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Droughts of Past Yield Lessons for a Warming World

Droughts of Past Yield Lessons for a Warming World

Already an expert on how global warming and drought affect ecosystems, Geography Professor Glen MacDonald is now delving more deeply into how these forces will affect people, and what local and regional leaders can do.

Kevin Matthews Email KevinMatthews

In the 12th century this region suffered sustained low flows in the Colorado and Sacramento Rivers and low rainfall, elements of what MacDonald calls a "perfect drought," for a period of 40 to 60 years.

UCLA Today

Glen MacDonald, the new director of the UCLA Institute of the Environment (IoE), has spent much of the last year conducting research in the subtropical areas of the Northern Hemisphere that are particularly prone to drought, both recently and in the distant past.

The Syrian stretch of the Euphrates, the Indus River Valley region where Pakistan and India meet, and other stops along the way were far from home for a boy from East San Jose, Calif., the first person in his immediate family to graduate from college.

Already an expert on how global warming and drought affect ecosystems, MacDonald is now delving more deeply into how these forces will affect people, and what local and regional leaders can do. On his travels, funded by a Guggenheim Fellowship, he was struck by how nearly the world map of drought overlaps the world map of troubled borderlands and potential political instability. The Middle East, Pakistan-India, Egypt-Sudan and Mexico face water resource challenges.

"You step back and you say, 'This is not good.' The last thing any of those places needs is an added perturbation which starts driving people from the land and causes societal unrest in areas which are already volatile."

As a UC Berkeley undergraduate, MacDonald pictured himself working on forestry and natural resource conservation at a government agency. He ended up as a university professor — a natural scientist with more than 120 peer-reviewed papers about ancient river flows, disappearing Arctic lakes and more — because he loved teaching and wanted the total freedom of inquiry. "Your only restriction is your imagination and your work ethic," he said.

Accordingly, the range of drought-related questions he's addressing for a planned book and potential documentary film is really vast. Did civilizations in North Africa, Mesopotamia and the Indus River Valley decline more than 4,000 years ago, in spite of advanced water management tools, because of long droughts brought on by natural climate change? How prepared are these regions today for a prolonged decrease in natural water resources? And what will happen to world food prices and California's food security, not to mention its carbon footprint, if dryness that is predicted by global-warming models forces land out of agricultural use? Just as crucial for this region, how long can droughts last?

On the matter of long-term drought, MacDonald has a track record and stark advice for Southern Californians: "If the climate behaves the way it did the last time we had global warming, we should probably get ready to settle in to a more arid climate," he advised. In the 2005 annual Environmental Report Card put out by the IoE, the geography professor warned that local officials were underestimating the likely duration of new droughts, which in the past century have not lasted more than about five years.

However, tree ring evidence assembled by MacDonald as well as other UCLA teams shows that local dry spells can go on for more than a decade. In the 12th century this region suffered sustained low flows in the Colorado and Sacramento Rivers and low rainfall, elements of what MacDonald calls a "perfect drought," for a period of 40 to 60 years. (That coincided with a simultaneous drop in volcanic activity and a spike in solar radiance that produced an episode of natural climate warming.)

For the century to come, which is expected to be hotter than the 12th century because of human activity, fast-growing California needs to find solutions that can be implemented, said MacDonald. He assumed the IoE directorship this month convinced that just this sort of multidisciplinary organization, in which lawyers and social scientists share ideas with engineers and natural scientists, has a special role to play in California and the contemporary world.

"As a scientist, I could provide lots of solutions for greenhouse warming and for water issues. The fact is we can't either afford them economically or society won't accept them, we need economically and sociologically realistic solutions" he said.

Given the IoE's location in the media capital of Los Angeles, MacDonald also wants the institute to get the word out about environmental issues "in a non-biased, honest way that people can digest and then act upon."

His own studies of the history of water scarcity and drought mitigation fit in, he said, because the past can tell us a lot about what kinds of general strategies allow societies to survive over time. There's a lesson to be learned from previous civilizations who successfully managed resources for many centuries and from those who did not.

"One of our greatest dangers is probably being too smug [and] assuming that, 'Well, technologically we can manage our way through this. We have nothing to learn from the past.'"

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