Earth in the balance - could tilt either way

Life on Earth stands at a significant crossroad. Over the past 10,000 years, Homo sapiens have been wildly successful, colonizing continents, defeating a great proportion of natural enemies, and replacing forests, grasslands, and swamps with agricultural fields, roadways, and cities. Since 1960, our population has doubled to 6 billion; despite a slowing rate of growth, it will probably peak at between 8 and 10 billion later this century.

We also live in the midst of a mass extinctions, the greatest extermination of living species since the end of the dinosaurs. Estimates for current extinction rates range from 100 to 10,000 times prehuman levels, with most around 1,000 times the natural level. Whatever the rate, it is projected to rise steeply as remaining wild land is developed and nonindigenous species are introduced through human commerce.

What's at stake in the 21st century, Edward O. Wilson argues in "The Future of Life," is nothing less than the integrity of the planet and the magnificence of life itself. At current rates, half of the Earth's plant and animal species will cease to exist by the end of the century, forever impoverishing the human experience, materially and spiritually.

Wilson's pronouncements carry a great deal of weight. Wilson, an expert on biodiversity, is widely regarded as one of the world's greatest living scientists. A Harvard professor for more than four decades, he has received many of the world's top prizes in science and conservation, and has written two Pulitzer Prize-winning books, as well as the best-selling "The Diversity of Life" (1992).

He's also a beautiful and gifted writer, able to accurately convey not only the content of scientific research, but also its broader social, political, and moral implications. While grounded in vigorous, peer-reviewed science, "The Future of Life" is elegant and moving, a pleasure to read despite the gravity of its message.

Wilson argues that the central challenge facing humanity in the new century is to raise the standard of living of the world's growing poor, while preserving as much of the rest of life as possible. He's optimistic that by 2100 our impact on the biosphere will begin to wane, largely because our population will finally be shrinking, instead of rising. But between now and then, humanity - and the rest of life - must pass through what Wilson calls "the bottleneck," a time of intensifying population and environmental pressures. The stakes are enormous.

People are threatened because we may overwhelm the natural systems we depend on. China, the epicenter of population pressure, is already backed against a wall. More people require more food and irrigation, but the country is using up its freshwater supply. Since 1972, the lower Yellow River has gone bone dry for part of every year - 226 days in 1997 - resulting in billions of dollars in crop losses. From 1965 to 1995, Beijing's water table fell by 32 feet, and nearly half of China's 617 cities now suffer water shortages.

There are lots of practical reasons to protect the natural world. By one estimate, it provides humanity with $33 billion a year in free ecosystem services including resource production, climate regulation, and pollution removal. In recent years, many rare or nearly extinct species have been discovered to contain chemical or genetic innovations that can be used to treat diseases or improve crop production. Biodiversity is worth a great deal to our pocketbooks alone.

But Wilson provides an additional and, to my mind, more compelling argument: We evolved in nature, and its presence is part of what it is to be human. Using evidence from human genetics, cognitive science, child development, and theology, Wilson shows that our species is hardwired to need - perhaps, love - the natural world from which we sprung. "To conserve biological diversity is an investment in immortality," he writes, as it serves as a survival mechanism for ourselves and our species.

Wilson concludes that our species must embrace our role as nature's mind, as stewards over the rest of life with which we evolved. He then outlines a strategy to protect most of the remaining ecosystems and species. Among the key elements:

• Preserve the world's hotspots and the great forests of Canada, Russia, and the tropics.

• Cease logging of old-growth forests.

• Support population planning and sustainable development policies.

"In the end ... success or failure will come down to an ethical decision," Wilson writes, "one on which those now living will be judged for generations to come."

• Colin Woodard is author of "Ocean's End: Travels Through Endangered Seas" (Basic).

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