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Ecological ground zero

According to many biologists, the earth is in the midst of a mass extinction, a dying off of plants and animals on a scale seen only a few times in the planet’s 4.6-billion-year history.

The most recent mass extinction, which wiped out the dinosaurs 65 million years ago, was probably caused by the explosive impact of a meteorite. In contrast, the present extinction is taking place quietly, a result of the wholesale destruction of natural habitats by people around the globe. Most of the species that are disappearing have not even been discovered, let alone described by science. A rare orchid here, a tiny arthropod there: when the last member of a species dies, it goes unseen and unrecorded.

Species are disappearing today at a rate estimated at from 100 to 1,000 times the normal extinction rate. Unless something is done, this century will mark the end of the present Cenozoic Era, says Harvard biologist Edward O. Wilson. The next phase of the earth’s history, he says, might best be called the “Eremozoic Era,” or the Age of Loneliness.

But the situation is not hopeless. Biodiversity is not evenly distributed across the earth, but rather is concentrated in certain areas. A decade ago, British ecologist Norman Myers created the concept of “biodiversity hotspots” to identify these critical areas and help guide the work of conservation organizations. In a recent article appearing in the British journal Nature, Myers, along with Conservation International President Russell A. Mittermeier and others, presented a comprehensive case for focusing conservation efforts on these hotspots, in order to get the most protection for the money.

“The hotspots concept can turn a profound problem into a magnificent opportunity,” says Myers. “I can think of no other biodiversity initiative that could achieve so much at comparatively small cost.”

Rich and under siege. The Nature article identifies 25 hotspots that cover only 1.4 percent of the earth’s land area (the study does not include aquatic habitats) yet account for a staggering 44 percent of all vascular plant species and 35 percent of four vertebrate groups. The authors used two factors for determining hotspots: number of endemic species (i.e., found nowhere else) and degree of threat.

To qualify as threatened, an area must retain less than 30 percent of its original natural habitat. So while the Amazon basin holds an immense number of endemic species, much of it remains intact, and so it does not qualify as a hotspot. But Brazil’s Atlantic forest, also a treasure trove of species, today exists only as remnants amounting to some 5 percent of its original area.

The article identifies seven hotspots in Latin America and the Caribbean (see map). Of these, three rank among the world’s five most critical hotspots: the tropical Andes, Brazil’s Atlantic forest and the Caribbean. The tropical Andes qualifies as one of the world’s two “hyper-hot” areas for its “exceptional” numbers of endemic plants—some 20,000 in all—as well as its number of endemic vertebrates, the highest in the world.

Some 38 percent of the total area of the world’s hotspots have been designated as parks and reserves, although real protection is often very limited. The remaining area has no protection whatsoever. Although outright protection is the best option where possible, say the authors, multiple use in places with extensive human settlements could still be effective.

The cost of reversing the trend is high, but not unrealistic. The authors estimate that $20 million per hotspot annually over the next five years would go far toward achieving effective protection. While this is far more than is presently being spent, the authors point out that it is only twice the cost of a single mission to Mars, which is justified in large part on biodiversity grounds—the search for extraterrestrial life. It is also far less, they say, than the $1.5 trillion that they estimate is spent annually worldwide on subsidies that encourage environmental degradation.

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