For Eva: Scientists Decode Dust Bowl

Sunday, May 11, 2008
Scientists Decode Dust Bowl
By John Fleck
Albuquerque Journal Staff Writer

The dust storm that rolled across Clayton on May 29, 1937, looked like it wanted to swallow the world. For farmers across mid-America, in some sense, the dust storm and a host like it really did swallow their world. Drought during the 1930s turned their fields to dust, wind blew the dust away and farming on America's Great Plains was never the same. They call it the Dust Bowl.

It has been known since the 1930s that farming practices helped cause the dusty part the Dust Bowl, removing natural vegetation that held the dirt in place. Precious topsoil simply blew away, degrading farmland. Major changes in farming practices adopted in response continue to this day.

But new research suggests that the effect of agriculture may have been worse than anyone realized at the time. All that dust actually decreased rainfall, according to a team of scientists from Columbia University and NASA's Goddard Institute for Space Studies, both in New York.

A drought that might otherwise have been limited to Mexico, New Mexico and Texas instead spread across much of the Great Plains, according to the scientists.

The extent of the drought has always been a puzzle to climate scientists, according to Ben Cook, a researcher at both Columbia and Goddard who was lead author on a new paper reporting the findings.

Scientists say they have a handle on the way changing ocean temperatures influence drought across North America. The slow warming and cooling of the Pacific and the Atlantic over periods of years to decades influences rainfall patterns.

When the oceans are in the right alignment, droughts result.

Richard Seager, a professor at Columbia and one of Cook's co-authors, fed ocean temperature data into computer simulations to re-create many of the major North American droughts of the last two centuries.

But the Dust Bowl drought has always been a puzzle, Seager and Cook said in interviews.

Ocean temperatures at the time were consistent with a drought centered over Mexico, eastern New Mexico and Texas?- a "classic Southwestern drought," Cook called it. But the Dust Bowl drought stretched far to the north and east, to the Dakotas and across much of the Great Plains.

Looking for an explanation, Cook and his colleagues found data on dust and added the information to their computer simulation. The resulting drought patterns the computer spit out looked much more like what actually happened during the 1930s.

Cook said all the extra dust reflected sunlight. This cooled the air, reducing evaporation from the ground and thus decreasing the amount of moisture available for rainfall.

Farming practices today are much different than in the 1930s, said David Graham, county extension agent in Union County.

The county, in New Mexico's northeast corner, was the area of the state hit hardest by the Dust Bowl.

Back then, every acre of ground was plowed, Graham explained. When the soil wore out, a farmer would move to the next available acre, leaving the ground bare and unprotected. The economic incentive, Seager said, was to plow every bit of ground.

Today, Graham said, grass is planted on land that is not in use for farming, and "conservation reserves" of unfarmed land are set aside to help soil conservation. Cook and his colleagues say those practices, instituted immediately after the Dust Bowl, can prevent a worst-case repeat of the Dust Bowl conditions here.

But they say their findings might apply to other parts of the world, including China and sub-Saharan Africa, where the same practices that triggered the Dust Bowl here are still in use today.