Warming of the Indian Ocean threatens eastern and southern African food security but could be mitigated by agricultural development

doi:10.1073/pnas.0708196105

Warming of the Indian Ocean threatens eastern and southern African food security but could be mitigated by agricultural development

*United States Geological Survey, Geography Department, University of California, Santa Barbara, CA 93106-1120;
^‡United States Geological Survey, Scripps Institution of Oceanography, La Jolla, CA 92093-0224;
^§United States Geological Survey, Center for Earth Resources Observation and Science, SD 57198-0001;
^¶Science Systems and Applications, Code 614.4, National Aeronautics and Space Administration–Goddard Space Flight Center, Greenbelt, MD 20771; and
^‖Environmental, Earth, and Atmospheric Sciences, University of Massachusetts, Lowell, MA 01854

Edited by Stephen H. Schneider, Stanford University, Stanford, CA, and approved May 27, 2008 (received for review August 29, 2007)

Abstract

Since 1980, the number of undernourished people in eastern and southern Africa has more than doubled. Rural development stalled and rural poverty expanded during the 1990s. Population growth remains very high, and declining per-capita agricultural capacity retards progress toward Millennium Development goals. Analyses of in situ station data and satellite observations of precipitation have identified another problematic trend: main growing-season rainfall receipts have diminished by ≈15% in food-insecure countries clustered along the western rim of the Indian Ocean. Occurring during the main growing seasons in poor countries dependent on rain-fed agriculture, these declines are societally dangerous. Will they persist or intensify? Tracing moisture deficits upstream to an anthropogenically warming Indian Ocean leads us to conclude that further rainfall declines are likely. We present analyses suggesting that warming in the central Indian Ocean disrupts onshore moisture transports, reducing continental rainfall. Thus, late 20th-century anthropogenic Indian Ocean warming has probably already produced societally dangerous climate change by creating drought and social disruption in some of the world's most fragile food economies. We quantify the potential impacts of the observed precipitation and agricultural capacity trends by modeling “millions of undernourished people” as a function of rainfall, population, cultivated area, seed, and fertilizer use. Persistence of current tendencies may result in a 50% increase in undernourished people by 2030. On the other hand, modest increases in per-capita agricultural productivity could more than offset the observed precipitation declines. Investing in agricultural development can help mitigate climate change while decreasing rural poverty and vulnerability.

Footnotes

^†To whom correspondence should be addressed at:
University of California, Geography Department, 1629 Ellison Hall, Climate Hazard Group, Santa Barbara, CA 93106-1120.
E-mail: chris{at}geog.ucsb.edu
Author contributions: C.F. designed research; C.F., M.B., and A.H. performed research; C.F., M.D.D., and M.B. contributed new reagents/analytic tools; C.F., M.E.B., and M.B. analyzed data; and C.F., M.D.D., J.C.M., J.P.V., and M.E.B. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0708196105/DCSupplemental.
↵** Please see our online SI Materials and Methods for a specific description of our methods.
↵†† Agriculture, population, food-security, and food-aid statistics were obtained from the United Nations Food and Agriculture Organization.
Freely available online through the PNAS open access option.