Planet of the Plants

By Glenn Scherer, Grist.org. Posted July 25, 2005.

Humanity is on the threshold of a century of extraordinary bounty, courtesy of global climate change. That's the opinion of Robert Balling, former scientific adviser to the Greening Earth Society, a lobbying arm of the power industry founded by the Western Fuels Association. In a world where atmospheric carbon dioxide levels soar from the burning of fossil fuels, he says, "crops will grow faster, larger, more water-use efficient, and more resistant to stress." Quoting study after study, he invokes visions of massive melon yields, heftier potatoes, and "pumped-up pastureland." Bumper crops of wheat and rice, he says, will benefit the world's farmers and the hungry.

Balling's assertions are backed by solid science: Gaseous CO2 fertilization does cause remarkable growth spurts in many plants, and could create a greener planet with beefier tomatoes and faster-growing, bigger trees. But there's a catch: The insects, mammals, and impoverished people in developing countries who feed on this bounty may end up malnourished, or even starving.

A small but growing body of research is finding that elevated levels of atmospheric carbon dioxide, while increasing crop yield, decrease the nutritional value of plants. More than a hundred studies, for example, have found that when CO2 from fossil-fuel burning builds up in plant tissues, nitrogen (essential for making protein) declines. A smaller number of studies hint at another troubling impact: As atmospheric CO2 levels go up, trace elements in plants (such as zinc and iron, which are vital to animal and human life) go down, potentially malnourishing all those that subsist on the plants. This preliminary research has given scientists reason to worry about bigger unknowns: Virtually no studies have been done on the effects of elevated CO2 on other essential trace elements, such as selenium, an important antioxidant, or chromium, which is believed to regulate blood-sugar levels.

The less-nutritious plants of a CO2-enriched world will likely not be a problem for rich nations, where "super-sized" meals and vitamin supplements are a dietary mainstay. But things could be very different in the developing world, where millions already live on the edge of starvation, and where the micronutrient deficit, known as "hidden hunger," is already considered one of the world's leading health problems by the United Nations.

The problem of hidden hunger grew out of the 1960s "green revolution." That boom in agriculture relied on new varieties of high-yield crops and chemical fertilizers to staunch world hunger by upping caloric intake in the developing world. Unfortunately, those high-yield crops are typically low in micronutrients, and eating them has resulted in an epidemic of hidden hunger. At least a third of the world is already lacking in some chemical element, according to the U.N., and the problem is due in part to a steady diet of micronutrient-deficient green-revolution plants. Iron deficiency alone, which can cause cognitive impairment in children and increase the rate of stillbirths, affects some 4.5 billion people. Lack of iodine, another micronutrient, can result in brain damage and is a serious problem in 130 countries. According to the World Bank, hidden hunger is one of the most important causes of slowed economic development in the Third World.

Enter rising CO2 levels, which could exacerbate hidden hunger in this century. Current concentrations of atmospheric CO2 now exceed anything seen in the last 420,000 years -- and likely in the last 20 million years, according to the U.N. Intergovernmental Panel on Climate Change. And forecasts call for CO2 levels to rise dramatically, from today's 378 parts per million to 560 parts per million or more by as early as 2050. The micronutrient decline brought by these ballooning CO2 levels could collide dangerously with the developing world's nutrient-poor green-revolution crops and its exploding population. Scientists also worry about how plant nutrient deficiencies might destabilize the world's wild ecosystems in unexpected ways.

"This is one of those slow-motion effects that does not hit us like a hammer, so we don't notice it," says Irakli Loladze, an assistant professor at the University of Nebraska. But, he says, failing to notice the hidden hunger fueled by changing CO2 levels does not lessen its potential impact: "The structure of the whole food web could change."

Diet for a Nitrogen-Deprived Planet

Early carbon-dioxide enrichment experiments were relatively simple: All kinds of wild and cultivated plants were exposed in field or lab to current, doubled, and tripled levels of CO2, and scientists watched what happened. In more than 2,700 studies, plant growth typically exploded. Doubled CO2 levels resulted in an average increase in agricultural yield of over 40 percent.

Glenn Scherer is an author and freelance journalist and the former editor of Blue Ridge Press, a syndicated environmental commentary service in the Southeast.

Liked this story? Get top stories in your inbox each week from Environment! Sign up now »