BiodiversityBiodiversity or Biological Diversity, sum of all the different species of animals, plants, fungi, and microbial organisms living on Earth and the variety of habitats in which they live. Scientists estimate that upwards of 10 million—and some suggest more than 100 million—different species inhabit the Earth. Each species is adapted to its unique niche in the environment, from the peaks of mountains to the depths of deep-sea hydrothermal vents, and from polar ice caps to tropical rain forests..,
Biodiversity underlies everything from food production to medical research. Humans the world over use at least 40,000 species of plants and animals on a daily basis. Many people around the world still depend on wild species for some or all of their food, shelter, and clothing. All of our domesticated plants and animals came from wild-living ancestral species. Close to 40 percent of the pharmaceuticals used in the United States are either based on or synthesized from natural compounds found in plants, animals, or microorganisms.
Most biologists accept the estimate of American evolutionary biologist Edward O. Wilson that the Earth is losing approximately 27,000 species per year. This estimate is based primarily on the rate of disappearance of ecosystems, especially tropical forests and grasslands, and our knowledge of the species that live in such systems. We can measure the rate of loss of tropical rain forests, for example, by analyzing satellite photographs of continents from different periods that show rates and amounts of habitat destruction—and from these measurements calculate the approximate number of species being lost each year.The Biodiversity Issue: Is Nature At Risk?
Each spring vast flocks of songbirds migrate north from Mexico to the United States, but since the 1960s their numbers have fallen by up to 50 percent. Frog populations around the world have declined in recent years. The awe-inspiring California condor survives today only because of breeding programs in zoos. These are only a few of the species of life on Earth whose continued existence is in question; indeed, many scientists say that the Earth's biological diversity, or biodiversity, is growing more fragile with each passing year.
'Biodiversity' is a relatively new word. It encompasses not just individual species but the relationships between species and their habitats, whether that habitat be a few acres of rain forest or an entire ocean touching several continents. Increasingly, scientists are studying whether various habitats, and the species they harbor, can survive the massive changes that human beings have wrought on the planet, particularly in clearing forests and plains for agriculture and ranching. Harvard University biologist Edward O. Wilson, one of the leading authorities on biodiversity, estimates that the world could lose 20 percent of all existing species by the year 2020.
If present trends continue, these species will not fade into extinction one by one but in large groups, in what Wilson calls mass extinctions. There is evidence that such sweeping disappearances may already be occurring or may be about to occur. Half of the freshwater-fish species once found in peninsular Malaysia have become extinct, as have half of the 41 types of tree snails native to Oahu in the Hawaiian Islands. Of 68 varieties of shallow-water mussels once found along the shoals of the Tennessee River, 44 are thought to be extinct. And when just one ridge in Ecuador's rain forest was cleared, up to 90 plant species were wiped out. If the Earth is an ark carrying all living things, the British environmentalist Norman Myers has said, then it is a sinking ark.
Nations and conservation organizations are responding to such alarms with a wide variety of laws, programs, and techniques intended not just to keep individual species from becoming extinct but to defend unique ecosystems, especially the tropical rain forests, which support an abundance of life.
However, the issue is not without controversy; calls for restraining economic development or population growth in the name of saving biodiversity are sometimes branded alarmist or wrong-headed by critics.
Why Save Species?
But why go to the trouble of saving species and ecosystems? Countless species became extinct before humans evolved into the dominant form of life on Earth. Habitats and ecosystems changed dramatically. Indeed, several mass extinctions have taken place during the Earth's history (at least some of them, many scientists believe, were triggered by a catastrophic event such as a gigantic volcanic eruption or a collision of an asteroid or comet with the Earth). One estimate is that on average, before the advent of the human era, an ordinary century saw 25 species die off; meanwhile, new species appeared. Why should things be different now?
'It wouldn't be important from a human perspective if we weren't, in some senses, just another species on Earth,' says Forsyth. 'Ultimately, our physical well-being depends on maintaining the biodiversity of life.'
Plants provide oxygen, which we breathe, and they also help renew air tainted by industrial development. Plants and animals provide us with food and with fibers for clothing. One might object that species used by human beings for food and clothing are in no danger of extinction. In fact, their widespread cultivation in carefully controlled monocultures—areas such as farms where only one species is allowed to flourish—has pushed many other plant species to the very brink of extinction. Only 20 plant species provide the vast majority of the world's food. Of those, just four—wheat, rice, corn, and potatoes—feed more people than the next 26 crops combined.
But relying on just a few plant varieties as food sources may be shortsighted. Suppose a disease or pesticide-resistant insect devastated a food species. In that case we might be tempted to turn to one of the estimated 30,000 other varieties of plants that have edible parts, such as the remarkable winged bean plant of New Guinea. The entire plant, starting with its roots and including its seeds, leaves, flowers, and stems, is edible. Such a plant could be useful to human beings in the future, but only if it has not become extinct in the meantime.
Another reason to preserve the world's biodiversity is the vast potential for new medicines that can be formulated from compounds in plants. A recent example in the United States was the discovery that taxol, extracted from the Pacific yew tree, is effective in treating breast and ovarian cancer. The rosy periwinkle, an unprepossessing plant that originated in Madagascar, yields two substances, vinblastine and vincristine, that are useful in treating Hodgkin's disease and acute lymphocytic leukemia. The medicinal properties of plants are largely untapped; only about 5 percent of the estimated 250,000 species of trees, shrubs, and other plants have been studied for that purpose.
'The big logging companies considered the yew tree a trash tree,' says Gary Hartshorn, chief scientist at the World Wildlife Fund, an organization based in Washington, DC, that funds conservation projects around the globe. 'It used to be cut down and burned. If we had allowed all the Pacific old-growth forests to be cut down and go extinct, then we would not be able to save the lives of a lot of women who would otherwise die of cancer.'
Oxygen, food, clothing, and medicine are all important reasons to preserve biodiversity, but even so, the vast majority of the globe's known species have no practical value to humans. They simply exist. Whether that fact entitles an individual species to protection is a matter of sometimes heated debate—particularly when preserving biodiversity runs counter to the needs of human beings. If, say, an endangered tiger were killing people in a village, would the villagers be right to shoot the tiger? Or a less extreme but real situation: African elephants cause extensive damage to the landscape, including croplands, as they forage for food. Is it right to kill the elephants to save the crops for humans? Is it right even to prevent the elephants from moving through an area and thus limit their food supply?
But then there is the issue of the health and happiness of future generations. Ultimately, as Forsyth says, 'most people who are working to preserve biodiversity are doing it because they believe that the ultimate result of the current path of human development is self-destructive.'
Methods of Study..,
It is true that scientists do not have precise information about current extinction rates, but they try to make reasonable estimates. Based on experience around the world, biologists have developed a rule of thumb that if 90 percent of a habitat is destroyed, 50 percent of the species living in that habitat will become extinct.
Realizing that timeliness can be a critical factor in determining whether a habitat is bulldozed or saved, conservation biologists have also devised a variety of ways to assess an ecosystem quickly. Norman Myers and Conservation International have developed lists of 'hot spots,' areas of the world, particularly in the rain forests, that are especially rich in rare species that could be lost because of encroaching development. Conservation International has also established 'rapid assessment' teams for regions that are on the brink of being destroyed; these teams are groups of scientists who fly into an area to catalog quickly the varieties of plants and animals there in an attempt to show why a habitat should be saved.
Less crisis driven is a technique called gap analysis. In its simplest form, gap analysis involves overlaying a map of a species's known range on a map of preserved areas, such as national parks or nature preserves. That shows the difference, or gap, between a species's protected habitat and habitat that could someday be destroyed.
One of the governmental agencies that uses gap analysis is the U.S. Biological Survey, which was set up in 1993 to research the nation's biodiversity. Despite its name the organization is not in business to canvass all forms of life in the United States. Rather, it brings together scientists from seven different Interior Department agencies, with a special emphasis on providing an early warning before a species or ecosystem becomes endangered.
Even as it was being developed as an analytical tool in 1985, gap analysis proved useful. The U.S. Fish and Wildlife Service found that 90 percent of the habitat of such endangered Hawaiian forest birds as the Hawaii creeper and akepa was outside protected areas. The service, which was planning to establish a refuge for the birds, credits gap analysis with helping it choose a 15,480-acre (6,265-hectare) site that was home to more rare birds than the land it had been planning to purchase before the analysis was done. The site, the Hakalau Forest Wildlife Refuge, has since been increased by property purchases to 32,333 acres (13,085 hectares).
'Gap analysis gives you a target to shoot for,' says biologist J. Michael Scott, who works for the survey. 'But it also tells you where none of these species occur and where there won't be a conflict with development.'
Law in the Service of Nature..,
Gap analysis and other long-range techniques are meant to a serve a dual purpose—preserve biodiversity and avoid the kind of bitter disputes, such as a recent controversy over logging of old-growth forests in the U.S. Pacific Northwest, that Interior Secretary Bruce Babbitt has called 'national train wrecks.'
The collision in the Pacific Northwest centered on the fact that the forest is the habitat of the northern spotted owl, an endangered species protected under the premier U.S. conservation statute, the Endangered Species Act of 1973. The law established a procedure for categorizing scarce species as endangered or threatened (a less critical category) and gave regulators the power to restrict or prohibit activities, such as logging or construction, that threatened a species with extinction. The spotted owl dispute, for example, prompted both President Bill Clinton and Vice President Al Gore to attend negotiations between loggers and environmentalists in July 1993. The administration's compromise proposal, itself highly controversial, was completed in April 1994 and was greeted with legal challenges. In December, however, a federal judge approved the plan in a 70-page opinion that experts said left little possibility that the plan could be overturned by legal appeals.
Because it gives the U.S. government such broad powers, the Endangered Species Act has been criticized as being too restrictive, and several proposals are before Congress that would weaken the law. But supporters, such as the Environmental Defense Fund (EDF), respond by pointing out that in the vast majority of cases endangered status has not resulted in draconian limitations on property owners and developers. More important, the law has worked, they say. For instance, the California gray whale was taken off the list in June because its numbers had rebounded to about 21,000. Under the act it was illegal to kill or injure a gray whale or destroy its habitat. An even more notable success story has been the comeback of the species that symbolizes the United States—the bald eagle. Thirty years ago fewer than 420 breeding pairs were counted in the lower 48 states. Now that number has soared to more than 4,000 pairs. The EDF credits the Endangered Species Act with making it possible to protect the eagle's habitat, restore eagles to the wild, impose heavy fines for illegal killings, and ban lead shot and hazardous chemicals. As of November 1994, 761 animal species and 392 plant species were on the endangered list worldwide.
While the Endangered Species Act formed the legal locus of the logging controversy in the U.S. Pacific Northwest, a similar battle in Canada has centered on protest demonstrations carried out on the very land under dispute. At issue is the old-growth forest of the Clayoquot Sound region on Vancouver Island, British Columbia. In April 1993 a governmental decision to allow logging in about two-thirds of the area in dispute failed to satisfy environmentalists, who staged a series of bitter protests at logging sites. One August demonstration led to the largest mass arrest in the province's history. In 1994 the conflict continued. The government introduced such initiatives as a Forest Practices Code designed to ensure responsible logging, but protesters, notably the environmentalist organization Greenpeace, declared the code weak and unenforceable.
At the international level a key development was the Convention on Biodiversity, a treaty that came out of the 1992 'Earth Summit' in Rio de Janeiro. More than 150 countries signed the document, which made preservation of the world's biodiversity an international priority.
The United States did not sign at first, because the Bush administration argued, among other things, that the language of the treaty would force American companies to share research and patented processes for products made with natural resources from developing countries, such as wonder drugs. That also concerned the Clinton administration, which came into office in 1993, but a negotiating team resolved the issue by adding an 'interpretive statement' to the treaty that says corporations do not lose their proprietary rights in those cases. Madeleine Albright, the U.S. ambassador to the United Nations, signed the treaty in June 1994; late in the year it had yet to be ratified by the U.S. Senate.
Practical Steps..,
Some scientists believe that such agreements are not enough to halt the loss of biodiversity; a significant minority argue that maintaining biodiversity may require fundamental changes in the way humans live on and treat the Earth. But there are, nonetheless, small practical steps being taken today that offer hopeful signs for the survival of the globe's vulnerable species.
Paradoxically, it is the poorest nations, particularly nations along the equator, that are the globe's richest storehouses of natural diversity. Slowing the rate of habitat loss in such areas depends upon finding ways to encourage developing nations to view undeveloped land as an asset to be conserved for the future. One means is 'debt-for-nature' swaps, in which a developing country's national debt, payable in foreign currency, is swapped for domestic currency that is to be applied to conservation efforts. More than 15 nations had entered into such agreements as of fall 1994.
Another step for preventing habitat loss is to find economically valuable products in natural areas, be they Brazil nuts or chemical compounds for sophisticated biotechnology enterprises. In Costa Rica, where the remaining rain forests are limited to protected park areas, the government established a National Institute of Biodiversity, called INBio. Under a 1991 agreement with the U.S.-based pharmaceutical firm Merck, the organization provides Merck's drug screening program with chemical extracts from plants, insects, and microorganisms. Merck, in return, provides operating funds and royalties on products developed from the extracts. Several African nations have set up a similar institute headquartered in Zimbabwe.
Adopting less destructive techniques of logging is still another way to prevent habitat loss. The World Wildlife Fund's Hartshorn developed a new way of clear-cutting a rain forest called strip cutting, in which a long, narrow band of trees is logged. The strip is narrow enough that the forest can regenerate, yet logging companies still derive revenue from the land.
There are some signs that here and there the clearing of the tropical forests is slowing down. Indonesia, for example, a country that harbors a treasure trove of Asian plant and animal species, is shifting to more conservation-minded land-management practices.
And yet, despite all the attention that rain forests have received in the last decade, the amount of land that is logged annually remains fairly constant, about 15 million hectares (37 million acres). Hartshorn notes that as the rain forest dwindles, that amount represents an increasingly higher percentage of the remaining rain forest each year.
Hartshorn, for one, emphasizes that humanity is in a race to preserve biodiversity. Still, he sees reason for hope. 'We've got an increasing number of viable models for better, more sustainable ways to use natural resources,' he says. 'I'm cautiously optimistic about the future.'