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Humans and their predecessors have been in competition with other life forms for millions of years.  Soon, the rapid growth of our population may squeeze the diversity of life out of existence.

Following is an original version of an essay published in the Chronicle of Higher Education (1/26/01), summarizing the gist of my next book, Sparing Nature:

Saving the Environment, 

One (Fewer) Child at a Time

English economist Thomas Robert Malthus made quite a long-lasting name for himself back in 1798, when he proposed that the growth of the world’s human population would outstrip the growth of resources. His Essay on Population was a cornerstone of Darwin’s theory of natural selection, and inspired population control activists during their heyday in the 1960s and early ‘70s. But by 1998 the 200^th anniversary of Malthus’s initial publication went almost without notice. The following year people were more concerned about "Y2K" than "Y6B" – the year our human population hit a count of six billion – although the latter will have a more significant and lasting bite. The popular press and the general public saw no Malthusian implications for the arbitrary number of six billion.

Many if not most Americans seem equally oblivious to the rising number of plant and animal extinctions. Estimates vary greatly, as we are just coming to grips with the unfolding drama, but at current rates we may lose up to half of earth’s plant and animal species within the next century. Surviving species will lose inestimable genetic variability and the potential to adapt as their populations dwindle, thus limiting the effectiveness of natural selection.

I am always astounded by the reaction of my students when I tell them about the mass extinction that is going on today. It is the sixth such extinction event that we know of, on par with that which killed off most dinosaurs. My students look at me as if this were breaking news. Scientists have known about the high rate of extinction around the globe for decades, yet students hear about little more than the panda this year and the black rhino next year. Sad losses, but who really cares? So I am left to wonder what the students have been learning all these years. And if they don’t know what is happening, the general public has little or no chance of recognizing the threats to our planets biodiversity.

There may be a way to awaken the apathetic (or blissfully ignorant) public. It certainly catches my students’ attention when I note that the two profound trends of human population growth and biodiversity loss are inextricably intertwined. But not inexplicably. Quite simply, we take up space to live, work, and grow our food. That leaves less room and resources for other species. We may or may not be outstripping our own resources yet, but in the process we are subsuming the resources needed by other living beings. We are living not so much on borrowed time as borrowed land and water.

To be sure, arcane graphs of human population growth and species extinctions don’t seem to have the visual impact of, say, an asteroid hitting the earth and knocking out 70% of living species – as happened in the last mass extinction. But the effect of population growth is no less real. It is just harder to see.

Perhaps that is why Malthus has been much maligned over the years. More than 200 years after his dire predictions, the human population is still growing and we seem to have adequate resources. Malthus did not foresee the technological advances that allowed us to garner necessities like food and fuel from seemingly impenetrable environments, thus delaying the exhaustion of resources that he predicted. True, the famine and pestilence he realized would be a consequence of our rapid growth do recur throughout the world, but most people blame poor management rather than any overriding principle of limited resources.

Technically, according to Joel Cohen in How Many People Can the Earth Support, if everyone lived under more modest conditions than those we enjoy in the United States, there should be sufficient food, energy, and water for the population to continue to grow. But such technicalities are of little solace to a starving family in Ethiopia – and hardly a goal that consumption-loving Americans want to embrace.

The key question, however, concerns not how many people the earth can "support," but how many it can sustain for a long period of time. And this is where the demise of earth’s biodiversity comes in to play.

University ecologists teach that living creatures on this planet provide us with many unheralded "services," including plants absorbing the carbon we spew into the air, microbes enriching the soil, and insects pollinating the plants we eat. The list goes on endlessly. It is becoming increasingly apparent from a number of ecological studies that if we reduce the biodiversity in ecological systems, we tamper with their sustainability. When an ecosystem becomes unsustainable and collapses, we imperil nature’s services and jeopardize our own resource base. Malthus comes back to haunt us.

One possible solution is conservation. People around the world are making noble efforts to set aside lands for nature to continue its work. "Hot-spots" of rich biological diversity have been identified and targeted for conservation. But hot-spots also tend to be in places where the human population is growing most rapidly.

All the conservation in the world will come to naught as long as the pressure from more and more humans continues. We see that outcome all the time. For example, there is global interest in saving the gorilla from extinction, and lands set aside for them. But a starving man who sees the gorilla as an easy target for "bush-meat" doesn’t share that concern. Food is food, and a few well-aimed guns can scare off legions of conservationists who stand between a man and a family meal. Americans are little different, and will allow richly diverse forests to be felled for grazing land so they can toss a juicy steak on the grill. Or, more subtly, conservation areas have been flooded by the construction of dams meant to provide water to urban populations. Priorities can change as populations grow.

In the time it takes me to teach my 10-week course on human ecology, the human population of the world grows by a number greater than the count of people in my home state, Ohio. Those new people need sustenance. What they take is largely a matter of space, but water and other resources are also drained away for our own purposes. The result is extinction of other plants and animals that need the same things.

People may not get excited about the loss of a rare nematode, but they might sit up and listen if they know that extinctions threaten their very livelihood. Nature’s services are under threat from our natural procreative habits, but there is something we can do about it. The greatest conservation measure humans can take is to halt the growth of our population. It is the only way we can sustain ourselves and the planet’s ecological health.

There are two ways to halt population growth. One is to increase the death rate. That is why Malthus saw famine, war, and pestilence as the inevitable outcome of the exponential growth of human numbers. But in Africa, for example, even with rampant starvation, wars, and an AIDS epidemic, the population is still growing. Raising the death rate enough to counteract the birth rate would require horrific levels of bloodshed and disease. Africa is not alone. Population growth, Malthusian consequences, and biodiversity loss are endemic on every continent, including our own. This is not somebody else’s problem.

A far more palatable means of population reduction is to lower the birth rate. It is relatively easy to reduce the number of pregnancies – we know what causes them. It is just not always easy for people to understand the consequences of pregnancies. We need to educate them.

We can provide the necessary tools, for family planning at is simply a matter of education. The federal government tried to do that, but last year a short-sighted congress stood in the way. It may be easy to sit in congress and tie American funding of global family planning clinics to popular moral principles espoused by vocal members of the electorate. There’s always next year, after the election. Family planning is needed in every country, including our own. And it is the most effective conservation tactic we have. Who in congress would object if they saw the connection? The electorate needs to see it as well.

Yet the connection eludes many, starting with university graduates who vote and consume and have babies. Many of these graduates also teach the next generation, unaware of how the world works, or, more importantly, how the world may not work in the near future. Thus the first point of intervention in conserving our natural resources is education about population growth and the extinction of plants and animals. We need to build a bridge to the 22^nd century, and the time to start is now. At the beginning of the 20^th century, Malthus knew the day would come.

Jeffrey K. McKee is an associate professor of anthropology at The Ohio State University. His most recent book is The Riddled Chain – Chance, Coincidence, and Chaos in Human Evolution (Rutgers University Press, 2000).