Agriculture in a Warmer World

March 7, 2008

EarthLast week, CUESA hosted a lecture about global climate change and agriculture. Dr. W. Michael Hanemann of the California Climate Change Center at UC Berkeley and Dr. David Lobell of  Stanford University’s Program on Food Security and the Environment shared their perspectives on how climate change might impact food supply, food distribution, and food security in the Bay Area and around the world. This week, we offer a brief summary of some of the information they presented. You can download an mp3 of the talk here.

Since the advent of the industrial revolution, human activities have been increasing the concentration of greenhouse gases in Earth’s atmosphere. The resulting rise in global temperatures is already changing our environment and culture, and will become more perceptible as we advance further into the 21st century. Even if humans stop producing greenhouse gases today, we will continue to experience the consequences of our past emissions for at least another 25 years; our current emissions will determine the degree to which global warming affects us beyond that. If we make drastic successful efforts to curb the release of gases like carbon dioxide (CO2) and methane, global temperatures might rise by an average of three or four degrees Celsius by the end of this century; if we continue business as usual, an average increase of more than ten degrees is possible.

While higher temperatures could lead to increased agricultural productivity in cooler parts of the world, the overall effect of a warmer climate on the global harvest, say both Hanemann and Lobell, will be negative. When temperatures increase past a certain point, plant productivity declines precipitously. As well, an expected increase in major weather events because of warming will lead to more frequent wholesale crop losses.

Some factors will lessen the impacts of climate change. Higher atmospheric CO2 levels have a fertilizing effect, and could at least partially offset losses in plant productivity. The ingenuity of farmers and scientists will also help agriculture adapt to temperature increases. These factors, however, are unlikely to fully mitigate the effects of climate change on agriculture. New crop varieties, tools, techniques and partnerships will undoubtedly be important, but adaptation can be slow and costly.

Adaptive measures, says Dr. Lobell, are likely to come less quickly in the countries that need them most. The majority of the world’s less economically developed nations also happen to be in warmer regions of the Earth, where climate change will wreak the most havoc. “This,” says Dr. Lobell, “is one of the great ironies of climate change… the folks who cause the most warming are the ones who are hurt the least.”

In California, though, we might face our fair share of warming worries. Rising sea levels could threaten coastal agriculture. Warming could cause an increase in agricultural pests. Perhaps most alarmingly, water for agriculture could become much more scarce. Says Dr. Hanemann, “California is a story of mismatch. The precipitation occurs in the northern part of the state… the people live south of there. The timing is wrong: three quarters of all the water in California is used between April and September, but only 20% of the precipitation occurs then.” As a result, we rely on snow pack for about a third of our dry-season water supply. Higher temperatures mean less snow and quicker snowmelt, and therefore less water. Higher temperatures also mean increased demand, because plants will need more water to stay alive. If California is to maintain its level of agricultural production, costly catchment and reservoir projects, major conservation measures, and new crop varieties will be necessary.

The good news is that California is doing more than any other state to lessen its significant contributions to climate change. Since 1997, the state has been consistently funding research and implementing legislation to moderate our impact on the climate.

While legislation and science will play a big role in solving the problems of global warming, so too will the actions of individuals. Agriculture is both affected by and affects global warming. One of the ways to lessen our impact is through our food choices. Please join CUESA for the second lecture in our global climate change and agriculture series on March 31, and find out how you can make cooler food choices.


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