Before Brazil's great land rush, the emerald rain forests of Rondonia state were an unspoiled showcase for the diversity of life. In this lush territory south of the Amazon, there was hardly a break in the canopy of 200-ft.-tall trees, and virtually every acre was alive with the cacophony of all kinds of insects, birds and monkeys. Then, beginning in the 1970s, came the swarms of settlers, slashing and burning huge swaths through the forest to create roads, towns and fields. They came to enjoy a promised land, but they have merely produced a network of devastation. The soil that supported a rich rain forest is not well suited to corn and other crops, and most of the newcomers can eke out only an impoverished, disease-ridden existence. In the process, they are destroying an ecosystem and the millions of species of plants and animals that live in it. An estimated 20% of Rondonia's forest is gone, and at present rates of destruction it will be totally wiped out within 25 years.
Around the globe, on land and in the sea, the story is much the same. Spurred by poverty, population growth, ill-advised policies and simple greed, humanity is at war with the plants and animals that share its planet. Peter Raven, director of the Missouri Botanical Garden, predicts that during the next three decades man will drive an average of 100 species to extinction every day. Extinction is part of evolution, but the present rate is at least 1,000 times the pace that has prevailed since prehistory.
Even the mass extinctions 65 million years ago that killed off the dinosaurs and countless other species did not significantly affect flowering plants, according to Harvard biologist E.O. Wilson. But these plant species are disappearing now, and people, not comets or volcanoes, are the angels of destruction. Moreover, the earth is suffering the decline of entire ecosystems -- the nurseries of new life-forms. For that reason, Wilson deems this crisis the "death of birth." British ecologist Norman Myers has called it the "greatest single setback to life's abundance and diversity since the first flickerings of life almost 4 billion years ago."
Nearly every habitat is at risk. Forests in the northern hemisphere have fallen to lumbering, development and acid rain. Marine ecosystems around the world are threatened by pollution, overfishing and coastal development. It is in the tropics, though, that the battle to preserve what scientists call biodiversity will be won or lost. Tropical forests cover only 7% of the earth's surface, but they house between 50% and 80% of the planet's species.
But should people in developed countries care about the survival of tropical species never seen outside a rain forest? Yes, they should. Variety is the spice of life, goes the saying. Biologists would go further and argue that variety is the very stuff of life. Life needs diversity because of the interdependencies that link flora and fauna, and because variation within species allows them to adapt to environmental challenges. But even as the world's human population explodes, other life is ebbing from the planet. Humanity is making a risky wager -- that it does not need the great variety of earth's species to survive.