Digging Up The Truth on US Soil Erosion

CHURCHVILLE, Va.--For decades, some environmentalists have called modern farming unsustainable. One of their most serious charges is that aggressive planting generates dangerous levels of soil erosion.

Over and over they have predicted that topsoil losses portend a return to the Dust Bowl days of 1930s' America.

Now an industrious erosion expert from California has literally dug up the topsoil history of the Coon Creek watershed, centered in western Wisconsin, and found its steep, intensively farmed slopes are losing only 5 percent as much topsoil as they did in the Dust Bowl era.

Stanley Trimble, a professor of geography at the University of California at Los Angeles (and a part-time farmer in Tennessee), used historical records and 20 years of his own soil surveys to prove the critics wrong.

Trimble found that erosion in the Coon Creek watershed rose strongly after the prairie was plowed in the 1850s and skyrocketed during the droughts of the 1920s and 1930s.

However, erosion was sharply reduced by contour plowing, strip cropping and other techniques introduced by the U.S. Soil Conservation Service in the 1930s.

Coon Creek soil losses continue to decline, Trimble says, as farmers improve their methods of reducing runoff. Today's creek supports the brook trout once nearly eradicated by heavy sediment loads.

Trimble says Coon Creek farmers are not even making much use of the most powerful soil conservation systems: conservation tillage and no-till farming.

The Coon Creek watershed was chosen for intensive study in the 1930s. Trimble rummaged the Coon Creek soil data out of the National Archives and resurveyed the soil profiles in nearly 100 soil cross-sections across the basin's profile in the 1970s and again in the 1990s.

Trimble even dug down to find the old roads, railroads and building foundations that marked soil levels in 1900. At lower depths, he found the dark organic soils of the pre-1850 prairie.

Soil erosion has long been the biggest threat to the sustainability of the world's expanding population, and traditional low-yield farming systems have long suffered high erosion rates.

Modern farmers claim they are achieving both high yields and soil protection. But official Department of Agriculture estimates of soil erosion suggest modern farming has reduced soil erosion only slightly.

Lester Brown of the Worldwatch Institute, a Washington-based environmental group, has claimed huge worldwide soil erosion losses--26 billion tons a year--and specifically warned in 1980 that Corn Belt topsoil was rapidly disappearing.

Cornell entomologist David Pimentel published an article in the journal Science in 1995 in which he claimed the world had lost one-third of its arable land over the preceding 40 years. Pimentel based his conclusions mainly on his own estimate of 74 billion tons of annual soil erosion.

Asked about the soil erosion history in Coon Creek, Pimentel claimed that Trimble has studied sediments, not what actually happened in the fields. "Trimble has a good imagination."

However, Pimentel has little physical data to back up his own soil- loss estimates. In fact, there's been little systematic data gathered on soil erosion occurring outside the United States. Trimble's data from Coon Creek call into question even the official U.S. soil loss estimates.

Why do Brown and Pimentel invent huge soil losses? Maybe because both have built global reputations by declaiming against overpopulation.

Brown has been predicting massive world famines for the last 25 years and claims that recent gains in world food production are only "an illusion of progress."

Pimentel asked in a 1994 study, "Does human society want 10 to 15 billion humans living in poverty and malnourishment or one to two billion living with abundant resources and a quality environment?"

Modern high-yield agriculture is one of the cornerstones of today's high-tech prosperity. By suggesting that it poses a lurking threat to topsoil, Brown and Pimentel are striking at the core of modern food security--and our children's prospects for living in abundance.

The Agriculture Department has a built-in conflict of interest. If soil erosion is not a big problem, then there is no reason for the country to pay a billion dollars annually to have a soil conservationist in every one of America's 3,000 counties handing out subsidies to soil-conserving farmers.

A few years ago, I met with a group of urbanites in Indiana, at one of those weekend rallies for well-meaning political types. I was amazed to find that they sincerely believed the deep, level soils surrounding them were silently disappearing beneath our feet.

They were not impressed with the conservation tillage practiced on their neighbors' farms. They got upset when I suggested that if they really wanted to combat soil erosion, they should send their local soil conservation agent to a backward farming region like Indonesia, where erosion is actually taking place.

Asked about high soil erosion estimates that imply the need for global depopulation, Trimble says, "They owe us physical evidence." He's got a point.

OPINION ARTICLES and letters to the editor are welcome. Send submissions to Sally Heinemann, editorial director, Bridge News, 3 World Financial Center, 200 Vesey St., 28th Floor, New York, N.Y. 10281-1009. You may also call (212) 372-7510, fax (212) 372-2707 or send e-mail to opinion@bridge.com.