Climate and Food Supply

Cynthia Rosenzweig

On April 18th, the National Climate Seminar hosted a conversation on “Climate and Food Supply” with Cynthia Rosenzweig, leader of the Climate Impacts Group at the Goddard Institute for Space Studies at Columbia University. Rosenzweig’s work has focused on the effects of climate change on systems and sectors that are important to human well-being, including agriculture and food supply. Download the accompanying slides for Rosenzweig’s talk.

While climate change research initially focused on increasing mean temperatures and precipitation, current research has now shifted to focus on extreme climate events such as heat waves and floods that have the potential to significantly affect the production and distribution of the world’s food supply. Rosenzweig explained how agriculture is particularly affected by extreme events such as heat that not only stresses crops, but also livestock, due to warmer temperatures and decreasing water availability during drought conditions. Crop yields, milk production and livestock reproduction often suffer under these conditions.

Satellite image of "2002 African fires" Credit: NASA

Climate variability and change not only has physiological effects on crops, but also increases the risk of fire and creates new opportunities for pests and pathogens. Current climate trends have been shown to affect rice yields, decrease productivity of livestock in East Asia, and require earlier planting of spring crops. Peer-reviewed literature around the world is now documenting these trends (Lobell et al.).

Credit: Texas A&M

Rosenzweig highlighted the fact that we must be careful not to attribute any singular extreme event to climate change. However, the frequency of extreme events–such as the droughts seen in the Southwest, Australia, Somalia, Ethiopia, and Djibouti–is predicted to increase. At the other extreme, it is also predicted that large downpours and floods will increase in intensity and frequency. While it is important to remember that increased levels of carbon dioxide and low level warming increase crop productivity, all else being equal, higher levels of warming decrease crop productivity. Rosenzweig noted that where this inflection point lies is still a focus of research.

In March, the IPCC released a Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX). Both the summary for policymakers and the full report are available online. From the IPCC Fact Sheet: “This IPCC report addresses, for the first time, how integrating expertise in climate science, disaster risk management, and adaptation can inform discussions on how to reduce and manage the risks of extreme events and disasters in a changing climate.”

So what do we do to prepare for these predicted extreme events?

Forests in Brazil have been cut down to make way for crops such as soya. Credit: Rodrigo Baleia/Greenpeace

Rosenzweig highlighted the need for more integrated pest management to deal with new threats from insects, diseases, and weeds. In term of climate change mitigation, since agriculture is a significant source of greenhouse gas emissions, steps must be taken to reduce the emissions of carbon dioxide, methane and nitrous oxide due to agriculture. With global population projected to rise, we must increase the food supply while eliminating deforestation of tropical forests for agriculture, reducing N2O emissions from fertilizer application, increasing the efficiency of industrial farming, and reducing methane emissions from rice paddies and ruminants.

Rosenzweig noted that farmers are already adapting to the new climate reality by adjusting planting dates and planting strains of more drought resistant crops. Other forms of adaptation include research and development to produce drought resistant and pest resistant crop strains. Along with these transformational changes in agriculture, we will need to see transformational changes in the way we live (think vegetarian!).

The effects of climate change and extreme climate events have the potential to spillover into sociopolitical situations. Negative agricultural outcomes have the potential to lead to unrest and instability in many countries. In this vain, Rosenzweig and colleagues are developing integrated models that include climate predictions, crop simulations and economic factors to improve agricultural practices, adaptation, and outcomes in developing countries as part of the Agricultural Model Intercomparison and Improvement Project (AgMIP).

AgMIP Global Workshop

Teams of agricultural researchers from different world regions are responsible for running simulation models to determine potential areas of concern. Rosenzweig stressed the importance for integrated agricultural policy across the spectrum of international, regional, and national governments to transform and adapt agricultural practices in the face of the risks posed by climate change.

Join the National Climate Seminar on May 2nd for the last conversation of the semester entitled “Carbon Supply Chain: Black Mesa and Beyond” with Jihan Gearon, Director of the Black Mesa Coalition. Call in at noon eastern on May 2nd to join the conversation with Jihan Gearon! Call-in number: 1-712-432-3100; Conference Code: 253385. Send advance questions for Jihan to Or, listen to podcasts of the conversation with Cynthia Rosenzweig and of previous NCS conversations.

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