Only Humans Can Halt the Worst Wave
of Extinction Since the Dinosaurs Died

by E.O. Wilson

Edward O. Wilson, a leading advocate of global conservation, is Pellegrino University Professor at Harvard. His book The Diversity of Life will soon be available in 14 languages around the world.

The Baiji is a graceful, freshwater dolphin that once abounded along a thousand miles of the Yangtze River. It may now be the world's most endangered large animal. Caught in a vise of rising pollution and indiscriminate fishing during the past century, its population fell to only 400 by 1980, to 150 in 1993, and is now below 100. Zoologists doubt the species will survive in the wild for another decade. The baiji's closest rivals for early extinction include the Sumatran rhinoceros (probably fewer than 500 individuals survive) and the giant panda of China (fewer than 1,000).

The media can be counted on to take note when the last member of each of these species dies, or, like the California condor, is removed from the wild to be placed in a captive breeding program. But for every animal celebrity that vanishes, biologists can point to thousands of species of plants and smaller animals either recently extinct or on the brink. The rarest bird in the world is Spix's macaw, down to one or possibly two individuals in the palm and river-edge forests of central Brazil. The rarest plant is Cooke's koki'o of Hawaii, a small tree with profuse orange-red flowers that once graced the dry volcanic slopes of Molokai. Today it exists only as a few half plants--branches implanted onto the stocks of other related species. Cooke's koki'o may spend its last days in this biological limbo; despite the best efforts of horticulturists to assist the plant, no branches planted in soil have sprouted roots.

Around the world, biodiversity, defined as the full variety of life from genes to species to ecosystems, is in trouble. Responding to the problem, conservation experts have in the past two decades shifted their focus from individual species to entire threatened habitats, whose destruction would cause the extinction of many species. Such "hot spots" in the U.S., for example, include the coastal sage of Southern California, the sandy uplands of Florida, and the dammed and polluted river systems of Alabama and other Southern states. Arguably the countries with the most hot spots in the world are Ecuador, Madagascar and the Philippines. Each has lost two-thirds or more of its biologically rich rain forest, and the remainder is under widespread assault. The logic of the experts is simple: by concentrating conservation efforts on such areas, the largest amount of biodiversity can be saved at the lowest economic cost. And if the effort is part of the political process during regional planning, the rescue of biodiversity can gain the widest possible public support.

In hot spots around the globe, mass extinctions of local populations have been commonplace. Among them:

More than half the 266 species of exclusively freshwater fishes in peninsular Malaysia.

Fifteen of the 18 unique fishes of Lake Lanao in the Philippines, and half the 14 birds of the Philippine Island of Cebu.

All of the 11 native tree-snail species of Moorea in the Society Islands. Those on nearby Tahiti, as well as in the Hawaiian Islands, are rapidly disappearing.

More than 90 plant species growing on a single mountain ridge in Ecuador, through clear-cutting of forest between 1978 and 1986.

These well-documented cases notwithstanding, it is notoriously difficult to estimate the overall rate of extinction. Some groups, like the larger birds and mammals, are more susceptible to extinction than most. The same is true of fishes limited to one or two freshwater streams. Most kinds of insects and small organisms are so difficult to monitor as to make exact numbers unattainable. Nevertheless, biologists using several indirect methods of analysis generally agree that on the land at least and on a worldwide basis, species are vanishing 100 times faster than before the arrival of Homo sapiens.

Tropical rain forests are the site of most of the known damage. Although they cover only 6% of the land surface, they contain more than half the species of plants and animals of the entire world. The rate of clearing and burning of rain forests averaged about 1% each year in the 1980s, an amount about equal to the entire country of Ireland, and the pace of destruction may now be increasing. That magnitude of habitat loss spells trouble for the planet's reservoir of biodiversity. It means that each year 0.25% or more of the forest species are being doomed to immediate or early extinction. How much is that in absolute numbers, as opposed to rate? If there are 10 million species in the still mostly unexplored forests, which some scientists think possible, the annual loss is in the tens of thousands. Even if there are a "mere" 1 million species, the loss is still in the thousands.

These projections are based on the known relationships between the area of a given natural habitat and the number of species able to live within it. The projections may be on the low side. The outright elimination of habitat is the leading cause of extinction. But the introduction of aggressive exotic species and the diseases they carry follow close behind in destructiveness, along with overhunting or overharvesting of plants and animals.

All these factors work together in a complex manner. When asked which ones caused the extinction of any particular species, biologists are likely to give the Murder on the Orient Express answer: they all did it. A common sequence in tropical countries starts with the building of roads into wilderness, such as those cut across Brazil's Amazonian state of Rondonia during the 1970s and '80s. Land-seeking settlers pour in, clear the rain forest on both sides of the road, pollute the streams, introduce alien plants and animals and hunt wildlife for extra food. Many native species become rare, and some disappear entirely.

The world's fauna and flora are paying the price of humanity's population growth. The levy may be acceptable to those who put immediate human concerns above all else. But it should be borne in mind that we are destroying part of the Creation, thereby depriving all future generations of what we ourselves were bequeathed. The ongoing loss in biodiversity is the greatest since the end of the Mesozoic era 65 million years ago. At that time, by current scientific consensus, the impact of one or more giant meteorites darkened the atmosphere, altered much of earth's climate and extinguished the dinosaurs. Thus began the next stage of evolution, the Cenozoic era or Age of Mammals. The extinction spasm we are now inflicting can be moderated if we choose. If not, the next century will see the closing of the Cenozoic era and the start of a new one characterized by biological impoverishment. It might appropriately be called the Eremozoic era, the Age of Loneliness.

People commonly respond to the evidence of species extinction by entering three successive stages of denial. The first is, simply, Why worry? Extinction is natural. Species have been dying out through more than 3 billion years of history without permanent harm to the biosphere. Evolution has always replaced extinct species with new ones.

All these statements are true, but with a terrible twist. After the Mesozoic spasm, and after each of the four greatest previous spasms spaced over 400 million years, evolution required about 10 million years to restore the predisaster levels of diversity. Faced with a waiting time that long, and aware that we inflicted so much damage in a single lifetime, our descendants are going to be--how best to say it?--peeved with us. Worse, evolution cannot perform as in previous ages if natural environments have been crowded out by artificial ones.

Entering the second stage of denial, people ask, Why do we need so many species anyway? Why care, especially since the vast majority are bugs, weeds and fungi? It is easy to dismiss the creepy crawlies of the world, forgetting that less than a century ago, before the rise of the modern conservation movement, native birds and mammals around the world were treated with the same callous indifference. Now the value of the little things in the natural world has become compellingly clear. Recent experimental studies on whole ecosystems support what ecologists have long suspected: the more species living in an ecosystem, the higher its productivity and the greater its ability to withstand drought and other kinds of environmental stress. Since we depend on functioning ecosystems to cleanse our water, enrich our soil and create the very air we breathe, biodiversity is clearly not something to discard carelessly.

In addition to creating a habitable environment, wild species are the source of products that help sustain our lives. Not the least of these amenities are pharmaceuticals. More than 40% of all prescriptions dispensed by pharmacies in the U.S. are substances originally extracted from plants, animals, fungi and microorganisms. Aspirin, for example, the most widely used medicine in the world, was derived from salicylic acid, which in turn was discovered in a species of meadowsweet.

Only a minute fraction of the species or organisms--probably less than 1%--have been examined for natural products that might serve as medicines. There is a critical need to press the search in the case of antibiotics and antimalarial agents. The substances most commonly used today are growing less effective as the disease organisms acquire genetic resistance to the drugs. The bacterium staphylococcus, for example, has recently re-emerged as a potentially lethal pathogen, and the microorganism that causes pneumonia is growing steadily more dangerous. The age of antibiotics, it has been said, is over. Not quite, but medical researchers are nevertheless locked in an arms race with the rapidly evolving pathogens that is certain to grow more serious. They are obliged to turn to a broader array of wild species to discover the new weapons of 21st century medicine.

Each species is a masterpiece of evolution, offering a vast source of useful scientific knowledge because it is so thoroughly adapted to the environment in which it lives. Species alive today are thousands to millions of years old. Their genes, having been tested by adversity over so many generations, engineer a staggeringly complex array of biochemical devices to aid the survival and reproduction of the organisms carrying them.

Even when that much is granted, the third stage of denial usually emerges: Why rush to save all the species right now? We have more important things to do. Why not keep live specimens in zoos and botanical gardens--on ice, so to speak--and return them to the wild later? The grim truth is that all the zoos in the world today can sustain a maximum of only 2,000 species of mammals, birds, reptiles and amphibians, out of about 24,000 known to exist. The world's botanical gardens would be even more overwhelmed by the quarter-million plant species. These refuges are invaluable in helping to save a few endangered species. So is freezing embryos in liquid nitrogen. But such measures cannot come close to solving the problem as a whole. To add to the difficulty, no one has devised a plan to save the legion of insects, fungi and other ecologically vital small organisms. And once scientists are ready to return species to independence, the ecosystems in which many lived will no longer exist. Tigers and rhinos, to make the point clear, cannot survive in paddies.

The conclusion of scientists and conservationists is therefore virtually unanimous: the only way to save wild species is to maintain them in their original habitats. Considering how rapidly such habitats are shrinking, even that straightforward solution will be a daunting task. Many ecosystems have already been lost, and others seem doomed.

In spite of all these difficulties, there is reason for some optimism. With appropriate measures and the will to use them, the hemorrhaging can be slowed, perhaps eventually halted, and most of the surviving species saved. Some of the most important immediate steps that can be taken are outlined in the Convention on Biological Diversity, signed by 156 nations and the European Union at the 1992 Earth Summit in Rio de Janeiro (with its Senate hesitating to ratify, the U.S. is one of the few nations not yet a formal party to the agreement). The convention was the turning point in the awareness of biodiversity as a world issue. It served as a catalyst in accelerating conservation efforts and has been especially important in awakening tropical countries, where biodiversity is both the richest and most threatened.

One of the first moves under way is the closer surveying of biodiversity, country by country, to pinpoint the extinction hot spots. Such information, when used to sequester parks and reserves, can lead to the rescue of large numbers of endangered ecosystems and species. A review of bird distribution by the International Council for Bird Preservation, using the best data available for any group of organisms, revealed that 20% of the world's species occur within 2% of the land area. Protecting natural environments in these localities alone would help greatly to slow the rate of bird extinction. It would also shield larger numbers of other animals and plants limited to the same habitat.

Saving the last remnants of the natural environment requires more than just scientific information. There are also formidable economic and political problems to be overcome. Growing populations need new land and increased food production. The priorities of the desperately poor do not include saving the fauna and flora of their country. Funds must be raised to purchase much of the land from private owners, and then to pay for the protection and management of the reserves. To gain the support of local peoples, educational programs are needed to convey the importance of wild lands to sustaining their own environment in a healthy state. The poor need to be helped to a better life on the land they already occupy.

Out of this welter of conflicting interests has arisen a new kind of environmentalism. It values the world's fauna and flora not just aesthetically as the natural heritage of humanity but also as a source of wealth and economic stability. An infant biodiversity industry is now taking shape along several fronts. More than 20 pharmaceutical companies have contracted with private and national research organizations to push "chemical prospecting" for new medicines in rain forests and other habitats.

Ecotourism, opening the most spectacular wild lands to paying visitors, has become a major source of income in many developing countries. Reserves and the surrounding land are being reorganized to create an outer buffer zone where local peoples are helped to develop sustainable agriculture, enveloping an inviolate core zone for the maximum protection of endangered species. Some forest tracts previously scheduled for clear-cutting are now selectively logged or cut along concentric swaths, then allowed to regenerate. Because the practices yield higher long-term profits, they are expected to be widely adopted.

The new approach to biodiversity, uniting conservation and economic development, is obviously far from perfect, and it is not yet fully practiced in any country. But it is a promising start. Some of the pilot projects have succeeded dramatically. They offer a way out of what will otherwise be a biologically impoverished future. With the world population at 5.7 billion and sure to keep on growing rapidly until well into the next century, humanity has entered a dangerous environmental bottleneck. We hope--surely we must believe--that our species will come out the other side in better condition than when we entered. We should make it a goal to take as much of the rest of life with us as is humanly possible.

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