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At 29, Gretchen Daily is a rising star of population biology. She works at both UC-Berkeley’s Energy and Resources Group and Stanford University’s Center for Conservation Biology on a fellowship specifically created for her. Daily recently made news with a paper called “Optimum Human Population Size” in the July issue of the academic journal Population and Environment. She and co-authors Paul (of “The Population Bomb” fame) Ehrlich and Anne Ehrlich argued that overpopulation is not a future possibility but a present reality. They calculated that the earth can only support 1.5 to 2 billion people at a sustainable, decent standard of living–roughly one-third the current world population. Daily and the Ehrlichs are co-authors of a book tentatively titled “Food and Fertility: The Case for Equity,” due from Putnam next year.

Q: What led you to write this paper?

A: We believe people have to start debating the issue of optimum population size. So we proposed a set of our own personal criteria and calculated from that basis. We came up with 1.5 to 2 billion people, which was the world population from 1900 to about 1930. The figure is low because we want to give everybody a decent life. That’s one of our criteria. And because we want to ensure a long bright future for humanity, instead of the quick blip in the history of the earth we’re in danger of becoming. But we also assume the use of technologies that would be less environmentally destructive, which allows for more people.

Q: What do you mean by “a decent life?”

A: The type of lifestyle we envisioned would be considered a high standard of living in most parts of the world, roughly equivalent to France’s or Sweden’s today, but it would also be one that maintains stretches of wilderness and allow other species to persist. The criteria are not scientific. That’s a social issue. But once you’ve established what kind of life people would want to lead, you can calculate how many people the earth can sustain at that level.

Q: What makes you say that there are already more people than the earth can support?

A: In order for humanity to persist on the planet we have to use resources at a sustainable rate. Instead, we’re exhausting critical and irreplaceable resources–fertile soils, fresh water, biodiversity. The global population is over 5.6 billion, and we’re adding 90 million people each year. The UN’s median projection is for 8.4 billion people by the year 2025, but nobody knows how high we can go without a dramatic increase in the death rate from famine, disease, or some combination of humanity’s standard plagues.

One big worry is that we won’t be able to increase food production quickly enough or increase it sustainably. Already, since the end of World War II, we’ve degraded about a third of the earth’s vegetated surface trying to feed the people we have. And since 1970, over 250 million people–almost the population of the United Statesahave died of hunger. The rate of increase in food production is lagging behind the rate of increase in population in many parts of the world, and the total crop area is shrinking, by 5 percent since 1981. An area the size of Colorado is abandoned each year because it’s no longer viable to farm.

A lot of people say the real problem is distribution, that the food surpluses in the rich nations could feed the world. But in reality–and here come the numbers [from research by Robert Kates]–if you take the world’s food supply and divide it equally, giving everybody a minimal diet of 2,350 calories a day, and if everyone is a vegetarian, you could support 6 billion people. If we raise that to the equivalent of a relatively good SouthAmerican diet, with about 15 percent of calories coming from animal products, you could feed 4 billion. At a North American standard, with about 35 percent coming from animals, you could only feed 2.5 billion.

Q: Critics say that there are vast tracts of unused land.

A: That’s ridiculous. We struggle to find areas to study the functioning of natural systems, and it’s impossible to find one square centimeter that hasn’t been impacted by humans. Personally, I’ve been unable to escape cows. Even Colorado wilderness areas above 10,000 feet have cows all over them. It’s cows or condos. One of my sites in Costa Rica is even named Vaca Vaca.

This mistake is so common it even has a name–the Netherlands Fallacy: Why can’t we maintain Holland’s high population density and high standard of living across the whole planet? You have to look at the ecological footprint, how much land is required to support a single Dutch person. Just taking food, forestry products, and energy–not counting the tons of other stuff it imports–the Netherlands uses an area over 17 times its size. One study has determined that if everyone on earth lived like the average Canadian, it would take two additional earths to supply the needed resources.

Q: Other critics put their faith in the free market.

A: They say that we should let the invisible hand of the free market control prices, that as resources become scarcer their prices will go up, inducing more efficient use. Which sometimes happens. Economists often assume that the most efficient use of resources is to exhaust them sequentially, but that assumes an infinite array of resource alternatives–which we just don’t have, especially when we’re talking about soil or fresh water. Or fisheries. We’re progressively eliminating all the major fisheries. What we used to throw out we’re now consuming as the primary resource. Goodbye, salmon. Goodbye, tuna. Hello, fake crab.

Q: How can we begin to reverse the population boom?

A: In the past, family planning has focused too much on the symptoms and ignored the causes of overpopulation and environmental deterioration. One of the most optimistic things to come out of the Cairo conference is that they’ve finally gotten away from throwing condoms at women.

One critical element of any solution is social and economic equity at just about every level. There’s a lot of empirical evidence that sexual equity within the household is critical to lowering fertility rates. As it stands, it’s in poor families’ best interest to have a lot of children. One way to reverse that is to give women access to employment outside the home, which also means access to education, health care, and basic civil rights.

It’s important to understand that the population problem is not centered in poor nations. A lot of it is centered right here. Not only are we the world’s third largest nation, with the highest per capita resource consumption rates, but we have the economic and political power to impose conditions that perpetuate the vicious cycle of poverty, population growth, and environmental deterioration in other countries.

Q: What can people do?

A: The most important thing is to have no more than two children. I think that’s ethically imperative, especially in this country. The average American baby will grow up to have 30 times the impact on the environment as a baby born in Bangladesh. The second thing, I’d say, is to follow the guidelines in all those books telling you how to recycle and minimize your consumption and production of waste. Third is to create a political climate conducive to moving toward a sustainable economy.

I think people have a responsibility to educate themselves on the issues. Like this Netherlands Fallacy: it’s appalling to see it come up every time population issues are discussed. We don’t have time to operate on a kindergarten level. The longer we wait to do something, the more our options are foreclosed.

This is one of a continuing series of MoJo articles on population issues. Join the debate: E-mail to Reach Gretchen Daily by fax at the Center for Conservation Biology: (415) 723-5920.


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