Global Warming Effects Around the World

Yirga Chefe, Ethiopia

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Farm worker in Ethiopia

Coffee production is a critical component of Ethiopia's economy. Rising temperatures are threatening the nation's coffee crops by enabling infestations of insect pests that decrease the quality and yield of coffee berries.1

Key Facts

Ethiopia is the birthplace of Arabica coffee. As the seventh-largest coffee producer in 2006, the nation is a critical contributor to the global coffee market.2 Yet warming temperatures combined with past declines in world coffee prices are threatening Ethiopia's crop, increasing the vulnerability of 700,000 families that depend on coffee for their livelihood.4

  • From 1979 to 2005, the Ethiopian highlands saw a warming of 0.70 to 1.17° F (0.39 to 0.65° C).5
  • Rising temperatures have caused widespread infestations of the coffee berry borer beetle,9 a pest that causes annual losses of roughly $500 million—and affects the income of more than 20 million households worldwide.4,
  • From 2002 to 2009, Ethiopian coffee yields declined by nearly 35 percent.13 Mid–range scenarios20 for future heat-trapping emissions–primarily from the burning of oil, gas, and trees—project a warming of 5.4 to 6.3° F (3.0-3.5° C) by 2100.14,19 That warming will likely exacerbate the environmental challenges already stressing Ethiopia's vulnerable coffee growers.9


Arabica coffee has its origins in the highlands of Ethiopia, where it still grows naturally in forests. The Ethiopian economy depends heavily on coffee production. Coffee exports accounted for 21 percent of the country's export income in coffee in 2010, compared with an average of 65 percent in the 1990s, before a global decline in coffee prices.3

More than 700,000 families in Ethiopia work in coffee production.4 Agriculture accounts for 85 percent of the nation's total employment, and 45 percent of GDP.3 Warming temperatures, combined with past declines in world coffee prices, are threatening Ethiopia's coffee industry–a serious concern, given its importance to the nation's economy.

From 1979 to 2005, the Ethiopian highlands saw a warming of about 0.70–1.17° F (0.39–0.65° C).5 Coffee's preferred temperature range is fairly narrow–64–71° F (18–22° C): both yield and quality decline above or below that range.6 Above 93° F (34° C), little photosynthesis occurs within the coffee plant.7

Besides affecting the growth of coffee plants, warmer temperatures are also expanding the range of one of the world's most significant coffee pests: the coffee berry borer.8,9 These beetles bore into coffee berries to lay their eggs. The hatched larvae feed on the berry seeds, reducing the yield and quality of the crops.9 On a global basis, the coffee berry borer causes losses of around $500 million annually, and affects the income of more than 20 million households.4

Before 1984, temperatures in the Ethiopian highland's coffee–growing regions were cool enough to keep the coffee berry borer in check. Since 1984, however, rising temperatures have enabled several generations of beetles per coffee season.9 While surveys in 1967 did not show any evidence of coffee berry borers, those conducted in 2003 found that the beetle was widespread in southwestern Ethiopia.11,12

The rise in temperatures and infestation of coffee berry borers may already be affecting Ethiopian coffee crops. From 2002 to 2009, coffee yields plunged by nearly 35 percent.13

Arabica coffee plants are also highly sensitive to rainfall.6 Coffee flower buds need two–to four–month dry periods to form, and the development of leaves and fruit coincides with the beginning of the rainy season.6,7 When rainfall is abundant throughout the year, or when there is no dry period, coffee yields tend to be low.6 While Ethiopia has so far shown little evidence of any trend in extreme precipitation events, the country's agriculture is sensitive to major droughts, as evidenced by famines in the 1980s.14

Part of a Larger Pattern

On a global basis, changes in climate since the 1950s have contributed to more frequent extreme rainfall events.15 Because temperature and the timing and amount of rainfall can affect coffee plants directly, by making growing conditions less optimal, and indirectly, by enabling the success of pests such as the coffee berry borer, coffee–growing regions throughout the world are susceptible to changes in climate.

In the coffee–growing Cauca region of Colombia, for example, declines in coffee production have been attributed to a combination of rising temperatures and more frequent extreme rainfall events.16 These changes have fostered the regional growth of coffee rust, a fungal pest that can cause plants to drop their leaves too early in the season.16

These climate–related threats to coffee are occurring against a backdrop of global volatility in the coffee market. The collapse of the International Coffee Agreement in 1988 and 1989 led to an oversupply of coffee on world markets, and a subsequent drop in prices.16 Coffee prices dropped to a 30–year low in 2002, threatening the livelihoods of coffee workers around the world.18 Attempts to stabilize prices or develop new international trade agreements have not occurred as of 2005.17

What the Future Holds

Because our continued burning of oil, gas, and trees means our heat–trapping emissions are rising, temperatures in East Africa are projected to continue to increase over the course of this century.14,19 A mid-range emissions scenario20 projects a 5.4–6.3° F (3.0–3.5° C) warming by 2100.14,19 East Africa is also projected to see an increase in rainfall14,19 and coffee berry borer populations9 as climate change continues. These changes will likely add to the stresses already facing Ethiopian coffee growers.

Adaptations such as diversifying crops17—and using recent information on climate variability to develop long–term plans for managing them—may help reduce the vulnerability of Ethiopian coffee growers to continued changes in temperature and rainfall.



  1. Photo: Image used with permission from Technoserv. Accessed online June 17, 2011 at
  2. Petit, N. 2007. Ethiopia's coffee sector: A bitter or better future? Journal of Agrarian Change 7(2):225–263.
  3. CIA. 2011. World factbook. Washington, DC. Online at
  4. Vega, F.E., E. Rosenquist, and W. Collins. 2003. Global project needed to tackle coffee crisis. Nature 425:343.
  5. Trenberth, K.E., P.D. Jones, P. Ambenje, R. Bojariu, D. Easterling, A. Klein Tank, D. Parker, F. Rahimzadeh, J.A. Renwick, M. Rusticucci, B. Soden, and P. Zhai. 2007. Observations: Surface and atmospheric climate change. In: Climate change 2007: The physical science basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. Miller. Cambridge, UK, and New York, NY, USA: Cambridge University Press.
  6. DaMatta, F.M., and J.D. Cochico Ramalho. 2006. Impacts of drought and temperature stress on coffee physiology and production: A review. Brazilian Journal of Plant Physiology 18(1):55–81.
  7. Lin, B.B., I. Perfecto, and J. Vandermeer. 2008. Synergies between agricultural intensification and climate change could created surprising vulnerabilities for crops. BioScience 58(9):847–854.
  8. Damon, A. 2000. A review of the biology and control of the coffee berry borer, Hypothenemus hampei (Coleoptera: Scolytidae). Bulletin of Entomological Research 90:453–465.
  9. Jaramillo, J. A. Chabi–Olaye, C. Kamonjo, A. Jaramillo, F.E. Vega, H.–M. Poehling, and C. Borgemeister. 2009. Thermal tolerance of the coffee berry borer (Hypothenemus hampei): Predictions of climate change impact on a tropical insect pest. PLoS ONE 4(8):e6487. doi:10.137/journal.pone.0006487.
  10. Vega, F.E., F. Infante, A. Castillo, and J. Jaramillo. 2009. The coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae): A short review, with recent findings and future research directions. Terrestrial Arthropod Reviews 2:129–147.
  11. Davidson, A. 1967. The occurrence of coffee berry borer Hypothenemus (Stephanoderis) hampei in Ethiopia. Cafß 8:1–3.
  12. Mendesil E., B. Jembere, and E. Seyoum. 2003. Occurrence of coffee berry borer Hypothenemus hampei (Ferrari) (Coleoptera: Scolytidae) on Coffea arabica L. in Ethiopia. Ethiopian Journal of Biological Sciences 2:61–72.
  13. Food and Agriculture Organization of the United Nations. FAOSTAT data for 1993–2009. Rome, Italy. Online at
  14. Conway, D., and E.L.F. Schipper. 2011. Adaptation to climate change in Africa: Challenges and opportunities identified from Ethiopia. Global Environmental Change 21:227–237.
  15. Min, S–K., X. Zhang, F.W. Zwiers, and G.C. Hegerl. 2011. Human contribution to more–intense precipitation extremes. Nature 470:378–381.
  16. Rosenthal, E. 2011. Heat damages Colombia coffee, raising prices. New York Times, March 9. Online at
  17. Amsalu, A., and E. Ludi. 2010. The effect of global coffee price changes on rural livelihoods and natural resource management in Ethiopia: A case study from Jimma area. Bern, Switzerland: NCCR North-South Dialogue 26.
  18. Daniels, S. and S. Petchers. 2005. The coffee crisis continues: Situation assessment and policy recommendations for reducing poverty in the coffee sector. Boston, MA, USA: Oxfam America. Online at
  19. Christensen, J.H., B. Hewitson, A. Busuioc, A. Chen, X. Gao, I. Held, R. Jones, R.K. Kolli, W.–T. Kwon, R. Laprise, V. Magañ:a Rueda, L. Mearns, C.G. Menéndez, J. Räisänen, A. Rinke, A. Sarr, and P. Whetton. 2007. Regional climate projections. In: Climate change 2007: The physical science basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. Miller. Cambridge, UK, and New York, NY, USA: Cambridge University Press.
  20. The scenario referred to here is the middle-emissions pathway known as A1B from the Intergovernmental Panel on Climate Change.
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