Academic journal article Environmental Health Perspectives

Population Equation: Balancing What We Need with What We Have

Academic journal article Environmental Health Perspectives

Population Equation: Balancing What We Need with What We Have

Article excerpt

Planet Earth, now home to about 6.5 billion human beings, has thus far disproved the doomsayers. In 1798, Rev. Thomas Robert Malthus predicted that population would outrun food supply on the assumption that human numbers would increase at a geometric rate while food would be limited to arithmetic increases. Then, in 1968, Stanford University professor Paul R. Ehrlich issued a similar warning in his book The Population Bomb, in which he predicted that hundreds of millions of people would die of starvation in the 1970s and 1980s.

Both men underestimated humanity's resourcefulness--as well as its scientific and technological acumen--in figuring out how to provide for its growing numbers. Still, there's little doubt that the Earth's human carrying capacity has a limit. And growth can't continue indefinitely without more of the significant environmental health impacts we are already seeing. In addition to documenting exactly how much growth is occurring, scientists are now interested in trends reflecting where such growth is occurring and the effect of factors such as consumption rates and migration on sustainability of the Earth's resources.

Maximum Capacity

Nobody really knows what the planet's human carrying capacity is. Some, like Cornell University ecology and agriculture professor David Pimentel, contend that the Earth has already passed that point. Citing high malnutrition rates in the world, Pimentel estimates that the Earth's carrying capacity--providing a quality life for all inhabitants--would appear to be about 2 billion. Other estimates go to both extremes. In a 1995 Cato Institute essay titled "The State of Humanity: Steadily Improving," Julian L. Simon, the late University of Maryland economist, wrote, "We have in our hands now--actually in our libraries--the technology to feed, clothe and supply energy to an ever-growing population.... Even if no new knowledge were ever gained ... we would be able to go on increasing our population forever." On the other end of the spectrum, in 1971--three years after writing The Population Bomb--Ehrlich placed the limit at 500 million.

Others suggest that humans are already finding a way to take care of the population problem as evidenced by declining birth rates everywhere in the world. Declining birth rates don't necessarily translate into declining populations, however. The United Nations (UN) Population Division projects that by 2050, global population could reach 9.1 billion.

This greater global population will differ from the current one in several ways. The population growth of the developed world has slowed to a crawl; fertility rates are on the decline and in some countries, such as Italy and Japan, population itself is projected to peak in five years. But poor countries will experience large increases for decades to come. Meanwhile, the UN points out that in 2007, for the first time in history, the global population will cross over from being predominantly rural to mostly urban, and that that trend will continue indefinitely.

"Most of the growth that's going to happen in the next twenty, thirty years is going to be happening in the poor countries--it's going to happen mostly in the cities, and mostly in the slums of the cities," says John Bongaarts, vice president of policy research at the nonprofit Population Council. "Most of the next two or three billion people will end up in the slums of the poorest countries."

Like many demographers, Bongaarts sees the decline in fertility rates, mostly in the industrial world, as the emerging worldwide norm. This means, he says, that at some point the poorer countries will reach the same stabilization point that the developed world has achieved and that global population will one day decline. He projects that peak will be reached at about 9.5 billion people.

Perhaps surprisingly, population's relationship to health and environmental impacts is often ignored or glossed over by policy makers. …

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