According to the 1995 Global Biodiversity Assessment by the United Nations Environment Programme (UNEP), humans share the planet with an estimated 13 million other species. A generation ago, that estimate was 1.3 million, but more species are discovered every year, and human activities drive more species to extinction every day. Many of these organisms, and the larger communities they represent, provide us with medicine, food, recreation, environmental stability, and other vital commodities and services. About 90% of the world's species, mostly insects and fungi, have not yet been studied or even given scientific names.
The 1,100-page UNEP report, developed with the help of more than 1,500 scientists, is a volume that is perhaps more discussed than read by policymakers and environmentalists alike. Although the public tends to equate the biodiversity issue with endangered species protection, UNEP makes it clear that biodiversity, or biological diversity, covers a broad spectrum of measurements and classifications. It encompasses alpha diversity, or species richness (the number of species in an area); species diversity (an index of proportions as well as numbers); and several complex measures of ecological, taxonomic, and genetic diversity within and between species. An ecosystem is more than the sum of its species.
The Numbers Game
The stated goal of the U.S. Endangered Species Act (ESA)--hailed by some as a model for the world and reviled by others as hopelessly flawed--is ecosystem conservation. In practice, however, the ESA has focused largely on one aspect of biodiversity: species richness. A species facing imminent extinction is placed on a list and becomes the target of often heroic protection measures, regardless of that species' long-term viability or ecological role. In many cases, endangered species protection involves some level of interference with private rights and interests. As the list grows longer, tempers among proponents and opponents alike grow shorter. And biodiversity continues to decline, for numbers alone do not tell the whole story.
The debate surrounding the ESA, and the larger issue of biodiversity protection, often overlooks the fact that an ecosystem can change drastically without losing a single species. For example, overfishing has not driven a single marine fish species to extinction, yet it has changed the balance of ocean communities and deprived many people of particular seafoods. Another example is an old swimming hole in a small town that is supplied by polluted runoff and an aquifer underlying a dairy farm. Instead of admiring the tadpoles, freshwater clams, and dragonflies that once flourished there, visitors now experience mats of decomposing algae populated by fly larvae that eat bacteria and organic wastes. The former occupants are rare but not extinct (though rare species are more likely to become extinct); species richness is the same, yet species diversity and aesthetic values have plummeted.
On a larger scale, forest structure in California's Sierra Nevada is dramatically simpler today than it was a century ago. Fire suppression, intended to save the forest, is now recognized as a major cause of its deterioration. Exotic species introduction is another cause. "Amphibians are the most severely affected," reports Constance Millar, co-founder of the Center for the Conservation of Genetic Diversity. According to Millar, the introduction of game fish has decimated native frog populations. The total numbers of species may be the same, but the diversity has declined. The most obvious measures to restore biodiversity would include the removal of sport fish from popular fishing areas and drastic curtailment of firefighting efforts. In such cases, however, when biodiversity protection is inconsistent with more immediate human needs, policymakers often choose the latter.
Aside from its lack of focus on ecosystem structure and function, the ESA necessarily excludes the most important groups of all: the microscopic algae that support marine food webs and generate oxygen, and the bacteria and fungi on which nutrient cycles and crops--and therefore human lives--depend. No agency could monitor such species individually. But this fragmented approach, while a laudable first step toward preserving the Earth's genetic library, does little to protect the ecosystem values with the most immediate relevance to humans. "Most of the reports are done by bean-counters," says Stephen Hubbell, a professor of ecology and evolutionary biology at Princeton University. "They're making policy decisions based on an inadequate database about ecosystem structure or function."
Human Impacts on Biodiversity
Although species formation and extinction are ongoing processes, extinctions in recent decades have occurred at about 1,000 times the estimated background rate. Many scientists believe that we are experiencing a mass extinction, the latest of several. Not all authorities hold humans solely responsible for this trend: life has survived previous catastrophes, and it will probably survive human existence. And some argue that the ways in which humans are transforming ecosystems may create opportunities for future biodiversity. But the restoration of species diversity will take millions of years, and the UNEP report cites human activity as the largest threat to species extinction.
Threats to biodiversity include the destruction and fragmentation of habitat; harvesting of wild species for food, lumber, and other products; introduction of non-native animals and plants; pollution of the air, water, and soil with toxic chemicals and waste products; and increased ultraviolet radiation and global warming resulting from atmospheric effects of human activities. These are the immediate causes of biodiversity loss. Underlying these processes, however, are forces far less amenable to government regulation: unrestrained human population growth, failure to recognize the economic value of biodiversity, and a host of competing and conflicting environmental stewardship concepts.
Preservation. Proponents of preservation seek to halt the decline of biodiversity, regardless of circumstance or cost. For example, the ESA protects endangered species even if the threats to their existence are natural. Many biologists object to this goal of "freezing" ecosystems at a designated point in time.
Conservation. This philosophy, popularized by President Theodore Roosevelt, maintains that humans need biodiversity and should take reasonable steps to limit its consumption. The difficulty lies in defining the boundaries of what is reasonable and economically feasible.
Custody. The viewpoint that humans are responsible for nurturing other species and deciding their fate has fueled the recent Christian environmentalist movement, exemplified by Calvin DeWitt of the Evangelical Environmental Network: "Imaging God, we too should provide for the creatures." In contrast, paleontologist Stephen Jay Gould of Harvard University warns humanity that "We are one among millions of species, stewards of nothing."
Dominion. Yet another view is that all natural resources are the property of humanity, and that government has no right to restrict their use. This sentiment is shared by a growing number of Americans who are frustrated not only with the ESA, but with government regulation in general. Bob Shattuck, director of governmental affairs for the Building Industry Association, says, "We just don't feel they should be able to take away our property without giving any reason."
These issues have generated a variety of proposals for amending the ESA. Legislators now face the daunting task of making decisions with possible long-term environmental consequences and impacts to human health and quality of life.
Human Health Implications
Many factors that reduce biodiversity, such as air pollution and increased ultraviolet radiation, also affect human health. Only recently has the idea that biodiversity loss itself is a public health concern gained wide acceptance. The best-known example is the loss of potential medicines from plants and other organisms. Most of the commonly prescribed drugs in the United States were originally derived from plants or fungi. One source estimates that one in 125 plant species contains a useful pharmaceutical. UNEP and other sources predict that 3% of the world's 300,000 plant species may become extinct in the next 25 years. The resulting loss of drugs would mean an economic price tag of hundreds of millions of dollars, and an inestimable cost in human lives and suffering. "We are rapidly losing indigenous medicinal knowledge," says Gretchen Daily, a research scientist at Stanford University.
Nor are plants and fungi the only potential drug sources in nature, as shown by the recent discovery of a beetle that produces cortisone. Had this source been recognized prior to the synthesis of cortisone in 1951, it could have saved many lives. Frogs and salamanders, whose numbers are dwindling worldwide for unknown reasons, are the source of several neurotoxins used in medical research. And venomous snakes have yielded life-saving anticoagulant drugs. The urgency of discovering new pharmaceuticals and preserving their sources is compounded by the recent emergence of "new" diseases such as AIDS and Lyme disease, and viruses such as Ebola, as well as drug-resistant strains of old ones such as tuberculosis, Staphylococcus infections, and syphilis.
Biological prospecting has its critics. The 1-in-125 estimate of plant sources disregards the fact that closely related species may contain the same compounds. Also, prospecting itself can reduce biodiversity; the unsustainable exploitation of yew trees for production of taxol is no better than overfishing. An extreme example, cited in the UNEP report, occurred when the National Cancer Institute harvested the entire known adult population of a shrub that contains the anticancer compound maytansine. There is also the issue of international cooperation and equitable sharing of profits. Congress has yet to ratify the 1992 Convention on Biological Diversity--a global treaty that promotes biodiversity protection that was prepared under the auspices of UNEP, presented at the 1992 Earth Summit, and signed by President Clinton in 1993. Unless ratification occurs soon, the United States could be blocked from biological prospecting in developing countries.
Besides depriving us of medicines, biodiversity loss can actually create disease epidemics. Disturbed ecosystems often have lower species diversity than natural ones, with fewer checks and balances to prevent outbreaks. An example is the recent emergence of hantavirus pulmonary syndrome in the American Southwest. The agent is not new; hantavirus is endemic in deer mice, but does not make them sick. When the mouse population density rises sharply, the incidence of hantavirus infection increases, and transmission to humans becomes more likely. The recent outbreaks apparently were triggered by the loss of predators, due to human encroachment that had kept the rodents under control. Agriculture, waste disposal, and other human practices also promote surges in rodent populations.
Another disease that may be related to biodiversity is shellfish poisoning, a severe illness that results when humans eat seafood containing neurotoxins produced by certain dinoflagellates and other marine algae. Massive outbreaks of such algae, often called red tides, are increasing worldwide. When pollutants are introduced to coastal waters, shifts in nutrient ratios can favor toxic blooms. Dinoflagellates also invade damaged coral reefs, and the ability of many harmful algae to form protective cysts may favor their survival and proliferation under disturbed conditions. Although the causes of red tides are not fully understood, all these scenarios involve changes in ecosystem structure. "The amount of reorganization we have done in the ocean is monumental," says Carl Safina, director of the Audubon Society's Living Oceans Program.
The ultimate example of a disturbed, simplified ecosystem community is bare ground. Dirt roads, construction sites, overgrazed pastures, poorly managed farmland, and desert land damaged by off-road vehicles all generate dust that contributes to air pollution and associated illness. These trends recently caught up with California's Coachella Valley, once a haven for those with respiratory diseases. In 1992, the South Coast Air Quality Management District designated the valley as a serious non-attainment area for air quality standards due to manmade sources of fine dust.
Quality of Life
Health, in the most basic sense, means more than the absence of disease. Biodiversity is essential to other aspects of health, such as food, recreation, and employment. Overfishing, for example, affects food supplies and economics; a well-known example is the depletion of the North Atlantic herring population and its domino depleting effect on Arctic cod, seabirds, harp seals, and other organisms. Recently, however, more attention has been focused on less obvious consequences of decreased biodiversity. The wild relatives of modern-day crop plants and livestock are a case in point.
High-yield varieties of crops such as corn and potatoes are nearly uniform genetically; as a result, they are highly vulnerable to pests, pathogens, and climate changes. Hybridization with wild strains, preserved as wild populations or in gene banks, holds the most promising solution in many cases. The introduction of new genes also can enhance nutritional value. According to the U.S. Department of Agriculture, at least 37 of the 250 plant species now listed as endangered or threatened carry genes with commercial value. If these species become extinct, their genetic potential will be lost forever. A recent survey by the Center for Plant Conservation in St. Louis, Missouri, showed that the loss of rare plant species represents a substantial economic threat to the United States.
Some health effects are harder to quantify. The effects of natural landscapes on mental health is addressed in a forthcoming book, Biodiversity and Human Health (Island Press, October 1996), edited by Francesca Grifo, director of the Center for Biodiversity and Conservation, and Joshua Rosenthal, acting manager of biodiversity programs at the Fogarty International Center. Recreation, in the form of hunting, fishing, hiking, and scuba diving provides respite to millions--yet these activities, too, are feeling the effects of biodiversity loss.
To hunters who ask what the extinction of the ivory-billed woodpecker can possibly mean to them, the answer is clear: it isn't just the woodpecker we have lost, it's the forests they once lived in. Describing the primordial forests of the southeastern United States in 1773, explorer William Bartram worried that no one would believe his report of trees 10 feet in diameter. Today these forests are gone, replaced by easily managed plantations of fast-growing pines. Nor can divers and snorklers escape these trends. The UNEP report estimates that 70% of coral reefs worldwide will be destroyed or severely damaged within the next 40 years.
Employment, a source of self-esteem as well as economic sustenance, is also at stake. In coastal waters throughout the world, traditional fishermen have fallen on hard times. Loggers in the Pacific Northwest, in similar circumstances, were betrayed not by the spotted owl, but by unwise resource management.
The Unknown
Of the 1.75 million species described to date, few have received more than cursory study because their roles in the ecosystem are so poorly understood; the consequences of their loss are largely unpredictable. For example, in rural areas that depend on underground septic tanks for sanitation, tiny insects called springtails play a key role in keeping the filter gravel working. Where pesticides kill these insects, groundwater pollution could theoretically increase. In addition, who could have anticipated that the study of a heat-loving bacterium found in hot springs would inspire the use of the polymerase chain reaction as a fundamental tool of biotechnology, or that certain mustard plants could bioconcentrate heavy metals, thus removing them from contaminated soil?
Many organisms also serve as environmental sentinels, warning of threats to human health. Biologists recently reported that some male alligators in Florida have smaller-than-usual penises and are unable to reproduce, possibly from exposure to environmental estrogens. There is evidence that the same pesticide residues that can ruin an alligator's social life may explain the worldwide decline of human male sperm counts and rising breast cancers in women. The UNEP report cites Paul Ehrlich's "rivet analysis," which states that removing species randomly from an ecosystem is like popping rivets from an airplane's wing. The wing begins with more rivets than it needs, but at some point the structure will fail.
Although few scientists would disagree with the general premise that biological diversity is declining, there is no consensus regarding the severity or consequences of this trend. Some dispute the numbers, claiming that recent extinctions are nothing more than a blip on the great cosmic curve. Many believe that the very presence of a large human population makes biodiversity loss inevitable. Others note that few organisms qualify as "keystone species," with major roles either in their ecosystems or in human lives. For example, no industry will mourn the loss of the Delhi Sands flower-loving fly.
There is also a growing suspicion that biodiversity protection measures may be based on faulty assumptions. For example, the Lithuanian Nature Fund recently reported that an abandoned Soviet military base, highly contaminated by most standards, shows exceptionally high biodiversity. The base has even served as a refuge for bird and mammal species that are rare elsewhere in Lithuania. It is possible that simply excluding people from an area is more effective than the most elaborate wildlife management program. Other data challenge the axiom that people instinctively love nature. Mark Sagoff, in The Economy of Earth, tells how his students reacted to the hypothetical development of a ski resort in a wilderness area. Although the students said the wilderness should be protected, they had no interest in going there; they preferred the resort. If enough people lose interest in environmental protection, ultimately the laws will reflect this.
The ESA, the only federal law in the United States that addresses biodiversity, expired in 1992 and had not been reauthorized at the time of this writing. Several bills in the 104th Congress propose major changes to the ESA. Perhaps the most controversial are HR 2275 (Young-Pombo) and S 1364 (Kempthorne). Both offer compensation to landowners if federal action reduces their property value, and require better scientific justification for listing species. HR 2275 also includes tax incentives to property owners for habitat conservation planning. These measures have been well received by many, but even their supporters sometimes fail to notice that both bills also remove the protection of endangered species habitat. This fact is a major sticking point. "The real problem is in compensating private property owners when they can't use their land," says Supervisor Mary K. Shell of Kern County, California. Shell, who supports HR 2275 on this basis, feels that the law should protect both species and their habitat. In contrast, Dan Ashe, assistant director of the U.S. Fish and Wildlife Service, believes ESA opponents invent "horror stories." In most cases, Ashe points out, ESA compliance is about as inconvenient and expensive as getting a sewer permit. Yet few Americans claim the right to dump raw sewage on the street.
At last count, 142 nations had ratified the Convention on Biological Diversity. Related measures in many countries, notably Australia and the Netherlands, include comprehensive environmental management programs and strategies for ecologically sustainable development. The inaugural Asia-Europe Meeting (ASEM) in Bangkok in March reiterated the importance of biodiversity management. The convention and related international agreements, however, contain few specific requirements for action, focusing instead on research and planning. In the United States, Senate approval of the convention has been delayed by concerns about possible effects on industry. It remains to be seen if these measures will resolve key issues of international cooperation and achieve the goal of long-term biodiversity conservation.
Joan R. Callahan
Last Update: May 22, 1997