For agricultural interests the world over, climate change is not a dim threat, but a reality with diverse long and short-term impacts, believes Cynthia Rosenzweig.

Without the agricultural revolution of eight to 10 thousand years ago, there would be far fewer people and “we’d all be out hunting and gathering.” The food surpluses that came from cultivation of crops and domestication of livestock “allowed the development of civilization as we know it,” says Rosenzweig. Agriculture has grown into a vast and varied enterprise globally, and now contributes its fair share to global warming. Greenhouse emissions began not 200 but thousands of years ago, with the clearing of land and forests, and the intensive planting of certain crops. Today, more than a third of nitrous oxide emissions are due to fertilizer use; farm energy needs and food transportation spews out carbon dioxide; and the rise of the factory feedlot and rice plantations have given us huge increases in methane.

Citing the latest models from international research groups, Rosenzweig offers projections of the impacts of climate change on agriculture. By the end of this century, the higher latitudes should expect more precipitation, the lower latitudes less. As we “march through time getting warmer,” the increases in CO2 will initially be better for crops, because it will increase photosynthesis. Regions with short growing seasons may see them lengthened, so for instance, Finnish farmers will be pleased they can plant early spring potatoes (which fetch a premium price).

But droughts and floods will become more frequent, and the change in seasonality will put great stress on irrigation schemes and planting schedules. A single, powerful hit during a growing season can destroy a crop. And expect “weeds and critters to change in response to the changing climate,” says Rosenzweig. Pests are already expanding their ranges. Not surprisingly, the most vulnerable to these fluctuations are developing countries, where greater populations are dependent on agriculture.

Warming in the last 30 years has already begun to affect the health of food crops and their yields across the globe. Strategies for solutions must involve both mitigation to reduce long-term risk, and adaptation to current conditions, says Rosenzweig. So we must turn to biofuels and reduce CO2 and methane emissions, while figuring out how to cushion crops against drought and flood, bioengineering those that can manage higher temperatures. In this way, climate change can function as “a transformative issue by which agricultural sustainability may be achieved.”

ABOUT THE SPEAKER:
Cynthia Rosenzweig heads the Climate Impacts Group at the Goddard Institute. She has organized and led large-scale interdisciplinary regional, national, and international studies of climate change impacts and adaptation. She is a Coordinating Lead Author of the chapter on observed changes for the IPCC Working Group II Fourth Assessment Report, and served on the IPCC Task Group on Data and Scenarios for Impact and Climate Assessment (TGICA).

Rosenzweig's research involves the development of interdisciplinary methodologies by which to assess the potential impacts of and adaptations to global environmental change. A recipient of a Guggenheim Fellowship, she has joined impact models with global and regional climate models to predict future outcomes of both land-based and urban systems under altered climate conditions. She is a Professor of Environmental Science at Barnard College and a Senior Research Scientist at the Columbia Earth Institute.

Rosenzweig received a B.S.in Agricultural Sciences, 1980, from Cook College; an M.S. in Soils and Crops, 1983, from Rutgers University; and a Ph.D.in Plant, Soil and Environmental Sciences, in 1991, from the University of Massachusetts, Amherst.