GLOBAL KNOWLEDGE FOR GLOBAL CHANGE

Declining crop yields and increasing food prices? Modelling the effects of climate change on agriculture

17 December 2013

Meeting the world's growing demand for food in coming decades is likely to become more difficult as already stressed agricultural systems will be challenged by population growth and rising income in some of the world's poorest regions. Climate change will exacerbate the challenges in many dimensions. Are the effects of climate change more serious than other threats to sustainable food security?

Kitiona Tausi tends vegetable seedlings in his garden. The rising cost of imported food produce has led to increased interest in growing crops at home. However, land scarcity and a shortage of fresh water has limited its effectiveness. The tiny Pacific island nation is one of the few places in the world already experiencing the devastating effects of climate change and global warming. Due to the rising sea level, erosion, and extreme weather events, the island is shrinking and may eventually disappear beneath the Pacific Ocean. Credit: Jocelyn Carlin - Panos

Models that incorporate both the effects of climate change and socioeconomic changes can help to disentangle the relative consequences of a range of threats and identify potential policy interventions. Today's models that incorporate agriculture often give conflicting results. Comparisons of their results help to identify the sources of differences and provide deeper insights to aid in policy formation and programme development.

New study provides unique perspective on the effects of climate change on agriculture

A recently published paper "Climate change effects on agriculture: economic responses to biophysical shocks" in a special feature of the Proceedings of the
National Academy of Sciences of the United States of America (PNAS)
 provides a unique perspective on the effects of climate change on agriculture, viewing it through the lens of nine global economic models with climate change inputs from two general circulation models and five crop models.

IDS Fellow Dirk Willenbockel was a contributing author, and the study was coordinated by the Agricultural Model Intercomparison and Improvement Project (AgMIP).

Integrating biophysical and socioeconomic modelling

An integral part of the analysis was the close integration of biophysical with socioeconomic modeling, making it possible to assess both the direct biological effects of climate change on yields and the responses of producers, consumers, and traders. The study responds to a long-standing need for a systematic comparison of model results for agricultural futures scenarios, because past results have varied widely, due to differences in model structures and parameters, choice of scenarios, and data.

Lead author, Gerald Nelson (from the University of Illinois), said, "This is the first time that this many of the world's leading global models with significant representation of agriculture have worked together to understand where their results are similar, where they differ, and importantly, why they differ."

He added "The future is uncertain, but understanding what the world's leading modellers think about how agricultural producers, food consumers, and international trade flows will respond provides valuable guidance to both the public and private sectors as they think about policy changes and investment priorities."

Decline in crop yields and increase in food prices

Findings from the analysis include the following (all figures compare 2050 forecasts with and without climate change):

  • The average direct climate change effect on crop yields is a 17 percent decline, but with significant differences by crop, region, and crop and climate models
  • The final average yield effect is an 11 percent decline as farmers respond by altering input use and management practices on existing agricultural area, expanding production into new areas (an increase in area globally of about 8 percent) and reduced consumption (a decline of about 3 percent)
  • The average effect on crop prices is a 20 percent increase, but for some crops in some regions prices don't change at all, while in others the increase is over 60 percent
  • Differences in model results arise from different assumptions made by the modelling groups in three areas: How easy is it to convert nonagricultural land to cropping? How much can farmers respond to higher prices with higher yields? And how much can international trade flows respond to the different regional climate effects?

The special PNAS feature assembles the first results of the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP) which aims to bring research on climate impacts onto a new level, by providing a framework to collate a consistent set of impact data across a number sectors and scales. The ISI-MIP team is coordinated by the Potsdam Institute for Climate Impact Research in Germany and the International Institute for Applied Systems Analysis in Austria, and involves two-dozen research groups from eight countries.

Further ISI-MIP results are published online by PNAS