Conserving biological diversity.

The incredible stew of genes, species, and ecosystems that both defines and sustains life on earth is deteriorating at a frightening rate. Here is a strategy for stemming the losses.

Biological diversity--complex beyond understanding and valuable beyond measure--is the total variety of life on earth. No one knows, even to the nearest order of magnitude, how many life forms humanity shares the planet with: Roughly 1.4 million species have been identified, but scientists now believe the total number is between 1O million and 80 million. Most of these are small animals, such as insects and mollusks, in little-explored environments such as the tropical forest canopy or the ocean floor. But nature retains its mystery in familiar places as well--even a handful of soil from the eastern United States is likely to contain many species unknown to science.

Despite the vast gaps in knowledge, it is clear that biodiversity--the ecosystems, species, and genes that together make life on earth both pleasant and possible--is collapsing at nothing less than mind-boggling rates. Difficult as it is to accept, mass extinction has already begun, and the world is irrevocably committed to many further losses. Harvard biologist Edward O. Wilson estimates that at a minimum, 50,000 invertebrate species per year--nearly 140 each day--are condemned to extinction by the destruction of their tropical rainforest habitat. Large creatures as well as small are vanishing: deforestation condemns at least one species of bird, mammal, or plant to extinction daily.

Moreover, biological impoverishment is occurring all over the globe. Ecosystems with fewer species than rainforests have, such as islands and freshwater lakes, are probably losing even greater proportions of their varied life forms. Genetic varieties within species and entire natural communities are also disappearing, likely at rates greater than the extinction of species themselves.

Protection of wildlands will be the top priority of any meaningful strategy to safeguard the world's biological heritage. True protection of these ecosystems alone will require sweeping changes in the way humanity views and uses land and a commitment to limit the amount of the earth's bounty that society appropriates to itself. But in order to staunch the massive bleeding of life from the planet, humanity must learn not only to save diversity in remote corners of the world but also to maintain and restore it in the forests and waters that we use, and in the villages and cities where we live.

Why should disappearing beetles, plants, or birds concern us? To biologists, and to many others, the question hardly needs asking: A species is the unique and irreplaceable product of millions of years of evolution, a thing of value for scientific study, for its beauty, and for itself. For many people, however, a more compelling reason to conserve biological diversity is likely to be pure self-interest: Like every species, ours is intimately dependent on others for its well-being.

Time after time, creatures thought useless or harmful are found to play crucial roles in natural systems. Predators driven to extinction no longer keep populations of rodents or insects in check; earthworms or termites killed by pesticides no longer aerate soils; mangroves cut for firewood no longer protect coastlines from erosion. Diversity is of fundamental importance to all ecosystems and all economies.

Life on the Brink

Biodiversity is commonly analyzed at three levels: the variety of communities and ecosystems within which organisms live and evolve, the variety of species, and the genetic variety within those species themselves. The degradation of whole ecosystems, such as forests, wetlands, and coastal waters, is in itself a major loss of biodiversity and the single most important factor behind the current mass extinction of species.

Home to at least half the planet's species, tropical forests have been reduced by nearly half their original area, and in 1990 deforestation claimed 17 million hectares (one hectare equals 2.471 acres), an area about the size of Washington state. In Benin, Cote d'Ivoire, Western Ecuador, El Salvador, Ghana, Haiti, Nigeria, and Togo, forests have all but disappeared. In most nations, forests occur increasingly in small fragments surrounded by degraded land, with their ability to sustain viable populations of wildlife and vital ecological processes impaired.

Brazil has more tropical forest--and likely more species--than any other nation. (See Table 1.) Massive deforestation continues there, but it has slowed appreciably since its 1987 peak, thanks to unusually rainy weather, changes in government policy, and a slowdown in the Brazilian economy. Moreover, with nearly 90 percent of its groves still standing, by national or international standards the Brazilian Amazon is relatively untouched. Brazil's most endangered ecosystems are its unique coastal forests. Logging and agricultural and urban expansion have destroyed more than 95 percent of the once-vast Atlantic coastal rainforests and the coniferous Araucaria forests of southern Brazil.

Outside the tropics, a number of ecosystem types have been all but eliminated from the planet, including the tallgrass prairies of North America, the great cedar groves of Lebanon, and the old-growth hardwood forests of Europe and North America. Less widespread than their tropical counterparts, temperate rainforests are probably the more endangered ecosystem. Of the 31 million hectares once found on earth, 56 percent have been logged or cleared. In the contiguous United States, less than 10 percent of old-growth rainforests survive, scattered in small fragments throughout the Pacific Northwest. In the rainforests of British Columbia, only one of 25 large coastal watersheds has wholly escaped logging.

Wetlands, like forests, are important repositories of biological diversity. Among the world's most productive ecosystems, they help regulate water flows, remove sediments and pollutants, and provide essential habitat for waterfowl, fish, and numerous other species. They are threatened in many parts of the world by drainage for agriculture or urban expansion, conversion to aquaculture ponds, overgrazing, and, in forested wetlands, logging.

Damage to wetlands has been severe in industrial nations, with losses in Australia, New Zealand, and California exceeding 90 percent. Canada houses one-fourth of the world's wetlands, and overall it has lost relatively few. But even here, major losses have occurred: Atlantic salt marshes, prairie wetlands, and Pacific estuarine marshes have all been reduced to a third of their original extent. Vast areas of bog and marsh remain in the country's sparsely populated northern regions.

The most familiar type of biodiversity loss is the decline of species, a process now occurring at thousands of times its natural "background" rate. (See Table 2.) The majority of species--and of extinctions--are invertebrates of the tropical forest too numerous to identify, let alone monitor the status of. Outside the tropics, the situation is somewhat easier to track. All 141 species of Hawaiian tree snail, for example, were listed as endangered by the U.S. government in 1981; today only two remain in substantial numbers, and they are declining rapidly.

Little attention has been paid to conservation of such unbecoming creatures, but their loss can have profound consequences. Populations of American oysters--once so numerous in the Chesapeake Bay that they filtered all its water every three days--have fallen by 99 percent since 1870. Now it takes a year for oysters to filter the waters of the Chesapeake, one reason the bay is increasingly muddied and oxygen-poor.

Reflecting the widespread degradation of aquatic habitats, freshwater fish are declining in many areas. In the main rivers and great seas (the Black, Caspian, Aral, and Azov) of the southern Soviet Union, more than 90 percent of major commercial fish species have been killed off. A recent four-year inventory in peninsular Malaysia found fewer than half the 266 fish species known to have inhabited the region's rivers before the advent of large-scale logging.

Intensive fishing has mined many coastal and open-ocean fisheries. Catches of Atlantic cod and herring, Southern African pilchard, Pacific Ocean perch, king crab, and Peruvian anchovies have all declined over the past two decades, according to the U.N. Environment Programme.

Scientists have discovered an apparent worldwide decline in amphibians (species such as frogs and salamanders) in recent years. Because amphibians divide their time between land and water habitats and their skin is permeable to airborne gases, they are especially sensitive indicators of environmental degradation.

Habitat conversion and acid precipitation are likely causes of many species, decline, but they mysteriously appear to be diminishing in seemingly pristine nature reserves.

Paralleling patterns of animal diversity, two-thirds of the world's plants are found in the tropics. Although prehistorical extinction spasms tended to claim mostly animals, plants are now threatened with extinction on a large scale. Peter Raven of the Missouri Botanical Garden estimates that one-fourth of all tropical plants are likely to be wiped out in the next 30 years.

Outside the tropics, the arid landscapes of southern Africa house the world's greatest concentration of threatened plants in the world. Four-fifths of the plants there are found nowhere else, and 13 percent of these--more than 2,300 species--are reportedly threatened.

About 3,000 species in the United States, nearly one in every eight native plants, are considered in danger of extinction; more than 700 are likely to disappear in the next 10 years without strong efforts to save them.

Genetic erosion is also a problem among wildlife forms: Through population reductions or intentional homogenization, many species have lost much of their internal diversity, and hence their ability to survive collectively.

On the west coast of North America, at least 106 major populations of salmon and steelhead have been wiped out; another 214 types of anadromous fish (those that migrate between freshwater and the ocean) are at some risk. Just as monoculture plantations have largely replaced the region's forest wilderness, hatchery fish have supplanted their wild cousins--about 75 percent of the Columbia River basin's fish are now hatchery-produced.

Protecting Ecosystems

For the past century, nature conservation efforts have focused on the protection of habitats in parks and other reserves. This strategy has had an important role in preserving biological diversity. Today there are just under 7,000 nationally protected areas in the world, covering some 651 million hectares, or about 4.9 percent of the earth's land surface. (See Table 3.)

Several nations have, on paper at least, set impressive proportions of their territory off-limits to development: Bhutan, Botswana, Czechoslovakia, Panama, and Venezuela notably have over 15 percent of their lands designated as parks. National or global figures, however, mask great unevenness. Parks in Chile, for example, are concentrated high in the scenic Andes, and more than half of Chile's unique vegetation types are not protected at all.

Globally, high-altitude habitats have received a disproportionate share of protective efforts, while others of greater biological significance (such as lowland forests, wetlands, and most aquatic ecosystems) have been neglected.

Today both modern and indigenous conservation systems are unraveling. In many areas, such as the Amazon basin, the often intimate knowledge of nature possessed by indigenous people is fading even faster than nature itself. On average, one Amazon tribe has disappeared each year since 1900. Especially for medicinal plants, traditional crops, and other life forms favored and used by native people, acculturation and the loss of traditional management systems are among the greatest threats to biological conservation.

The relationship between cultural diversity and biological diversity is more ambiguous in the case of large animal species. But the indigenous practices that do conserve wildlife are also vanishing as native cultures and territories succumb to the expanding influence of the global commercial economy. Orangutans, for example, have been virtually wiped out in the Malaysian state of Sarawak by destruction of their rainforest habitat and hunting. Only along the upper reaches of the Batang Ai River in southern Sarawak do they thrive, in part because local Iban people believe it is taboo to kill them. But the Iban, constantly told that their culture is backward, are abandoning their traditional beliefs, and orangutan hunting is reportedly on the increase.

Of the world's nationally protected areas, many, perhaps most, exist largely on paper. In the tropics, most parks have little or no staff or budget and are controlled by politically weak or corrupt departments. A 1988 survey by the Organization of American States found that only 16 out of 100 Caribbean marine parks (outside the United States) had management plans and adequate staff and funding.

The most common threats to parks originate outside their boundaries. Severe air pollution in Poland's Ojcow National Park has helped kill off 43 plant species there, and a third of the remaining plants are threatened. In just five years, explosives and cyanide used by local fishers have eliminated more than half the coral cover in the Philippines, Tubbataha Reef National Marine Park.

Over the past decade, many park managers have come to realize that the survival of protected areas depends ultimately on the support of local people, rather than on fences, fines, and even armed force. A number of promising projects have been initiated by governments and nongovernmental organizations to reduce pressures for exploitation by alleviating poverty in communities in or near protected wildlands. These projects have typically focused on establishing buffer zones around parks where limited exploitation of natural resources by local people is permitted; providing health care, water supplies, or other community services to compensate for lack of access to park resources; and supporting local economic development efforts such as tourism, wildlife ranching, or marketing of nontimber forest products.

The reasoning behind these efforts is sound: Poverty alleviation is the only feasible or ethically tenable means of protecting natural areas in the long term. But the difficulty of this approach should not be underestimated. Many villagers are rightly suspicious of parks departments, which, in their view, have stolen resources from them often not for protective purposes but for wealthier bureaucrats to exploit. Park managers typically find calls for more participatory management a threat to their authority. And by no means are all local people, indigenous or otherwise, interested in conservation of natural areas. Villagers on the outskirts of Khao Yai National Park in Thailand, for example, are among the staunchest supporters of a proposal to build a large dam in the park.

Given the great difficulties in protecting whole ecosystems, many have called for solutions less demanding than the defense of wilderness, defined as very large, roadless, lightly managed, minimally polluted ecosystems. Scientists have come to realize that change and disturbance--from fire and windstorms to the ancient practices of indigenous peoples--play important roles in fostering biological diversity. And foresters, among others, are beginning to design production systems aimed at mimicking these processes. In addition, it can be argued that there are no truly natural areas on the planet, since the impacts of indigenous people and industrial pollutants have been found in even the remotest territories.

So why maintain large areas with minimal human use? Quite simply, no other approach can protect biodiversity--at all its levels of organization--as well. Grizzly bear, harpy eagle, hornbill, spotted owl: Species that roam over large areas, that require specialized habitats, or that do not get along well with humans need large wilderness reserves if they are to survive outside of zoos.

Because disturbance is essential to natural ecosystems but often inconvenient to humans, large areas of wildlands are needed to let fires and other large-scale natural phenomena play their course uninterrupted. Also, for protected areas to be functional over the long term, they have to be ample enough to ensure that only a fraction of the area is involved in any given disturbance. Habitats too small to weather the impacts of random variation in weather and wildlife populations will not be able to maintain their full complement of genes, species, and functions. Where smaller parcels of habitat are all that remain, more active (and costly) management will be required.

In most nations, the opportunity to achieve a balance between wild and domesticated landscapes was lost long ago, and a necessary--if seemingly Draconian--goal is to cease "developing" any more relatively undamaged ecosystems. A first step toward this is determining where these areas are. In the United States, an Endangered Ecosystems Act has been proposed that would inventory and restrict development of any ecosystems reduced below a given percentage. On a global scale, Israeli landscape ecologist Ze'ev Naveh has proposed the compilation of a list of threatened landscapes.

Because so many remaining areas of global importance to biodiversity are inhabited by indigenous people, who usually have the greatest knowledge of the ecosystem to be safeguarded. protection will need to be on their terms. A first step is the recognition of the inalienable rights of people to lands and resources they have used for generations. In the Amazon basin, where native people have full legal title to less than 30 percent of their lands, the Venezuelan government broke with regional tradition in mid-1991 by recognizing an Austria-sized patch of forest as the permanent homeland of the beleaguered Yanomami tribe.

Conservation Beyond Parks

Even if societies undertake radical efforts to curb their impacts on remaining natural areas, most of the world's landscapes will continue to be dominated by human beings, and most will fall outside the scope of strictly protected reserves. Seminatural areas--such as second-growth forests, waters whose fish are intensively harvested, and rangelands grazed by livestock--prevail around the globe. Unless society can learn to tolerate and maintain wildness in these civilized landscapes, biodiversity has a bleak future.

Nature has long been viewed as an obstacle to economic development, and ecological decline seen as the inevitable price of progress. The protection of ecosystems within parks has usually been predicated on the assumption that natural systems outside them were to be homogenized at will. Recently, however, both environmentalists and industrialists have espoused the idea that economic and environmental well-being are linked, not opposed, and have begun to seek ways to blend production and protection.

Nonprofit groups and green-minded businesses are bringing new foods, cosmetics, medicines, soaps, and other products from the world's tropical forests to stores in Europe and North America. The range of products hidden in forests, reefs, and other ecosystems is a powerful argument for their conservation. Less than 1 percent of the plants of Madagascar, for example, where medicinal plants are a major export as well as the basis of local health care, have been analyzed chemically. But it is frequently overlooked that many species little known to science or industry are already used and managed by local communities.

Tropical forests are critical to hundreds of millions of rural people as sources of nutrition, health care, raw materials, and cash income. Traditional medicine, based largely on tropical plants, nurtures four-fifths of humanity, while rainforest plants provide key ingredients in pharmaceuticals worth tens of billions of dollars annually. International commerce in the most widely traded nontimber forest product, rattan (palm stems used for wicker furniture and baskets), is alone worth roughly $3 billion annually.

As with rangelands, fisheries, and wildlife throughout the developing world, forests have long been managed as common property resources, often with few negative ecological impacts. Many communal management systems are unraveling as populations surge, traditional cultures erode, and national governments confiscate or privatize resources held by communities. In addition, when subsistence-level economies have adopted modern technologies or become commercialized, increasing levels of production have tended to strain local ecosystems without improving local welfare.

From Southeast Asia's rattan to the fish and fruits of the Peruvian Amazon, the usual fate of species that gain long-term popularity in industrial markets is depletion. And the usual lot of their harvesters is continued poverty, as the profits from their work are siphoned off by powerful intermediaries and elites. Brazil nut gatherers, for example, receive about 4[cts.] a pound for their labors, just 2-3 percent of the New York wholesale price. Three-fourths of the market is controlled by three companies, owned by three cousins.

Rainforest trees form the base of a complex food chain. In turn, they rely on birds, insects, mammals, and even fish to disperse their pollen and seeds. According to ecologist Charles M. Peters of the New York Botanical Garden, "it is obvious that removing commercial quantities of fruits, nuts, and oil seeds will have an impact on local animal populations." The economic incentive to "enrich" forests with money-making species and cut down their competitors could also reduce the diversity of plant species (along with symbiotic animals) within extraction areas. Without careful management, losses at the genetic level are also likely: as the best fruits or leaves from a given population are continually harvested, the "inferior" plants may be the ones to survive over time.

The dangers of market-oriented extractive economies can be minimized by carefully choosing species and ecosystems. Some tropical forest areas are naturally less diverse than others and thick with commercially promising species--such as the vitamin C-rich fruit of the camu camu that grows in dense stands throughout the floodplains of the Peruvian Amazon. Ancient yet seminatural forests also hold great promise. Anthropologist Christine Padoch of the New York Botanical Garden reports finding fruit-filled, remarkably diverse groves (44 tree species within 0.2 hectares) in Kalimantan, Indonesia, that had been created by generations of villagers casually planting, weeding, and even spitting out fruit seeds over their shoulders.

In some cases, making the use of diversity rewarding to local people can be aided by developing markets for new or unknown products. But in all cases, this approach will work only if the fundamental concerns of the rural poor are addressed first. Political reforms will be required to secure rural people's rights to land and resources, reduce their vulnerability to exploitation and violence by outsiders, and ensure that the benefits of conservation stay within local communities.

Reconciling diversity with development will require loosening the grip of industry on natural resources and accepting that production of any single commodity will be constrained if ecosystems are managed for diversity. The success of some U.S. foresters' efforts to develop a "New Forestry," for example, depends on whether they can free forest management from its historical timber bias. Rather than homogenize ecosystems in order to maximize wood production, New Forestry ostensibly aims to maintain and use the ecological complexity of natural forests. But because diversity conservation will require protecting the few scattered remnants of pristine forest and logging other areas less intensively, New Forestry cannot succeed without major reductions in the timber harvest on national forests--a politically charged issue.

While New Forestry, extractive reserves, and other programs of sustainable commercial use of ecosystems are in their infancy, it is already clear that their success depends on programs of sustainable nonuse. Protecting large areas of undisturbed forest near logging or extraction areas is the only way to ensure the survival of animals that pollinate and disperse the seeds of commercially important tropical trees. Studies in the western United States have shown intact stands of native forest to harbor insect predators that safeguard plantations from pest outbreaks; the protection of coral reefs from fishing in Belize and the Philippines has revived local fishing economies by providing depleted fish stocks room to grow. Ultimately, only natural areas can tell us if our uses are in fact sustainable. As essayist Wendell Berry writes, "We cannot know what we are doing until we know what nature would be doing if we were doing nothing."

Living with Diversity

Fishers' nets and loggers' saws may directly impoverish local ecosystems, but most biological losses have root causes far away, in long-settled farmlands and urban areas where diversity is seldom a concern. In general, these peopled landscapes have lost much of their biological wealth, but what remains is still important to their continued functioning and livability. Reconciling farms and cities with diversity will require stopping the damage they bring to remaining natural habitats, but also beginning to halt and reverse the homogenization of these unnatural environments.

Urban areas, with good reason, are considered the antithesis of natural diversity. Only the most resilient creatures--those considered weeds and pests--thrive in them, and cities, ceaseless expansion, consumption of resources, and emissions of waste threaten both farmland and wilderness almost everywhere. As with agricultural lands, the first priority for urban areas is to halt their expansion onto other ecosystems and reduce the damage they export, such as the sewage poured onto coral reefs by burgeoning coastal cities throughout the tropics.

But even concrete jungles can support some diversity. Most urban areas have waterways running through them or corridors of unused land such as steep ravines; if their use as waste receptacles is reduced, these can be maintained or restored as wildlife habitat. A number of European and U.S. cities have moved to establish greenway corridors along rivers, old railroad tracks, and urban perimeters. Although, created primarily for recreation, these greenways have great biological potential to help reconnect increasingly fragmented and dysfunctional enclaves of nature beyond city limits.

Especially in developing nations, a surprising amount of agricultural production takes place within city limits, in home gardens. These hidden farmlands contain a great deal of genetic diversity and their expansion could help reduce the environmental impacts of commercial agriculture. In the United States, converting a quarter of the 13 million hectares of lawn to gardens would be equivalent to expanding the nation's cropland by 2 percent.

One of the reasons biological diversity is so threatened is that urban dwellers have little experience of the natural and less understanding of its importance. Restoring nature where people live--re-establishing a personal link with the living world--is necessary if we are to save it.

Infusing the world's peopled landscapes with wildness assumes even greater importance in the face of the ultimate threat to life on earth: global warming. In countless ways, a rapidly warming world will be hostile to life. Most notably, natural communities will be forced to migrate away from the equator, or up from sea level, if they are to maintain their usual climate. Even if reduced emissions of greenhouse gases slow global warming to a pace that migrating ecosystems can keep up with, habitats fragmented by roads, clearings, and human settlements will literally be pushed up against the wall. Only by making diversity a concern on all landscapes, from the wild to the urban, can the inevitable migrations of species and communities be accommodated, and the options to deal with unpredictable change be maintained.

Ironically, the most important reforms are those that seemingly have little to do with biodiversity. To intelligently limit the amount of the planet we dominate and to tolerate nature more in the places we do dominate will entail tackling two of the most intractable and fundamental forces in the modern world: galloping consumption and exponential population growth. No conservation strategy, however ingenious, can get around the fact that the more resources one species consumes, the fewer are available for all the rest.

Many of the changes needed for biodiversity's sake are a step beyond those considered in discussions of sustainable development. The human costs of a lost medicinal plant may never be known, and any economic deterioration that results from biological decline could take years or decades to appear. But the protection of biodiversity has to be considered a basic requirement of sustainability--passing on to future generations a world of undiminished options--and a fundamental moral responsibility as travelers on the only planet known to support life.

John Ryan is a research associate at Worldwatch Institute and a co-author of the book State of the World 1992, from which this article is excerpted. The book is available from Worldwatch Institute, 1776 Massachusetts Ave. NW, Washington, DC 20036. Price is $10.95 for paperback, $19.95 for hardcover.