Overpopulation panic is back. Concerns about a world too full of "filthy human children" motivated eco-terrorist James Lee when he held employees of the Discovery Channel hostage at gunpoint in September. But the deranged Lee is far from alone when it comes to worrying about overpopulation. The May-June cover of the progressive magazine Mother Jones asked, "Who's to Blame for the Population Crisis?" British journalist Matthew Parris wrote an op-ed in September in the London Times asserting, "If you want to save the planet, stop breeding." Parris further coyly suggested that we study "China's example, for lessons good and bad."

But on World Population Day in July, British journalist Fred Pearce argued that "population is not the problem." Pearce's relatively sanguine article at the environmentalist website Grist provoked Robert Walker, former head of the anti-gun group Handgun Control and now executive vice-president of the Population Institute, to respond at the same site with an article titled "Of course population is still a problem."

Walker asks Pearce what he evidently thinks are deep questions: "Looking ahead, Fred, will these countries [with anticipated population growth in Africa and Asia] be able to feed themselves? Will they have enough safe drinking water? Will their lands be deforested or their rivers polluted? Will their maternal mortality rates and infant mortality rates remain unacceptably high? Will they be caught in a demographic poverty trap? Will they become failed states? If you have good answers to these questions, please let me know."

Let's take a stab at providing good answers to Walker's questions.

Will the world be able to feed itself in 2050? As it happens, the journal Philosophical Transactions of the Royal Society B (Biological Sciences) devoted its September 27 issue to analyzing the issue of global food security through 2050. One of the specially commissioned research articles projects that world population will reach around 9 billion by 2050 and that in the second half of the 21st century, "population stabilization and the onset of a decline are likely." This should allay Ryerson's concern that the world's resources are not infinite and therefore "cannot support an infinite population of humans." So okay, infinite human population growth isn't likely, but can the Earth adequately feed 9 billion people by 2050?

Well, yes, suggest two other of the Royal Society articles. A review of the relevant scientific literature led by Keith Jaggard from Rothamsted Research looks at the effects of climate change, CO2 increases, ozone pollution, higher average temperatures, and other factors on future crop production. Jaggard and his colleagues conclude [PDF], "So long as plant breeding efforts are not hampered and modern agricultural technology continues to be available to farmers, it should be possible to produce yield increases that are large enough to meet some of the predictions of world food needs, even without having to devote more land to arable agriculture."

Applying modern agricultural technologies more widely would go a long way toward boosting yields. For example, University of Minnesota biologist Ronald Phillips points out that India produces 31 bushels of corn per acre now which is at the same point U.S. yields were in the 1930s. Similarly, South Africa produces 40 bushels (U.S. 1940s yields); Brazil 58 bushels (U.S. 1950s yields); China 85 bushels (U.S. 1960s yields). Today's modern biotech hybrids regularly produce more than 160 bushels of corn per acre in the Midwest. For what it's worth, the corporate agriculture giant Monsanto is aiming to double yields on corn, soybeans, and cotton by 2030. Whether or not specific countries will be able to feed themselves has less to do with their population growth than it does with whether they adopt policies that retard their economic growth.

Another article looking at the role of agricultural research and development finds that crop yields have been recently increasing at about 1 percent per year. In that article researchers estimate that spending an additional $5 to $10 billion per year would increase food output by 70 percent over the next 40 years. Note that world population is expected to increase by about 33 percent over that period.

What about safe drinking water? Water is more problematic. The researchers commissioned by the Royal Society run a model that projects that competition for water to meet environmental flow requirements (EFRs) and municipal and industrial demand will "cause an 18 percent reduction if the availability of water worldwide for agriculture by 2050." Interestingly, the amount of freshwater withdrawn for municipal and industrial use was 4.3 percent in 2000 and is estimated to increase to 5.9 percent by 2050. So the main competition for agricultural water is maintaining flows for environmental reasons. Since water is now often unpriced and subsidized, it gets used very inefficiently. As water becomes scarcer farmers and other users will have incentives to adopt water sparing techniques, such as drip irrigation. In addition, researchers are close to developing drought tolerant crops. The study also notes that water stressed regions will be able to "import water" in the form of food produced in areas with abundant water.

With regard to deforestation and polluted rivers, the answer is probably yes for many of the poorest countries. However, speeding up economic growth and technological improvements will dramatically lower the risks of these undesirable outcomes. As noted above, enough food to feed 9 billion can be grown on land currently devoted to agriculture. With regard to water pollution, it is one of the first environmental problems that poor countries begin to clean up as they grow wealthier. A recent study found that in every country where average annual per capita income exceeds $4,600 forests are stable or increasing [PDF]. In addition, technological progress offers the possibility that humanity will increasingly reduce its future demands on nature by a process of dematerialization [PDF], that is, obtaining more value while using less material.

Maternal mortality rates have fallen substantially—from 422 per 100,000 live births to 251 per 100,000 live births—over the past 30 years, according to a study published in The Lancet this past April. Sadly, the study noted, "More than 50% of all maternal deaths were in only six countries in 2008 (India, Nigeria, Pakistan, Afghanistan, Ethiopia, and the Democratic Republic of the Congo)." Oddly, some activists opposed the publication of The Lancet article, fearing that the good news would stifle their fundraising. The world's infant mortality rate has never been lower. Most countries, even very poor countries, continue to experience declines in infant mortality.

Walker's last two questions about poverty traps and failed states are related, but not in a way that supports his implied points. As Wheaton College economist Seth Norton explains, "Fertility rate is highest for those countries that have little economic freedom and little respect for the rule of law." He adds, "The relationship is a powerful one. Fertility rates are more than twice as high in countries with low levels of economic freedom and the rule of law compared to countries with high levels of those measures."

Fertility rates are high in failed states like Somalia, Chad, Sudan, Pakistan, Nigeria, and Yemen, because of the lack of rule of law which inexorably generates poverty. Norton persuasively argues that such places are so chaotic that it's like living in giant open access commons. In those cases people often reason that more children means more hands for grabbing unowned and unprotected resources for the family. Such anarchic places would be particularly ill-suited to implementing the kind of population control policies Walker favors.

According to research published by the Royal Society, it looks as though the world will be able to feed 9 billion people by 2050, perhaps even allowing some farmland to revert to nature. Water is a problem, but economic and technological solutions show promise in ameliorating it. But more importantly, Walker and other overpopulationists get the causality backwards. Poverty is the cause and high fertility is the symptom. Poverty traps and failed states which result in high maternal death rates, starvation, pollution, and deforestation are not created by population, but by bad policies. Working to spread economic freedom and political liberty is a lot harder than self-righteously blaming poor people for breeding too much. But it's the only real option.

Ronald Bailey is Reason's science correspondent. His book Liberation Biology: The Scientific and Moral Case for the Biotech Revolution is now available from Prometheus Books.