Endangered Species

By the estimate of one of the world's most respected conservation biologists, an average of 27,000 species may be disappearing each year.1 This is thousands of times higher than the natural rate of species extinctions. Among the direct causes of this loss of other living beings‹our only known companions in the universe‹are deforestation and the ongoing destruction of wetlands and coastal habitat. These activities relate especially to the human tendency to convert wilderness into agricultural land, and agricultural land to residential, industrial, commercial and recreational use.

"The conversion of wilderness to agricultural land, or other forms of human use, is fundamentally linked to human population expansion and economic development," writes Princeton University biologist Andrew P. Dobson. "Obviously there are many subtleties in this process; nevertheless, it is hard to escape the basic fact that an increasing human population requires larger areas of cropland to provide food, as well as areas in which to live and process the resources that make human civilization viable."2

The issue is not merely the complete conversion of wild land for human use, but the increasing fragmentation of forests and other wild areas. Wild plant and animal populations need certain minimum uninterrupted land areas to survive and thrive. Often the patches of wilderness left intact are insufficient to sustain functioning ecosystems. Moreover, for every acre of forest land converted to working farm or pasture, another acre becomes too degraded either to contribute to food production or to maintain biologically diverse ecosystems.

While the global trend toward urban living tends to concentrate human population growth into already settled areas, urbanization poses its own threats to species and ecosystems. Pavement is the ultimate destroyer of wild habitat. The pollution caused by concentrations of humanity can affect distant habitats, especially in coastal areas. City dwellers depend on farms that can be half a globe away, while the supply networks for their food and other needs stretch across the planet.

Population growth, often combined with growth in per capita resource consumption, can be the critical factor pushing an ecosystem past natural levels of tolerance and resilience. In many ecosystems, extinction rates‹including the future extinctions set in motion by today's environmental impacts‹appear to accelerate from low levels as the last 20 to 30 percent of a habitat is destroyed.3 This observation could help explain why extinction rates are spiking sharply upward as world population, which took until 1950 to reach 2.5 billion people, approaches 6 billion people in 1999.4

The extinction of each nonhuman species represents the destruction of something precious in and of itself, an unfathomable part of nature that once had its own independent existence. But the loss also affects human interests beyond the spiritual and esthetic. Our well-being depends, in ways we cannot fully understand, on the services the planet's millions of plant and animal species provide. An estimated 70 percent of the drugs on which modern medicine relies are derived from compounds found in nature. These came from only about 250 plant species (traditional medicine relies on several thousand species),5 yet only one plant species in thousand has been examined for its medicinal properties. At the very moment in human history when we have the tools for studying and applying genetic information from nature, we are discarding forever much of the planet's genetic heritage. One consequence of the destruction and fragmentation of forests and the growing use of pesticides on farms is the decline of bees and other pollinators. The danger here is more than the loss of the wonder that bees offer us or the threat to the world¹s supply of honey. The danger is that staple crops that require pollination to reproduce‹and most do‹could fail. By one estimate, one out of every three mouthfuls of food depends on pollination by insects and other animals.6 Without bees and other pollinators, many people may be left without varied and inexpensive sources of food. Losing species, we lose more than we know.