Mammals, fish, birds, amphibians, reptiles suffering major declines
ammals, fish, birds, amphibians, and reptiles the higher ani mals known collectively as vertebrates are suffering high rates of decline, reports a new study from the Worldwatch Institute. About one in four vertebrate species surveyed so far is in serious trouble - either declining sharply in numbers, limited to dangerously small populations, or facing pressure from land clearance, road building, excessive hunting and fishing, and other human activities.
"We are in the midst of a mass extinction, an event not seen since the disappearance of the dinosaurs 65 million years ago," says John Tuxill, a Research Fellow at the Worldwatch Institute and author of Losing Strands in the Web of Life: Vertebrate Declines and the Conservation of Biological Diversity. "But unlike the dinosaurs, we are not just contemporaries of a mass extinction we are the reason for it."
In 1996, the World Conservation Union (IUCN), in collaboration with over 600 scientists, published a groundbreaking survey of the status of animal life on Earth. According to their estimates, 25 percent of mammal and amphibian species, 11 percent of birds, 20 percent of reptiles, and 34 percent of fish species surveyed so far are threatened with extinction. In addition, another 5 to 14 percent of species in these groups are "nearing threatened status."
"The declining health of vertebrates is but one indicator of a decline in many facets of the natural world," said Tuxill. "Plants, insects, snails, and many other organisms are also threatened. Together, all of these life forms make up what scientists call biodiversity the rich diversity of life that underpins everything from food production to a host of essential medicines. Unlike other environmental losses, this one cannot be reversed. With biodiversity, nature doesn't give second chances."
"Even as we begin to appreciate the vast array of goods and services that diverse natural systems provide, most of what we are losing is still a mystery," Tuxill concluded. "We have barely begun to decipher the ecological relationships that keep natural systems running smoothly. If the IUCN's findings are updated regularly, and become as widely discussed as inflation or unemployment rates, we will have a powerful gauge for measuring the damage we are doing to natural systems."
Scientists estimate that extinction rates are now 100 to 1,000 times greater than normal and rising sharply. Since most species are unknown and unmonitored, the relatively well-studied vertebrates offer one of the best windows on why and how species are declining.
The leading cause of vertebrate declines is human destruction of old growth forests, wetlands, chaparral, and other rich habitats. Worldwide, over two-thirds of the earth's habitable land surface has been significantly disturbed by human activities. Nearly half of the world's 233 primate species are threatened, largely because of their dependence on large expanses of tropical forest, a habitat under siege around the globe. In hot spots of forest loss, such as Madagascar, the Atlantic rainforest of eastern Brazil, and Southeast Asia, roughly 70 percent of primate species face extinction.
Habitat alteration is less visible but equally severe underwater. 40,000 large dams and hundreds of thousands of smaller barriers plug up the world's rivers, altering water temperatures, seasonal flow patterns and other conditions that support fish. In the heavily altered Colorado River basin, 29 of 50 native fish species are either extinct or endangered. And 30 percent of the world's coral reefs which support the oceans' greatest concentrations of biological diversity are in critical condition from pollution, sedimentation, and destructive fishing and mining.
Tuxill also reports on over-hunting and over-fishing, the main dangers facing about one-fifth of all threatened species surveyed-propelled largely by commercial markets for wildlife meat, hides, and other products. Of particular concern are the unregulated "bushmeat" trade in Central and West Africa, and East Asian demand for medicinal products derived from animals. Some 36 sea horse species are threatened by the trade of an estimated 20 million sea horses each year for use in traditional Chinese medicines, in the aquarium trade and as tourist curios. Large mammals, reptiles, and fish are especially vulnerable to over-hunting a worrisome trend since these creatures have equally outsized ecological roles. In Central Africa, certain trees that rely on elephants to disperse their seeds failed to regenerate normally after elephant populations crashed from over-hunting.
An additional problem is the help, intentional and unintentional, that humanity gives to invasive species highly adaptable animals and plants which "hitchhike" with humankind to locations and ecosystems outside their native ranges. Invasive species are particularly devastating on islands and in isolated lakes and rivers, where native species are often unprepared to face exotic competitors.
The study examines a number of possible routes for reversing these mounting species declines. Tuxill points to promising strategies for conserving biodiversity in countries as diverse as Zambia, Nepal, and the United States, and calls for expanded steps at every level to manage the environment in more ecologically sound and socially equitable ways.
Governments have attempted to stem habitat loss by establishing national parks and wildlife refuges. Despite some notable successes, such networks of protected areas cannot by themselves save most species. At the national level, countries need to strengthen existing institutions like endangered species programs, and make the management of protected areas more collaborative, especially in cases where local residents have traditions of wisely managing natural resources. It is also essential to strengthen international laws and agreements for protecting biodiversity, like the Convention on Biological Diversity (which the United States has yet to ratify).
No system of laws or parks can ultimately protect the world's animals unless the underlying forces driving their destruction are contained. Stabilizing the world's population, reducing overconsumption by the world's middle and upper classes, and meeting the basic needs of billions of poor people are essential for maintaining and restoring the world's biological health.
"Either we redouble our efforts to protect species and reverse the problems degrading natural communities, or we will be left with depleted, far simpler ecological systems that no longer provide the material, aesthetic, and spiritual benefits we have long taken for granted," said Tuxill. "We still have the choice of saving most species-but our children may not."
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