THE SIXTH EXTINCTION
It Happened to Him. It's Happening to You.
The news of environmental traumas assails us from every side -- unseasonal storms, floods, fires, drought, melting ice caps, lost species of river dolphins and giant turtles, rising sea levels potentially displacing inhabitants of Arctic and Pacific islands and hundreds of thousands of people dying every year from air pollution. Last week brought more -- new reports that Greenland's glaciers may be melting away at an alarming rate.
What's going on? Are we experiencing one of those major shocks to life on Earth that rocked the planet in the past?
That's just doomsaying, say those who insist that economic growth and human technological ingenuity will eventually solve our problems. But in fact, the scientific take on our current environmental mess is hardly so upbeat.
More than a decade ago, many scientists claimed that humans were demonstrating a capacity to force a major global catastrophe that would lead to a traumatic shift in climate, an intolerable level of destruction of natural habitats, and an extinction event that could eliminate 30 to 50 percent of all living species by the middle of the 21st century. Now those predictions are coming true. The evidence shows that species loss today is accelerating. We find ourselves uncomfortably privileged to be witnessing a mass extinction event as it's taking place, in real time.
The fossil record reveals some extraordinarily destructive events in the past, when species losses were huge, synchronous and global in scale. Paleontologists recognize at least five of these mass extinction events, the last of which occurred about 65 million years ago and wiped out all those big, charismatic dinosaurs (except their bird descendants) and at least 70 percent of all other species. The primary suspect for this catastrophe is a six-mile-wide asteroid (a mile higher than Mount Everest) whose rear end was still sticking out of the atmosphere as its nose augered into the crust a number of miles off the shore of the present-day Yucatan Peninsula in Mexico. Earth's atmosphere became a hell furnace, with super-broiler temperatures sufficient not only to kill exposed organisms, but also to incinerate virtually every forest on the planet.
For several million years, a period 100 times greater than the entire known history of Homo sapiens, the planet's destroyed ecosystems underwent a slow, laborious recovery. The earliest colonizers after the catastrophe were populous species that quickly adapted to degraded environments, the ancient analogues of rats, cockroaches and weeds. But many of the original species that occupied these ecosystems were gone and did not come back. They'll never come back. The extinction of a species, whether in an incinerated 65-million-year-old reef or in a bleached modern-day reef of the Caribbean, is forever.
Now we face the possibility of mass extinction event No. 6. No big killer asteroid is in sight. Volcanic eruptions and earthquakes are not of the scale to cause mass extinction. Yet recent studies show that troubling earlier projections about rampant extinction aren't exaggerated.
In 2007, of 41,415 species assessed for the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species, 16,306 (39 percent) were categorized as threatened with extinction: one in three amphibians, one quarter of the world's pines and other coniferous trees, one in eight birds and one in four mammals. Another study identified 595 "centers of imminent extinction" in tropical forests, on islands and in mountainous areas. Disturbingly, only one-third of the sites surveyed were legally protected, and most were surrounded by areas densely populated by humans. We may not be able to determine the cause of past extinction events, but this time we have, indisputably: We are our own asteroids.
Still, the primary concern here is the future welfare of us and our children. Assuming that we survive the current mass extinction event, won't we do okay? The disappearance of more than a few species is regrettable, but we can't compromise an ever-expanding population and a global economy whose collapse would leave billions to starve. This dismissal, however, ignores an essential fact about all those species: They live together in tightly networked ecosystems responsible for providing the habitats in which even we humans thrive. Pollination of flowers by diverse species of wild bees, wasps, butterflies and other insects, not just managed honeybees, accounts for more than 30 percent of all food production that humans depend upon.
What will the quality of life be like in this transformed new world? Science doesn't paint a pretty picture. The tropics and coral reefs, major sources of the planet's biological diversity, will be hugely debilitated. The 21st century may mark the end of the line for the evolution of large mammals and other animals that are now either on the verge of extinction, such as the Yangtze River dolphin, or, like the African black rhinoceros, confined to small, inadequately supportive habitats. And devastated ecosystems will provide warm welcome to all those opportunistic invader species that have already demonstrated their capacity to wipe out native plants and animals. We, and certainly our children, will find ourselves largely embraced by a pest and weed ecology ideal for the flourishing of invasive species and new, potentially dangerous microbes to which we haven't build up a biological resistance.
Of course people care about this. Recent surveys show a sharp increase in concern over the environmental changes taking place. But much of this spike in interest is due to the marked shift in attention to climate change and global warming away from other environmental problems such as deforestation, water pollution, overpopulation and biodiversity loss. Global warming is of course a hugely important issue. But it is the double whammy of climate change combined with fragmented, degraded natural habitats -- not climate change alone -- that is the real threat to many populations, species and ecosystems, including human populations marginalized and displaced by those combined forces.
Still, human ingenuity, commitment and shared responsibility have great potential to do good. The IUCN Red List now includes a handful of species that have been revived through conservation
efforts, including the European white-tailed eagle and the Mekong catfish. Narrow corridors of protected habitat now connect nature preserves in South Africa, and similar corridors link up the coral reefs of the Bahamas, allowing species in the protected areas to move back and forth, exchange genes and sustain their populations. Coffee farms planted near protected forests and benefiting from wild pollinators have increased coffee yields. New York's $1 billion purchase of watersheds in the Catskill Mountains that purify water naturally secured precious natural habitat while eliminating the need for a filtration plant that would have cost $6 to $8 billion, plus annual operating costs of $300 million. Emissions of polluting gases such as dangerous nitrogen oxides have leveled off in North America and even declined in Europe (unfortunately emissions of the same are steeply rising in China). Plans for reflective roofing, green space and increased shade to cool urban "heat islands" are at least under consideration in many cities.
These actions may seem puny in light of the enormous problem we face, but their cumulative effect can bring surprising improvements. Yet our recent efforts, however praiseworthy, must become more intensive and global. Any measure of success depends not only on international cooperation but also on the leadership of the most powerful nations and economies.
The first step in dealing with the problem is recognizing it for what it is. Ecologists point out that the image of Earth still harboring unspoiled, pristine wild places is a myth. We live in a human-dominated world, they say, and virtually no habitat is untouched by our presence. Yet we are hardly the infallible masters of that universe. Instead, we are rather uneasy regents, a fragile and dysfunctional royal family holding back a revolution.
The sixth extinction event is under way. Can humanity muster the leadership and international collaboration necessary to stop eating itself from the inside?
Michael Novacek, a paleontologist, is senior vice president and provost of the American Museum of Natural History. He is the author of "Terra: Our 100-Million-Year-Old Ecosystem -- and the Threats That Now Put It at Risk."