Hope's Edge_ The Next Diet for a Small Planet - Frances Moore Lappe [50]
MINING THE SOIL
The loss of billions of tons of topsoil threatens our food security only if we are losing topsoil faster than nature is building it. The difficulty is knowing how fast nature works. The most widely accepted rule of thumb is that we can lose up to five tons of topsoil per acre per year without outpacing nature’s rebuilding rate—yet one-third of the nation’s cropland already exceeds this limit, the Department of Agriculture estimates, and one out of eight acres exceeds the limit almost three times over.43 This is bad enough, but many soil scientists challenge the standard itself, suggesting it applies only to the top layer of the soil. Soil formation from the underlying bedrock may proceed ten times more slowly.44 If these scientists are correct, we are mining the soil on most of our cropland.
LOST SOIL, LOWER YIELDS
In some areas we are already experiencing lower yields due to erosion and the reduction in fertility it causes. The Department of Agriculture estimates the annual dollar value of the loss just from water erosion at $540 million to $810 million.45 Adding wind erosion may increase that estimate by 30 percent.
“In our area of Nebraska you see hilltops eroded—completely naked,” says Marty Strange of the Center for Rural Affairs. “Yet farmers are still getting 90 to 95 bushels of corn an acre. Farmers don’t believe they are losing productivity.” They use chemicals to make up for the soil’s lost natural fertility, but the cost of fertilizer has risen 200 percent since 1967 and is likely to keep rising. Higher production costs must ultimately mean higher food prices.
We also pay in our taxes, for billions of dollars have gone toward conservation measures (although this spending is shrinking, while the need increases). Moreover, the soil washed from farmlands ends up in rivers, streams, and reservoirs. Dredging sediment from rivers and harbors, the reduction in the useful life of reservoirs, and water purification—these costs amount to $500 million to $1 billion a year.46
Thus, the direct and indirect costs of soil erosion already approach $2 billion a year.
BUt WHY?
Why is soil erosion accelerating, despite 34 Department of Agriculture programs related to soil and water conservation? There are several reasons:
• the increased tillage of soil so fragile it probably should have remained uncultivated. The government estimates that 43 percent of the land used for row crops in the Corn Belt is composed of highly erodible soils.47
• the increased planting of row crops, especially the feed crops corn and soybeans, which make the land particularly susceptible to erosion.
• the growing neglect of conservation practices, including the removal of shelterbelts planted during the Dust Bowl era to protect the soil. By 1975 the total real value of soil conservation improvements had deteriorated over 20 percent from its peak in 1955.48
These are the reasons, but what are the causes? Unfortunately, they lie in the economic givens that most Americans take as normal and proper. Squeezed between ever higher costs of production and falling prices, farmers must increase their production. They plant more acres, including marginal land susceptible to erosion, and they plant what brings the highest return, even if this means continuous planting of the most erosion-inducing crops, corn and soybeans. “The most erosive production system—continuous corn—produces the highest net income,” according to researchers at the University of Minnesota.49
Fertilizers: Becoming Import-Dependent
To determine a price for grain which reflects all its costs would also mean looking at the fertilizers required to mask our lost fertility and continually increase production. Higher yields and continuous cropping deplete soil nutrients, so that ever greater quantities of fertilizer must be used. This vicious circle caused our nation’s use of chemical fertilizer