting, angling and nature tourism. All these activities owe their existence to a series of semiwild open spaces and therefore to the natural reserves and other protected areas. About 25,000 boats, 300,000 anglers and 12,000 people on foot visited the area in 1980. Some cities, for example Harlingen in the Netherlands, are beginning to earn more from tourism (campsites, hotels, and all the other necessary infrastructures) than from manufacturing industry. German tour operators have built 30 information centers and a daily Wadden Sea Newsletter is published by the Common Secretariat. Yet mass tourism also creates environmental problems: the most common problems usually turn out to be the trampling of vegetation, disturbance of breeding birds and overhunting. New infrastructures often cause pollution and affect ground water levels, as well as requiring land to be drained before construction.

The Dutch-German-Danish Wadden Sea is a single ecological entity, and many of the factors threatening it are of a transboundary nature. Trilateral cooperation between the Wadden Sea states is essential to ensure its adequate conservation, and its sustainable development. The three states have been cooperating since the 1970s. The Joint Declaration on the Protection of the Wadden Sea was signed in 1982. The three states involved have agreed to cooperate to implement international treaties on conservation such as the Convention for the Conservation of European Wildlife and Natural Habitats (Berne 1982), the Ramsar Convention (Ramsar 1971), the Convention on the Conservation of Migratory Species (Bonn 1979) and the EC Bird Directive (79/409/EC). The declaration protects the nature of the Wadden Sea and puts an emphasis on seal resting and breeding sites and on bird roosting, feeding, breeding and molting sites. It also concentrates on pollution, an issue that can only be dealt with on a regional scale. In The Hague in 1990 the Wadden Sea states urged that phasing out of PCBs and the reduction of other pollutants within a few years.

In 1987 the Wadden Sea states established the Common Wadden Sea Secretariat, designed to strengthen cooperation to protect the area, by collecting information on threats and conservation efforts, by analysing this information and the legal structures concerning protection in each country, by disseminating information about the region, and by supporting scientific programmes and trilateral meetings and conferences. The Wadden Sea states hold intergovernmental conferences every three years in which nongovernmental organizations are encouraged to participate.

314 This untouched and beautiful coastal landscape, with its large granitic blocks encrusted with lichens and compact layer of shrubs, is the southernmost point of Australia--Tongue Point. It is in the Wilson's Promontory National Park, made one of Australia's first two protected zones in 1905. It serves as a symbol of the many lost riches and those still found along the world's coastlines.

[Photo: Jean-Paul Ferrero / Auscape International]

315 Countries that have signed the Ramsar Convention, with the number (in brackets) or areas assigned and location on the map of protected areas of more than 20,000 ha (1 hectare=2.5 acres), as of June 1993 (see vol 9, pp. 440-441).

[Drawing: Editronica from several sources]

316 Preserving certain habitats is essential for the survival of some species, such as the Hawaiian monkseal (Monachus schauinslandi), a species restricted to the small western islands of Hawaii. It and the Caribbean seal (M. tropicalis), which is almost extinct, are the only completely tropical seals. Similar in anatomy and physiology to other seals, the Hawaiian seal is only active at night, fishing, and during the day it rests immobile on cool rocks or soft sand. Formerly heavily hunted, it has now disappeared on Midway and there are only 1,000 individuals on the Hawaiian Islands.

[Photo: Francois Gohier / Miguel Monge]

317 The ruins of the Mayan temples of Tulum on the shores of the Caribbean form part of the historical heritage of the Sian Ka'an Biosphere Reserve. These temples are from the post-classical period (12th-16th centuries) and were thus still in use when the first Spanish conquistadors arrived.

[Photo: Ankh / Miguel Monge]

318 Cenotes are big karstic dolines, sometimes in the open air, sometimes in underground caverns, that perforate the calcareous structure of Sian Ka'an.

[Photo: Ankh / Miguel Monge]

319 One of the most spectacular birds of the Sian Ka'an wetland is the jabiru (Jabiru mycteria), unmistakable for its white plumage, dark black featherless head, neck, and beak. The neck also lacks feathers and is bright red.

[Photo: Xavier Ferrer & Adolf de Sostoa]

320 Palm trees have long played a fundamental role in Yucatan Mayan culture. One of the most common uses was the construction of palapas, traditional cabins made of nakax (Coccothrinax readii) and of the seriously depleted "chit" (Thrinax radiata), whose leaves can be seen drying in the photo. T. radiata is the only member of this genus found in Yucatan, where it occurs exclusively on alkaline soils in semievergreen forests and coastal dunes. Its solid, strong trunk is used to construct the basic structure for cabins and the leaves make resistant roofing. They are also used to make lobster pots to catch lobsters because they resist salt water very well. Coc-cothrinax readii is a palm tree endemic to Yucatan that prefers drier conditions and is more frequently found in forests. Its straight trunk is ideal for making panels and partitions and has been widely used in hotel construction along the coast. During the 1980s Mayan-style hotel and house construction led to severe depletion of the palms in the peninsula's tropical forests. The vulnerable kuka palm (Pseu-dophoenix sargentii) is used more for ornamentation than construction, and is now listed as endangered. Palms are ideally used on a small scale, but their slow growth makes them unsuitable for intensive extraction.

[Photo: Xavier Ferrer & Adolf de Sostoa]

321 The coastal waters of Sian Ka'an include rich fisheries and traditional lobster (Panulirus argus) fishing in Ascension Bay is the basis of the economy of the reserve's inhabitants. There is fishing within Espritu Santo and Ascension bays and along the coral reef that protects the entrance to the reserve, and the lobsters caught are generally juveniles. In 1985 and 1986 the extensive lobster tagging program by the Amigos de Sian Ka'an and the University of Mexico found that they disperse from the bay as they grow, into deeper waters near the reef. Studies of larval recruitment and population dynamics have been performed, as well as research into factors like water temperature, salinity, turbidity, wind and wave direction and lunar phases to design a plan for lobster management. Unfortunately, in 1988 Hurricane Gilbert destroyed a system of aquaria for the study of post-larval lobsters and their behavior. In addition to improving the fishery industry of this species, work is under way to identify other species of potential commercial value in order to diversify use of marine resources.

[Photo: AGE Fotostock]

322 Wetlands and grazing lands are a constant feature of the more human-modified parts of the Banados del Este Biosphere Reserve, as can be seen in this splendid landscape in the Rocha area.

[Photo: Xavier Ferrer & Adolf de Sostoa]

323 Hummingbirds are unforgettably beautiful, mobile and colorful. This one, Hylocharis chrysura, is feeding from the flowers of the ceibo, or coral-flower (Erythrina crista-galli), in the wetlands of Uruguay or Argentina, such as Banados del Este.

[Photo: Xavier Ferrer & Adolf de Sostoa]

324 The coypu (Myocastor coipus), a rodent mistakenly called "otter" by local people, is abundant in the Banados del Este area. It is much sought after for its fur and suffers from over-hunting.

[Photo: Xavier Ferrer & Adolf de Sostoa]

325 Donana's marshes stretch as far as the eye can see over a large part of the Guadalquivir's immense deltaic plain in western Andalusia, which leads to the Atlantic but has a Mediter-ranean climate. A few fallow deer (Dama dama) can be seen grazing in the foreground among the rushes.

[Photo: Javier Andrada]

326 The spoonbill (Platalea leucorodia) is possibly the most representative bird of the Donana marshes because it is a constant inhabitant of the crowns of the cork oaks (Quercus suber) where it builds its nests.

[Photo: AGE Fotostock]

327 One of most unusual mammals found in Donana is the African mongoose (Herpestes ichneumon), native to north Africa, sub-Saharan Africa, and Asia Minor. It is found in Europe in a few places, and all in the south of the Iberian Peninsula, and probably as introductions. It was introduced to Donana some years ago. The African mongoose, like all other members of its family, is a great predator of small rodents and snakes. However, contrary to popular belief, no species of mongoose is immune to poisonous snakebites. The mongoose's agility and rapidity ensure it wins its battles with snakes.

[Photo: A. Camoyan / Incafo]

328 Known locally as corrales, these clumps of stone pines (Pinus pinea) are found on the relatively clayey soils behind the dunes. However, the progression of the dunes gradually swallows up the corrales. The sand first kills the trees and then completely buries them. The empty space left behind by the dune advance can then be recolonized by pines and form a fresh corral. The next invasion of sand will continue the process in a cycle that lasts several decades.

[Photo: Teresa Franquesa]

329 The Rocio pilgrimage is the most traditional of all the festivals held in and around Donana. On the day of the Virgin of Rocio (rocio means dew) thousands of pilgrims from the villages of the area, grouped in brotherhoods with symbols and banners, head for the sanctuary of Our Lady right in the heart of the marshes.

[Photo: AGE Fotostock]

330 A view of the vast salt flats of the Wadden Sea Biosphere Reserve. In the foreground various halophilic plants such as the gray-leaved sea purslane (Halimione portulacoides), a few sea-lavenders in flower and glassworts (Limonium, Arthrocnemum) can be seen.

[Photo: Jan van de Kam / Bruce Coleman Limited]

331 Terschelling is the second largest island in the Dutch Wadden Sea. Two thirds of its 12,000 ha (1 hectare=2.5 acres) are in a semi-natural state. There are three natural reserves: Koegelwieck (250 ha), Noordvaarder (650 ha) and Boschplaat (4,400 ha). Boschplaat, in the eastern end of the island, received the Council of Europe Diploma for Nature Conservation in 1970 and is only occupied by the cattle that graze the 300 ha of dunes. 4,300 people live on the island and many depend on tourism and thus live indirectly off the natural reserves. The other two reserves consist largely of dunes with acid soils and a rich flora, used as a staging post for wading birds. Access to the three reserves is unrestricted, except for the military range at Noordvaarder and the Boschplaat reserve during the summer. The island's rich, varied vegetation has been well studied. The saltmarshes are inhabited by species such as glasswort (Salicornia ramosissima), red fescue (Festuca rubra) and distant sedge (Carex distans). Behind the dunes sea buckthorn (Hippophae rham-noides) and crowberry (Empetrum nigrum) shrub. In and amongst the dunes a number of interesting species such as dyer's greenweed (Genista tinctoria) and the marsh gentian (Gentiana pneumonanthe) thrive. Birds are well-represented too; spoonbills (Platalea leuco-rodia), hen harriers (Circus cyaneus), Montagu's harriers (C. pygargus), Kentish plovers (Charadrius alexan-drinus), black-tailed godwits (Limosa limosa), avocets (Recurvirostra avosetta) and eiders (Somateria mollissima) all breed. A number of passerines such as the marsh warbler (Acrocephalus palustris), golden oriole (Oriolus oriolus) and red-backed shrike (Lanius collurio) also breed.

[Photo: Lisette Pons]

332 The Wadden Sea's common seals (Phoca vitulina) are a single population. Seals are at the top of the food chain and therefore accumulate toxic pollutants, which reduce their fertility. They are thus an excellent indicator of seawater quality. PCBs were probably responsible for the 1988 viral epidemic that reduced the seal population by 60%. Nevertheless, aerial surveys carried out the following year revealed that there were around 4,500 seals still alive. The Wadden Sea is a stronghold for the European common seal population. Birth takes place in June on temporary sandbanks, or even in the water, and the pups are suckled in inaccessible places, far from human interference. The young seals can swim when they are born and any disturbance between May and September can have extremely negative effects on the long-term survival of the pups. The adults molt in September and during this month large groups can be seen on sandbanks. They feed mainly on fish, and in Dutch waters flounders form 30% of their diet, whiting 17%, and herrings another 17%. Younger seals may eat large quantities of prawns. Seals have no natural predators other than the occasional killer whale (Orcinus orca), although lung worm parasites are a common cause of death and probably a factor in controlling seal populations.

[Photo: George McCarthy / Bruce Coleman Limited]

333 The knot (Calidris canutus) is a medium-sized shorebird, representative of the migratory birds that stop over in the Wadden Sea. Around 850,000 knots, almost the whole world population, pass through the Wadden Sea on their way from their winter home in Africa to breed in the tundra of northeast Canada, Greenland and Siberia. When they arrive in the Wadden in April or May they have already molted from their gray winter plumage to their bright breeding attire with golden-speckled upperparts and a bright red breast. Some birds have flown so far that they arrive with their fat reserves exhausted. These gregarious birds reach the Wadden Sea in large flocks, remaining in them to feed or rest at high tide. They spend three or four weeks feeding on invertebrates and their body weight increases by 50%. When they leave, 2.5 oz (70 g) of their total body weight of 7 oz (210 g) is fat for use as energy reserves on the large journey ahead, enough to complete the second leg of their journey non-stop to Iceland. After a week there, they undertake the last stage to their breeding grounds in Greenland and Canada. Here they completely change their feeding habits to take advantage of the abundance of mosquitos and small insects on which they raise their young. Immediately after nesting, the females begin the return journey south and leave the males to care for the young until they too are able to start southwards. On the return journey, the knots arrive in the Wadden Sea between Au-gust and October and while some will continue to Africa, others spend the winter shuttling between estuaries in continental Europe and Britain.

[Photo: Jan van de Karn / Bruce Coleman Limited]

334 There is active fishing in the shallow waters of the Ijsselmeer, the inland sea protected by the Afsluit dike which lies between the Wadden Sea and dry land. Hoop nets, unusual in sea fishing, are employed.

[Photo: Phototheque Stone International]

335 Craft cheese production by local inhabitants using simple methods is an important economic activity in the Wadden Sea Biosphere Reserve.

[Photo: Xavier Ferrer]

336 Windmill and marshes are two of the most typical or representative features in the Wadden Sea Biosphere Reserve. Water and ancient human activity have given this area its most singular characteristics: the sea converted to dry land.

[Photo: Adolf de Sostoa & Xavier Ferrer]
COPYRIGHT 2000 COPYRIGHT 2009 Enciclopedia Catalana, SAU
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2000 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Publication:Encyclopedia of the Biosphere
Geographic Code:1USA
Date:Oct 1, 2000
Previous Article:Caviar.
Next Article:Bibliography.

Terms of use | Privacy policy | Copyright © 2021 Farlex, Inc. | Feedback | For webmasters |