The whole world really
is in our hands,
leading ecologists assert
BY JANET BASU
And God blessed them, and said unto them, "Be fruitful, and multiply, and replenish the earth, and subdue it: and have dominion over the fish of the sea and over the fowl of the air, and over every living thing that moveth upon the earth." Genesis 1:28
It took a strong dose of chutzpah for the writer of Genesis to imagine that Adam and Eve held dominion over "every living thing," over beasts as ungovernable as tigers and whales, forces as terrifying as plague and drought. Now, thousands of years later, some of the world's most respected scientists are saying that this dominion is now accomplished. Human activities have so much impact that we have become a "force of nature" in our own right.
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In a special section of the July 25 issue of Science, scientists from Stanford and elsewhere document the ways in which humans are transforming the land, the water and even the atmosphere of Earth more rapidly and at a greater scale than these things have been changed at any time in the history of our species. They suggest actions that can be taken to slow the pace of change by using resources more sustainably.
"In a very real sense, the world is in our hands. . . . Humanity's dominance of Earth means that we cannot escape responsibility for managing the planet," say the authors of the lead article. They are Stanford biological sciences Professors Peter Vitousek and Harold Mooney; ecologist Jerry Melillo of the White House Office of Science and Technology Policy; and marine ecologist Jane Lubchenco of the University of Oregon, who is past president of the American Association for the Advancement of Science.
The special issue of Science includes five other scientific papers documenting the extent to which ecosystems are dominated by humans, plus a news section and an editorial by Gro Harlem Brundtland, a leading environmentalist and the former prime minister of Norway.
Every organism modifies its environment, said Vitousek, who is the Clifford G. Morrison Professor of Population and Resources Studies, and when it comes to humanity's impact, we usually think of "human-dominated ecosystems" in terms of plowed fields, harvested forests and urban landscapes. "Now, that term applies with greater or lesser force to all of Earth," he said. "Many ecosystems are dominated directly by humanity, and no ecosystem on Earth's surface is free of pervasive human influence."
Lubchenco said, "We tend to think of the forces of nature as being massive geological cataclysms like volcanoes or floods or hurricanes. Humans, by virtue of our numbers and our technical capabilities, have emerged upon the scene as a major force of nature [as well]. It has happened very quickly, and it already has resulted in unanticipated, major consequences."
Lubchenco spoke in a telephone interview from Washington, D.C. By coincidence, on July 24, the day before the Science special issue was published, she and six other scientists, including Stanford climatologist Stephen Schneider, briefed President Clinton and Vice President Gore on one aspect of human-caused global change (see related story).
In their Science article, Vitousek, Mooney, Lubchenco and Melillo present an overview of the major ways that the human enterprise has transformed the planet, and suggest methods to manage this transformation so that the species and ecosystems we depend on can be sustained for the future.
Among their examples of human impact:
- The carbon dioxide concentration in
the atmosphere has increased by nearly 30 percent since the
beginning of the Industrial Revolution.
- More than half of all accessible
fresh water is used by humans. "Of all the environmental security
issues facing nations, an adequate supply of clean water will be
the most important," the scientists predict.
- One-third to one-half of Earth's
land surface has been transformed by human action. Some changes
have been to humanity's benefit; some have altered or destroyed
ecosystems that we depend on, both on land and in nearby
waterways.
- About a quarter of the bird species
on Earth have been driven to extinction.
- Two-thirds of marine fisheries are
fully exploited, over-exploited or depleted.
- Humans have deposited long-lasting,
toxic chemicals in soil and water around the globe; we've also
rearranged the world's living organisms with global transfers of
invasive species that crowd out the natural habitats of birds and
animals.
- Humanity fixes more nitrogen from the air than is fixed by all natural processes combined. Nitrogen, essential for plants to grow, must be chemically altered or "fixed" to be usable. While abundant usable nitrogen is good for crops, it also supports invasive species. Along coastlines, nitrogen from fertilizer run-off feeds algal blooms including toxic "red tides."
Mooney, who is the Paul S. Achilles Professor of Environmental Biology, said that it is both the massive scale of global change and the rapidly accelerating rate of change that scientists are concerned about. Mooney, past president of the Ecological Society of America and currently secretary-general of the International Council of Scientific Unions, the "United Nations" of scientific societies, said that given time, most ecosystems adjust to change. But too much change at an accelerated rate could leave vast areas depleted of key species and the complex web of life that they and we depend on.
"The rates, scales, kinds and combinations of changes now are fundamentally different from those at any other time in history," Mooney and his co-authors write. "We are changing Earth more rapidly than we are understanding it." They called for work to reduce the rate of change, to stabilize the human "footprint" on the planet at a level that can sustain most species. That would involve slowing human population growth, and using resources efficiently so the wastes and byproducts of human activity do less harm to the environment.
They also called for accelerated efforts to understand human-caused global change, with more ecological research as well as more work to understand the social, economic and cultural forces that drive human actions on the environment.
"The message from the scientific
community is clear," said Lubchenco. "We are beyond arguing about
the science. We know enough to act. Our future and the quality of
our future depends on the extent to which we recognize our impact
[on the Earth] and take responsibility for using this power
wisely." SR