Drought points to a need for better planning in arid regions

John Wesley Powell said it all. He and other 19th-century explorers called large parts of "the Sunbelt" and "America's wheat lands" the "Great American Desert" and considered them unfit for agriculture or settlement.

These explorers would not be surprised by the heat and drought now devastating much of this land and adjacent areas. Modern climatological research confirms the 19th- century assessment of the harshness of these lands, which technologies such as air conditioning and mining of underground water reserves have moderated but not overcome.

Looking for clues to past climate in tree rings, pollen deposits, and other such "proxy" data, as meteorologists call them, scientists have found tantalizing hints of cyclical weather patterns. There is little agreement among experts as to the reality of these cycles and little faith in their predictive value. But one fact stands out North America's semiarid lands are subject to recurring drought. As Jack Runkles, director of the Texas Water Resources Institute at Texas A & M University, notes "drought . . . is a normal part of our environment, and we've got to take this into account in our planning."

Climatologists have been saying this for many years. However, state and federal planners, developers and farmers have paid no more attention to these modern experts than they did to Powell and his associates a century and more ago. Memories of weather are short term. And because climatologists cannot agree on past weather patterns or forecast next year's rainfall, people may tend to discount their warnings.

But climatologists note that the uncertainties of their science are no reason to ignore the extremes to which our weather can run or to forget that such extremes can recur at any time.

Helmut Landsberg of the University of Maryland, who has devoted many decades to studying climate, has expressed it this way: "In the face of uncertainty and unknown causes, the best estimate for a few years or even a decade or two is the assumption that climatic fluctuations will take place as in the past."

Of all the periodicities experts have found in climatic data, a roughly 20- to 22-year drought cycle in the North American high plains is the one for which the evidence is strongest.

J. Murray Mitchell Jr., senior climatologist at the Environmental Data Service of the US National Oceanic and Atmospheric Administration, hesitates to say that you can forecast future drought on the basis of that cycle. Instead, he sees it as another warning to be prepared for drought in America's marginal lands.

According to the cycle, the next high-risk period for major drought would be the mid-1990s. Perhaps, Dr. Mitchell suggests, the wisest thing to do is to assume that such drought might indeed occur and be prepared for it. On the other hand, he has warned, "A whopping drought can occur at the wrong part of the sunspot cycle." And that is what has happened now.

Thus more than a century of climatological study has only reinforced Powell's assessment. Yet Americans have consistently acted as though drought were only an occasional nuisance that could be endured or ameliorated as they got on with the challenge of developing their marginal lands.

Henry Landsford, a writer on weather who joined with atmospheric scientist Walter Orr Roberts in studying the history of this problem, has observed: "During the 1880s, the erratic rainfall on the plains was a little less scanty than it had been in previous years. This produced a number of theories as to why the climate supposedly was growing more favorable for the farmer. Railroad promoters and land speculators said the 'rain belt' was moving westward. 'Rain follows the plow' was the slogan. . . ."

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