Too Many People

By EUGENE LINDEN

The state of the environment in the latter part of the next century will be determined largely by one factor: human population. If the species doubles its numbers by 2050, to nearly 11 billion, humanity may complete the devastation that accelerated so steeply in this century. Such unabated expansion in our numbers would continue to soak up the world's capital and prevent the poorer nations from making the necessary investments in technological development that might deter continued population growth.

If the worst occurs, countless millions will become environmental refugees, swamping the nations that tried to conserve their soil, water and forests. The great-grandchildren of today's young people would have to share the planet with only a ragged cohort of adaptable species dominated by rats, cockroaches, weeds, microbes. The world in which they survived would consist largely of deserts, patches of tropical forests, eroded mountains, dead coral reefs and barren oceans, all buffeted by extremes of weather.

The best hope for both humanity and other life-forms would be to cut human propagation in half, so the world's numbers do not exceed 8 billion by mid- century. (The only event in which the earth would achieve zero population growth or even shrinkage would be some environmental or social catastrophe.) The huge run-up in human numbers has foreclosed most options and shortened the amount of time available to come to grips with rising threats to the environment, contends systems analyst Donella Meadows, co-author of Beyond the Limits, which updates the controversial 1972 blockbuster The Limits to Growth. In the past, says Meadows, there were always new frontiers for exploding populations, as well as empty lands to accept wastes. No longer: most suitable areas have been colonized, most easy-to-find resources are already being exploited, and most dumping grounds have filled up. "If humans manage brilliantly starting very soon," Meadows believes, "it is possible the world might look better than it does now."

Still, for centuries humanity has confounded doomsayers by finding new supplies of food and energy. In the early 1970s some environmentalists interpreted temporary rises in food and oil prices to mean mankind was again pushing the limits of earthly resources, yet surpluses returned in later years. Julian Simon, among other economists, argued that this revealed a basic problem with the limits-to-growth argument. Price rises caused by scarcities, he argued, will always stimulate human ingenuity to improve efficiency and find new resources.

In the intervening years, however, there has been evidence that the market often fails to react as quickly as problems demand. The world took 15 years to respond to signs of ozone depletion in the upper atmosphere, but because ozone-destroying chemicals take 15 years to migrate to that stratum, the real delay amounts to 30 years. Moreover, these chemicals can remain in the atmosphere as long as 100 years. In addition, market forces often work perversely to hasten the demise of species and resources. The increasing appetite for bluefin tuna among sushi lovers and health-conscious diners has vastly increased the market price of the fish. But instead of dampening demand, the principal effect has been to encourage further fishing, to the point that the total number of the magnificent pelagic fish in the Atlantic has dropped 94% since 1970.

Demographers refer to such collisions between rising demand and diminishing resources as "train wrecks." As the world adds new billions of people in ever shorter periods, such potential conflicts happen almost everywhere. With most of the world's good land already under plow, a population of 11 billion human beings would probably have to make do with less than half the arable land per capita that exists today. That would set the stage for disaster, as farmers stripped nutrients from the soil, exacerbated erosion and gobbled up water and wild lands.

If population keeps building at the current rate, the most ominous effect is that millions of life-forms will become extinct. Humans, no matter how well behaved, cannot help crowding out natural systems. A survey of 50 countries by environmental researcher Paul Harrison showed that habitat loss, the most important factor leading to extinctions, rises in direct proportion to the density of the individuals that make up various species. Big animals often range over hundreds of square miles and increasingly collide with settlements. Smaller species, which make up most of nature's diversity, are affected by human activities in countless ways. Frogs, for example, are gradually disappearing around the world, perhaps because airborne pollutants are destroying their eggs. The crucial question is whether humankind can afford to exterminate large numbers of other species without ruining the ecosystems that also sustain us.

The world could avoid this question by reducing the burden placed on the biosphere by rising human numbers and the life-styles of rich nations. To do so, however, would require countries to treat these threats far more seriously than they did at the Earth Summit in Brazil last June. The affluent nations must move their economies more rapidly toward patterns of production and consumption that recognize the limits of what the earth can provide and what wastes it can accommodate. The poorer nations must make monumental efforts to remove incentives for people to have large families. This will require massive social change, including better education and improved access to family planning. With each passing year, it becomes more likely that the fastest- growing nations will be forced to adopt coercive measures, as China has, if they are to stabilize their numbers.

If none of this takes place, what might the earth look like? Author Meadows predicts that at its best, the typical landscape might resemble the Netherlands: a crowded, monotonous tableau in which no aspect of nature is free from human manipulation. Other analysts look to the history of island cultures because they tend to reveal how the environment and humans respond when burgeoning populations put stress on an isolated ecosystem.

Easter Island in the Pacific provides a cautionary example. When Europeans first landed there in 1722, they found 3,000 Polynesians living in extremely primitive conditions on the island amid the remnants of a once flourishing culture. The story of Easter Island is one of ecological collapse that began around the year 1600, when a swollen population of 7,000 stripped the island of trees, depriving inhabitants of building materials for fishing boats and housing. As the populace retreated to caves, various clans warred over resources, then enslaved and later cannibalized the vanquished. By the time Europeans arrived, the beleaguered survivors had forgotten the purpose of the great stone heads erected during Easter Island's glory days.

The tropical island nation of Mauritius in the Indian Ocean presents a more hopeful case study, according to environmental historian Richard Grove of Cambridge University. Mauritius is nearly as densely peopled as Bangladesh, yet manages to support healthy ecosystems and a booming economy. Nearly 200 years ago, the island's French settlers became alarmed by the cutting of ebony forests that caused severe erosion and had led to the extinction of the dodo bird. By the end of the 18th century, the locals had developed a full set of environmental controls, including strict limits on tree cutting. In recent years, Mauritius has launched a successful education effort to stabilize population growth. The country now ranks among the most prosperous in Africa. "I would be much less pessimistic about the future if the rest of the world could act like Mauritius," says Grove.

The world no longer has the leisure of the two centuries Mauritius took to develop a conservation ethic. In the past, natural forces shaped the environment. Now, unless a new round of volcanism erupts worldwide or a comet courses in from outer space, human activities will govern the destiny of earth's ecosystems. It may soon be within human power to produce the republics of grass and insects that writer Jonathan Schell believed would be the barren legacy of nuclear war. If humanity fails to seek an accord with nature, population control may be imposed involuntarily by the environment itself. Is there room for optimism? Yes, but only if one can imagine the people of 2050 looking back at the mad spasm of consumption and thoughtless waste in the 20th century as an aberration in human history.