by E. O. Wilson
The biosphere that gives us life is wondrously rich. The number of organisms composing it is astronomical: One million trillion insects are believed to be alive on the planet at any one time; they in turn are beggared by the bacteria, ten billion of which may reside in a single pinch of soil. And so great is the diversity of life-forms that we still have not taken its measure. During the past two centuries biologists have discovered and given formal names to somewhat more than 1.5 million species of plants, animals, and microorganisms, yet various methods of estimation place the number of all species on Earth, known and still unknown, between 3 million and 100 million.
In spite of this immense complexity, perhaps because of it, the biosphere is also very fragile. Although it appears robust, it is actually a hollow shell around the planet so thin it cannot be seen edgewise from an orbiting spacecraft. Its teeming organisms are ill equipped to withstand humanity's relentless assault on the habitats in which they live. Our species, at more than six billion strong and heading toward nine billion by mid-century, has become a geophysical force more destructive than storms and droughts. Half the world's forests are gone. Tropical forests in particular, where most of Earth's plant and animal species live, are being clear-cut at the rate of perhaps one percent a year. In shallow waters from the West Indies to the Maldives many of Earth's coral reefs are literally fading away. Polluting, damming, and the introduction of alien organisms are causing the wholesale extinction of native aquatic species. Greenhouse warming, by edging climatic zones poleward faster than flora and fauna can emigrate, threatens the existence of entire ecosystems, including those of the Arctic and other hitherto least disturbed parts of the world.
Researchers generally agree that extant species are now vanishing at least 100 and possibly as much as 10,000 times faster than new ones are being born. Many experts believe that at the present rate of environmental change half the world's surviving species could be gone by the end of the century.
Is there a way to divert the human juggernaut and save at least most of the remaining natural world? A providential arrangement in the geography of life makes it at least possible. Biodiversity is not distributed uniformly over land and sea. A large part of it is concentrated in a relatively small number of coral reefs, forests, savannas, and other habitats scattered on and around different continents. By preserving these special places, biologists have come to agree, it should be possible to accommodate the continuing human surge while protecting a large part of Earth's threatened fauna and flora.
the most precious of the special places are the hotspots, which conservation
biologists define as natural environments containing exceptionally large
numbers of endangered species found nowhere else. The most familiar
hotspots include the Philippines, California's Mediterranean-climate
coast, and Madagascar. Less well-known are Choco-Darien-Western Ecuador,
the Western Ghats of India, and the Succulent Karoo of South Africa.
Just 25 of the hottest of these hotspots occupy 1.4 percent of the planet's
land surface, roughly equivalent to Alaska and Texas combined, yet are
the exclusive homes of 44 percent of Earth's plant species and 35 percent
of its birds, mammals, reptiles, and amphibians. Increasingly, these
areas, among the biologically most opulent and fascinating places on
Earth, have become the focus of global conservation efforts. Their plight
is stark evidence of humankind's deadly impact on nature, and their
attempted rescue a beacon of hope.