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The world should invest generously in an indispensable capital asset - the earth's rich complement of life, say Stanford biologist Paul Ehrlich and his Harvard colleague, sociobiologist E. O. Wilson.
In the lead article for a recent issue of Science magazine, Ehrlich and Wilson described the importance of biological diversity to humankind, and proposed worldwide cooperation in far- reaching conservation and restoration measures.
People depend upon "ecosystem services" provided by the complex interaction of many other living things, they wrote. Such interactions maintain the composition of the atmosphere, stabilize climate, generate and enrich soil, purify water and supply food. Preservation of these benefits is worthy of efforts on the scale of those recently invested in the Cold War, they argued.
Since the publication of his book The Population Bomb in 1968, Ehrlich has been warning that the exponential growth of the human population will someday exceed the planet's capacity to support it. In the Aug. 16 Science, he was joined by Wilson and other prominent biologists in arguing that worldwide loss of biodiversity is one of the mechanisms that will erode the life-supporting qualities of the earth.
The issue also included a news article on biodiversity issues; perspective articles by conservation biologist Michael Soule of the University of California-Santa Cruz, entomologist Terry Irwin of the National Museum of Natural History, biologist Harold Morowitz of George Mason University and geologist David Jablonski of the University of Chicago; and an editorial by Science editor Daniel Koshland.
In an interview, Ehrlich said that a new level of human cooperation is needed to get the world out of this quandary - a step beyond the individualism that millions of years of evolution have conditioned our species to seek. He said the crisis is now so clear that both individuals and nations will be able to understand the need to work together for common good - and that is the challenge of the era.
Ehrlich is director of the Center for Conservation Biology, Bing Professor of Population Studies and professor of biological sciences at Stanford. His books include Healing the Planet (1991), and he has written extensively on the interactions between humans and the environment. Ehrlich will deliver a topical lecture on "Feeding the World" on Friday, Feb. 7, at the meeting of the American Association for the Advancement of Science in Chicago.
Wilson is Baird Professor of Biological Sciences at Harvard and curator in entomology at Harvard's Museum of Comparative Zoology. He is widely regarded as the founder of sociobiology - the study of the genetic basis for social behavior.
In their joint article, Ehrlich and Wilson expressed grave concern that in recent centuries, and particularly during the past few decades, humans have been driving increasing numbers of wild species to extinction. More people seeking more food, water, timber, minerals and land are leaving less of life's necessities for other creatures.
Ehrlich summarized the situation with a quick lesson in global ecology: Sunlight is the income that drives nature's economy. Green plants convert a small part of it to chemical energy, some of which they use to live, with the rest available to support other life. The amount available each year is called global net primary production.
"Early in this century humans diverted or destroyed less than a tenth of the net primary production occurring on land, where the overwhelming majority of species exist. Today we claim 40 percent and are grasping for more. It's easy to understand why other forms of life are in retreat," Ehrlich said.
Wilson asserted that humans eliminate tens of thousands of species each year. By his reckoning, the current pace of extinction is thousands of times greater than the average rate since life first appeared on earth; one-quarter of all species could be eliminated within 50 years. Wilson bases his estimate upon studies of tropical rain forests, which harbor abundant life but are being rapidly cut and burned.
Even more significant are the qualitative differences between current extinctions and those of the past, Ehrlich and Wilson wrote. For the first time, the green plants that provide the energy basis for virtually all life are disappearing in large numbers.
"The services afforded by green plants and the other species they support are income, like interest or dividends, flowing from the capital value of nature. Preservation of that capital is essential if we are to continue reaping steady income from it," Ehrlich said.
The good news, Ehrlich said, is that people are awakening to the importance of biodiversity."
Diverse species are essential to the earth's ability to support life, he said, in the same way that different mechanical parts are essential to an airplane's ability to fly.
"Just as we know better than to strip parts off an airplane in which we are flying, so are we learning to refrain from removing life forms from ecosystems which are far more complicated than any airplane, and which we understand very incompletely," he said.
For decades, humanity has made substantial investments in biodiversity through such efforts as wildlife refuges, habitat restoration projects, seed banks and tissue culture collections.
Wilson and Ehrlich predict that while such measures may be sufficient to save particular species or certain genetic information for pharmaceutical or other specific purposes, it will take much larger expenditures to fully protect the capital value of biodiversity. Protecting a few favored species as "endangered" is often too little action, too late in the game.
"By the time a species is given endangered status, entire populations have been wiped out of certain habitats, reducing or severely threatening ecosystem services in those areas," Ehrlich said.
Ehrlich and Wilson advocate an end to development on relatively undisturbed land.
"Every new shopping center built in the California chaparral, every hectare of tropical forest cut and burned, every swamp converted to a rice paddy or shrimp farm means less biodiversity," they wrote.
In rich countries, they advocate limiting extractive activities like forestry, farming and fishing to sustainable levels.
In places where people are relatively poor, they see lowering birth rates as a critical step to halt the expansion of grazing and cultivation into virgin areas. They also propose more widespread land ownership: Landless, impoverished people too often face a choice between degrading the environment and dying.
In addition, they urge "global cooperative efforts" such as actions to reduce greenhouse gases and ozone-destroying compounds. To ease the burden on the poor, they recommend "massive assistance" in "a cooperative worldwide effort unprecedented in history."
Such a sweeping program for resource reallocation has stimulated lively debate. In a news article by Charles C. Mann in the same issue of Science, critics argued that even if people are reducing biodiversity at unprecedented rates, losses of species and ecosystem services will prove smaller than Ehrlich and Wilson expect. They propose that rates of speciation and extinction be studied more thoroughly before asking for additional sacrifices to preserve or replenish biodiversity.
"Apparently a few scientists would never call the fire department unless they could inform it of the exact temperature of the flames," Ehrlich answered in a letter in a subsequent issue of Science.
He said that while a handful of researchers labor to precisely measure the loss, these critics seemed willing to test the world's need for biodiversity by "a single vast irreversible experiment."
In their writings of the past two decades, Wilson and Ehrlich have argued that individual well-being is increasingly dependent upon the well-being of other people and other life, and offered a theory on why this may be hard for humans to accept.
Individuals want to maximize the number of their own genes and the time period over which the genes survive, wrote Wilson. For three and a half billion years of biological evolution, the genes of most organisms - including humans - have informed them to seek advantage over others.
By conquering threats like cave bears and the polio virus, people have eliminated most of the "checks" on human reproductive potential, Ehrlich says. With many more people able to have children, individuals who pass on as many genes as possible in the short term may actually undermine their own - and everyone's - long-term ability to pass on genes.
In Sociobiology (1974), Wilson explained that a long- term approach to passing on genes may be a better strategy. He wrote that individuals who parent one or two children who are able to survive and to produce offspring who repeat the process for many generations may be more successful than those who are followed by many descendants for a few generations, and none thereafter.
According to Wilson, unless we are able to perceive net benefit to ourselves in preserving and protecting other people and other life, the DNA in every cell of our bodies will protest any action we take to do so.
Ehrlich suggests that now, more than ever before, individual welfare is dependent on the welfare of others. It is becoming less and less possible for some privileged individuals to escape the consequences of adverse human impacts.
"You're right to assume that your own investment in nature may prove futile," Ehrlich said. "In fact, its full potential for return can only be realized if many others invest as well. But everybody's increasingly in the same boat. A major challenge of our era is to find a way to sail together."
Ehrlich points to coal-burning as an activity that contributes to the erosion of biological diversity and says, "If people stop burning coal, miners will be out of work. We need to be empathetic toward the people whose lives are going to change as we do things differently, and we need to afford choices that will motivate everyone to join in conserving natural capital and ensuring that the stream of ecosystem services will continue unabated."
As he contemplates the task ahead, Ehrlich draws encouragement from the recent political upheaval in Eastern Europe and the former Soviet Union.
"If I had told you three years ago that in 1991 the Soviet Union would be dissolved and Germany would be reunited, you would have thought I was nuts," he said. "People can effect cultural change very rapidly."
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