The impact of global warming on food prices and hunger could be large over the next 20 years, according to a new Stanford University study. Researchers say that higher temperatures could significantly reduce yields of wheat, rice and maize - dietary staples for tens of millions of poor people who subsist on less than $1 a day. The resulting crop shortages would likely cause food prices to rise and drive many into poverty.  

But even as some people are hurt, others would be helped out of poverty, says Stanford agricultural scientist David Lobell.

Lobell discussed the results of his research on Feb 19 at the annual meeting of the American Association for the Advancement of Science in San Diego.

"Poverty impacts depend not only on food prices but also on the earnings of the poor," said Lobell, a center fellow at Stanford's Program on Food Security and the Environment (FSE). "Most projections assume that if prices go up, the amount of poverty in the world also will go up, because poor people spend a lot of their money on food. But poor people are pretty diverse. There are those who farm their own land and would actually benefit from higher crop prices, and there are rural wage laborers and people that live in cities who definiztely will be hurt."

Lobell and his colleagues recently conducted the first in-depth study showing how different climate scenarios could affect incomes of farmers and laborers in developing countries.

Household incomes

In the study, Lobell, former FSE researcher Marshall Burke and Purdue University agricultural economist Thomas Hertel focused on 15 developing countries in Asia, Africa and Latin America. Hertel has developed a global trade model that closely tracks the consumption and production of rice, wheat and maize on a country-by-country basis. The model was used to project the effects of climate change on agriculture within 20 years and the resulting impact on prices and poverty.

Using a range of global warming forecasts, the researchers were able to project three different crop-yield scenarios by 2030:

• "Low-yield" - crop production is toward the low end of expectations.
• "Most likely" - projected yields are consistent with expectations.
• "High-yield" - production is higher than expected.

"One of the limitations of previous forecasts is that they don't consider the full range of uncertainties - that is, the chance that things could be better or worse than we expect," Lobell said. "We provided Tom those three scenarios of what climate change could mean for agricultural productivity. Then he used the trade model to project how each scenario would affect prices and poverty over the next 20 years.

"The impacts we're talking about are mainly driven by warmer temperatures, which dry up the soil, speed up crop development and shut down biological processes, like photosynthesis, that plants rely on," he added. "Plants in general don't like it hotter, and in many climate forecasts, the temperatures projected for 2030 would be outside the range that crops prefer."

Results

The study revealed a surprising mix of winners and losers depending on the projected global temperature. The "most likely" scenario projected by the International Panel on Climate Change is that global temperatures will rise 1.8 degrees Fahrenheit (1 degree Celsius) by 2030. In that scenario, the trade model projected relatively little change in crop yields, food prices and poverty rates

But under the "low-yield" scenario, in which temperatures increase by 2.7 F (1.5 C), the model projects a 10 to 20 percent drop in agricultural productivity, which results in a 10 to 60 percent rise in the price of rice, wheat and maize. Because of these higher prices, the overall poverty rate in the 15 countries surveyed was expected to rise by 3 percent.

However, an analysis of individual countries revealed a far more complicated picture. In 11 of the 15 countries, poor people who owned their own land and raised their own crops actually benefited from higher food prices, according to the model. In Thailand, for example, the poverty rate for people in the non-agricultural sector was projected to rise 5 percent, while the rate for self-employed farmers dropped more than 30 percent - in part because, as food supplies dwindled, the global demand for higher-priced crops increased.

"If prices go up and you're tied to international markets, you could be lifted out of poverty quite considerably," Lobell explained. "But there are a lot of countries, like Bangladesh, where poor people are either in urban areas or in rural areas but don't own their own land. Countries like that could be hurt quite a lot. Then there are semi-arid countries - like Zambia, Mozambique and Malawi - where even if prices go up and people own land, productivity will go down so much that it can't make up for those price increases. In the 'low-yield' scenario, those countries would see higher poverty rates across all sectors."

Under the "high-yield" scenario, in which global temperatures rise just 0.9 F (0.5 C), crop productivity increased. The resulting food surplus led to a 16 percent drop in prices, which could be detrimental to farm owners. In Thailand, the poverty rate among self-employed farmers was projected to rise 60 percent, while those in the non-agriculture sector saw a slight drop in poverty. In Zambia, Mozambique, Malawi and Uganda, poverty in the non-farming sector was projected to decline as much as 5 percent.

Risk management

Lobell said that, although the likelihood of the "low-yield" or "high-yield" scenario occurring is only 5 percent, it is important for policymakers to consider the full range of possibilities if they want to help countries adapt to climate change and ultimately prevent an increase in poverty and hunger. 

"It's like any sort of risk management or insurance program," he said. "You have to have some idea of the probability of events that have a big consequence. It's also important to keep in mind that any change, no matter how extreme, will benefit some households and hurt others."

The Program on Food Security and the Environment at Stanford is an interdisciplinary research and teaching program that generates policy solutions to the persistent problems of global hunger and environmental damage from agricultural practices worldwide. The program is jointly run by Stanford's Woods Institute for the Environment and the Freeman Spogli Institute for International Studies.

While Americans' appetite for seafood continues to grow, most of us know little about where our fish comes from or how it was produced. In California, more than half of our seafood comes from aquaculture, often imported from fish farms in other countries. Just as most chickens, pigs and cows are raised in tightly confined, intensive operations, so too are many farm-raised fish.

But raising fish in tight quarters carries some serious risks. Disease and parasites can be transmitted from farmed to wild fish. Effluents, antibiotics and other chemicals can be discharged into surrounding waters. Nonnative farmed fish can escape into wild fish habitat. And a reliance on wild-caught fish in aquaculture feed can deplete food supplies for other marine life.

These environmental impacts have been evident in many other countries with intensive marine fish farming. In Chile, where industry expansion was prioritized over environmental protection, salmon aquaculture has collapsed, causing a major blow to what had been one of Chile's leading exports. Tens of thousands of people are now jobless in southern Chile, where the salmon farming industry once boomed.

If aquaculture is to play a responsible role in the future of seafood here at home, we must ensure that the "blue revolution" in ocean fish farming does not cause harm to the oceans and the marine life they support.

In December, Rep. Lois Capps (D-Santa Barbara) introduced in the House the National Sustainable Offshore Aquaculture Act, a bill that addresses the potential threats of poorly regulated fish farming in U.S. ocean waters. Her bill shares many of the features of a California state law, the Sustainable Oceans Act, which was written by state Sen. Joe Simitian (D-Palo Alto) and signed by Gov. Arnold Schwarzenegger in 2006. That legislation regulates fish farming in state waters, which extend three miles off the California coast. At present, all aquaculture operations in California and the U.S. are located just a few miles offshore.

If the U.S. and other states follow California's lead, we may be able to reward innovation and responsibility in aquaculture and at the same time prevent the kind of boom-and-bust development that happened in Chile. Unlike previous attempts to legislate fish farming at the national level, the Capps bill would ensure that U.S. aquaculture in federal waters, which extend from three to 200 miles offshore, establishes as a priority the protection of wild fish and functional ecosystems. It would ensure that industry expansion occurs only under the oversight of strong, performance-based environmental, socioeconomic and liability standards.

The bill also would preempt ecologically risky, piecemeal regulation of ocean fish farming in different regions of the U.S. Indeed, regulation efforts are already underway in many states, with no consistent standards to govern the industry's environmental or social performance. If these piecemeal regional initiatives move forward, it will get much more difficult to create a sustainable national policy for open-ocean aquaculture.

Previous federal bills introduced in 2005 and 2007 were fundamentally flawed -- and ultimately did not pass -- because they put the goal of aquaculture expansion far above that of environmental protection. Now, for the first time, a bill has been introduced that would demonstrably protect marine ecosystems, fishing communities and seafood consumers from the risks of poorly regulated open-ocean aquaculture.

The Obama administration is currently developing a national policy to guide the development of U.S. aquaculture. The administration would do well to embrace the vision articulated by Capps and Simitian for a science-based and precautionary approach to help ensure a responsible future for U.S. ocean fish farming.

Rosamond L. Naylor is director of the program on food security and the environment at Stanford University. George H. Leonard is director of the aquaculture program at the Ocean Conservancy in Santa Cruz.

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