Megadroughts: What Causes, and What Solutions?

By Chris Mooney | June 16, 2010 10:20 am

This is a guest post from a member of Science in the News (SITN), an organization of PhD students at Harvard University whose mission is to bring the newest and most relevant science to a general audience. For over a decade, SITN has been presenting a fall lecture series at Harvard Medical School, with talks on a diversity of current and newsworthy topics, such as stem cell biology and climate change. SITN also publishes the Flash, an online newsletter written by graduate students at Harvard, which presents current scientific discoveries and emerging fields in an accessible and entertaining manner. SITN engages in additional outreach activities such as “Science by the Pint”, and hopes students at other institutions will also make the commitment to strengthen science communication.

The following post is from Harvard graduate student Atreyee Bhattacharya.

As devastating drought threatens sub-Saharan Africa, and millions are faced with starvation and socio-political conflict, a question might loom large on the minds of policy makers: “How do we prepare for a potentially several decade-spanning drought, in a region where survival of our population depends mainly on rain-fed agriculture?”

Research has shown that dry spells spanning several decades, also known as megadroughts, have been regular feature of sub-Saharan life for thousands of years. Most recently, droughts in the late 18th century and 1870s, both much longer and more severe than the American 1930s Dust Bowl and the West African Sahel drought of 1968-73, caused millions to perish. And these severe droughts occurred before pervasive European colonization, at a time when the native population still maintained a nomadic lifestyle that allowed them to move their herds in search of greener pastures.  With agricultural stability came a new hazard- dependence of food production on rainwater, in a region where its availability is linked to a fragile climate balance;  and a balance that increasingly tips to the wrong side.

Climate records suggest that, in terms of duration of dry conditions, nature is being kinder to sub-Sahara now than it has been in the previous centuries [1,2]. However, some climate modeling studies indicate that the effects of rising sea surface temperatures on the inherent variability of rainfall in sub-Saharan Africa might cause the current droughts to get worse [3]. And these climate predictions [3,4] don’t predict the cumulative effects of worsening drought plus the growing population, fragile economic conditions, tribal wars and spread of diseases. These factors already work to undermine the ability of sub-Saharan society to sustain an agriculture-based economy in region where failure of rainfall is more the norm than anomaly.

It seems that nature has dealt an unfair hand to Sub-Saharan Africa. However, as a global community, can we prevent the suffering from a climate change-fueled calamity? Researchers say there is hope. Most of it is tied to careful water resource management techniques. Planting drought resistant crops and reducing dependence on irrigation might be essential for the region’s survival. Debate rages however on whether some of those resistant crops should be Genetically Modified (GM). In the meantime, scientists are searching for and developing better crops, including breeding plants with better roots and screening for plants that produce less toxins in stressful conditions. Survival, and success, in the face of a sub-Saharan megadrought may require a science-fueled “Second Green Revolution.”


1. Shanahan et al. (2009) Atlantic Forcing of Persistent Drought in West Africa. Science. Vol. 324. pg. 377 – 380

2. Nicholson, S. E. and Palao, I. M. (1993) A re-evaluation of rainfall variability in the Sahel: Characteristics of rainfall fluctuations. International Journal of Climatology. Vol.13, pg. 371-389

3. Giannini et al. (2003) Oceanic Forcing of Sahel Rainfall on Interannual to Interdecadal Time Scales. Science Vol. 302, pg. 1027

4. Held, I.M. et al (2005). Simulation of Sahel drought in the 20th and 21st centuries. PNAS Vol. 102, pg. 17891-17896

Current links of interest:

British researchers screening for crops that produce less toxins when stressed:

Reuters article: “African agriculture suffers from erratic climate”

Christian Science Monitor article “How Science Could Spark a Second Green Revolution”; highlighting work by a scientist using non-GM methods (

The idea that we could fertilize and irrigate our way out of this problem was the first Green Revolution” led by Nobel Peace Prize-winner Norman Borlaug and others, Lynch says. The second Green Revolution is going to be how we get plants to grow productively with less water and artificial fertilizer, he says.

That’s where Lynch’s idea for improving roots comes in. He calls the concept “steep, cheap, and deep” – developing crop roots that grow steeper and deeper into the soil, making them able to find more moisture and nutrients, thereby reducing need for irrigation and nitrogen fertilizers.

Business Week article “The Seed Makers Who Don’t Pray For Rain”; business of drought-resistant GM plants (

Besides its work on drought-tolerant corn, Monsanto is engineering cotton, wheat, and sugar cane seeds for drier climes. Developing crops that require less irrigation not only contributes to more sustainable farming, Grant says, but also will help farmers in the developing world. Monsanto and BASF are donating drought-resistant corn seeds to farmers in sub-Saharan Africa through the Nairobi-based African Agricultural Technology Foundation.


Comments (5)

  1. Guy

    Wasn’t there a study done that showed pollution particles affect weather patterns? Africa depends heavily on rainfall for agriculture. When you mess around with where the rain falls and how much, it is going to have an adverse effect on traditional growing areas. I see two main possibilities; change or adapt. We have to either change our ways so there is less pollution or adapt to a tough new world of our own making.

  2. Nullius in Verba

    You might be interested in this link as well. It’s a bit old, but it just shows how it comes and goes.

    And there were monsoons in the Sahara up to about 3500 BC, apparently due to it getting more sun in the summer back then.

  3. Guy,

    you are right. It is surely a possibility that dust emitted from the Sahara-Sahel region can affect weather patterns, especially monsoon. The idea was very popular in the 1970’s. You may want to look into something called ‘ Charney’s hypothesis’. However new research ( both climate modelling and paleoclimate studies) shows that it is the interplay of sea surface temperature (mostly in the Atlantic and Indian ocean) which drive these drought cycles over the last 1000 years or so.


    The realtion of African monsoon to increased summer insolation operates on time scales larger than these drought cycles and when the summer insolation is stronger, there was more rainfall, which led to the greening of Sahara some 8000 BP. But since 5000 BP the insolation decreased, due to motion of earth’s tilt about its axis which has led to the gradual drying up of the Sahar into a desert that we see now. But the drought cycles in sub saharan africa is not an artefact of the summer insolation.

  4. Nullius in Verba


    Yes, I know. There is climate change on every time scale.

  5. Jackson

    Thanks Chris for an interesting post.


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About Chris Mooney

Chris is a science and political journalist and commentator and the author of three books, including the New York Times bestselling The Republican War on Science--dubbed "a landmark in contemporary political reporting" by and a "well-researched, closely argued and amply referenced indictment of the right wing's assault on science and scientists" by Scientific American--Storm World, and Unscientific America: How Scientific Illiteracy Threatens Our Future, co-authored by Sheril Kirshenbaum. They also write "The Intersection" blog together for Discover blogs. For a longer bio and contact information, see here.


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