While the full impact of climate change has yet to be felt, agencies such as NASA, the EPA, and NOAA have chronicled its initial effects over the last 30 years. In addition to rising sea levels and shrinking glaciers, evidence includes modifications in species habitats. Coral suffer as temperatures rise, while other less welcome species can flourish.

Among global warming’s unwanted beneficiaries is the coffee berry borer (Hypothenemus hampei), which feeds on the bean of the coffee plant. The most significant coffee pest worldwide, H. hampei already impacts millions of rural households. The coffee berry borer has  benefited from rising temperatures in East Africa, increasing its range into areas that were previously too cool.

A 2011 study published in PLoS One, “The Influence and implications of Climate Change on Coffee Berry Borer and Coffee Production in East Africa,” utilized two types of climate modeling to measure current infestations in the region and investigate the extent to which H. hampei may continue to spread. Participating institutions include the University of Hanover, the International Center of Insect Physiology and Ecology in Nairobi, and the Agricultural Research Service in Maryland. The study was published in PLoS ONE, a peer-reviewed, open-access online publication.

Key findings in the study include:

• Coffee production levels are already under pressure due to weather events and related outbreaks of pests and diseases. “Between 2009 and 2011, C. arabica prices have increased by 160% mainly due to dramatically reduced production levels in East Africa and Latin America, particularly in Colombia.”
• Until 2001, the coffee berry borer was restricted to plantations at altitudes of 1,500 meters and below. Based on current climate-change trends, by 2050 its range will shift upward to 1,600-1,800 meters. “Areas currently considered as marginally suitable for the borer will become favourable for population persistence in the future.”
• The coffee berry borer currently reproduces at a rate of 1 to 4.5 generations per year at higher elevations. Based on climate change models, its reproduction rate could increase to between 5 and 16 generations per year. The East African regions most likely to be impacted include southwestern Ethiopia, the Ugandan side of Lake Victoria, and the Kenyan side of Mt. Elgon.
• Land suitable for coffee cultivation is already limited in East Africa, and the situation is likely to grow significantly worse with climate change. “It has been estimated that Colombian C. arabica plantations would have to be moved by 167m in altitude for every 1C of increase in temperature,” the authors state, something not feasible in Africa because of anticipated population growth and food security issues.
• The best strategy for slowing the coffee berry borer’s advances is planting shade trees, which can reduce ambient temperatures by as much as 4 degrees Celsius. Such a reduction “would imply a drop of 34% in the intrinsic rate of increase of the coffee berry borer,” the researchers state.

The researchers reference a number of related papers, including a two-year study of shaded and unshaded coffee plantations in Kenya: “H. hampei infestations levels in the shaded plantation were always lower than the sun-grown coffee, and remained below the 5% economic threshold level,” they note.

Tags: global warming, Africa

By Margaret Weigel | October 27, 2011