Eastern Africa caught in vicious weather cycle

Researchers warn that eastern Africa may soon experience another catastrophic dry period, possibly lasting decades.

February 14, 2000
Web posted at: 12:24 PM EST (1724 GMT)

By Environmental News Network staff

Separate from global warming, natural climate change in eastern Africa over the past millennium has resulted in extended periods of drought followed by periods of heavy rainfall, a new study shows.

"We have shown that there have been large fluctuations in water availability on a decadal to centennial time scale and that these changes occurred due to natural oscillations in climate," said Brian Cumming, a biologist with the Paleoecological Environmental Assessment and Research Laboratory at Queen's University in Canada and co-author the study.

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"Changes in precipitation were related to changes in solar intensity," he explained. "During times of lower solar activity over the last thousand years, rainfall was high in eastern Africa whereas in times of increased solar activity rainfall was low."

Cumming collaborated on the study with Queen's University biologist Kathleen Laird and University of Ghent biologist Dirk Verschuren. Their report was published in the Jan. 27 edition of Nature.

The researchers warn that a catastrophic dry period, possibly lasting decades, might visit eastern Africa again in the next 50 to 100 years. A drought of this magnitude could trigger large-scale migration, political upheaval and economic and social devastation.

In the past several centuries, eastern Africa, the focus of a study on weather patterns, has endured three droughts followed by periods of relatively abundant water supply.

"Long droughts have been implicated in the collapse of many ancient civilizations on virtually every continent, including our example in eastern Africa, the Mayan in Central America and many others," said Cumming.

While the study indicates that drought occurs as part of the natural climate system, the researchers note that global warming must also be considered in any forecast of future conditions. "Our concern is that human industrialization could be a trigger for extreme climate changes on a global scale in the future," said Cumming.

Over the past 800 years, eastern Africa has endured three droughts followed by periods of relatively abundant water supply. Development and population growth increased during the abundance. "So, if an extreme climate change does occur in the future it could create widespread devastation," said Cumming.

Cumming and colleagues conducted their research on Lake Naivasha in Kenya. "By examining the physical and biological remains in sediment cores from lakes you can reconstruct past environmental conditions over the last several millennia," he said. "We examined the physical and biological remains of organisms that are sensitive to changes in water level and salinity. What we found was that when water levels were high civilizations thrived, and when they were low civilizations collapsed."

"From a human point of view, the more we know, the better off we'll be," Cumming added. "In a region that is susceptible to droughts, wise water use and land management are a necessity."

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Queen's University, Kingston, Canada
National Drought Mitigation Center
NOAA's Drought Information Center

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