Land Degradation

I AND DEGRADATION_mostly due to soil erosion, mineral depletion, and urbanization_is becoming a major problem worldwide. Currently, the full scope of the problem is hidden because lost vitality is compensated for by intensified use and increased application of artificial fertilizers. In the end, these strategies only exacerbate the problem, leading to a total collapse of soil viability.

Since 1945, the total land degraded by soil depletion, desertification, and the destruction of tropical rainforests comes to more than 5 billion hectares, or greater than 43 percent of the Earth's vegetated surface.1

Each year, 10 million hectares of productive, arable land are abandoned due to severe degradation.2 At the same time, 5 million hectares must be added to production to feed the extra 84 million humans born each year. In all, 15 million hectares are needed yearly to make up for losses and increased population. Most of this land is coming from the forests,3 accounting for 60 percent of world deforestation.4

It takes 500 years for nature to replace 1 inch of topsoil.5 Approximately 3,000 years are needed for natural reformation of topsoil to the depth needed for satisfactory crop production.6 In a natural environment, topsoil is built up by decaying plant matter and weathering rock, and it is protected from erosion by growing plants. In soil made vulnerable by agriculture, erosion is reducing productivity up to 65 percent each year.7 Former prairie lands, which constitute the breadbasket of the United States, have lost one half of their topsoil after being farmed for about 100 years. This soil is eroding 30 times faster than the natural formation rate.8 Food crops are much hungrier than the natural grasses which once covered the Great Plains. As a result, the remaining topsoil is increasingly depleted of nutrients. Soil erosion and mineral depletion remove about $20 billion worth of plant nutrients from US agricultural soils every year.9 Much of the soil in the Great Plains is now little more than a sponge into which we must pour hydrocarbon-based fertilizers in order to produce crops.

Erosion rates are increasing throughout the world. China is losing topsoil at the rate of *0 tons per hectare per year (t/ha/yr).10 During the spring planting season, Chinese soil can be detected in the atmosphere as far away as Hawaii." China's need for food exceeded the capacity of its agricultural system decades ago. The Chinese have pushed their agricultural lands to the very limit, using artificial fertilizers and pesticides to force every bit of production from the land. And still they must import prodigious quantities of grain from the US and other countries in order to feed their population.12

Agricultural production in some parts of Africa has declined by 50 percent due to soil erosion and desertification.13 As with China, soil eroded from Africa can be detected in Florida and Brazil.1* Serious production losses (in the 20 percent range) have also been reported for India, Pakistan, Nepal, Iran, Jordan, Lebanon, and Israel.15 Globally, the loss of 75 billion tons of soil per year costs the world about $400 billion annually, or about $70 per person per year.16

In the US, assuming erosion by wind and water at a rate of 17 t/ha/yr, the onsite costs of irrigation to replace lost soil moisture and fertilizers to replace lost nutrients translates into approximately $28 billion per year, in 1992 dollars.17 In addition to this, there are the offsite costs of soil erosion: roadway, sewer, and basement siltation; drainage disruption; foundation and pavement undermining; gullying of roads; earth dam failures; eutrophica-

tion of waterways; siltation of harbors and channels; loss of reservoir storage; loss of wildlife habitat and disruption of stream ecology; flooding; damage to public health; and increased water treatment costs. Offsite costs are estimated at $17 billion per year, also in 1992 dollars.1' The combined cost is $45 billion per year, or about $ioo/hectare of pasture and farmland, which increases the production costs of US agriculture by 25 percent.19

Approximately three-quarters of the land in the United States is devoted to agriculture and commercial forestry.20 Of this, every year more than two million acres of cropland are lost to erosion, salinization, and water logging. On top of this, farmland loses another million acres to urbanization, road building, and industry annually.21 Between 1945 and 197', an area equivalent to the states of Ohio and Pennsylvania was blacktopped. Of the land taken for housing and highways, almost half was among the most agriculturally productive land in the country.22 Incidentally, only a small portion of US land area remains available for the solar energy technologies necessary to support a solar energy-based economy. The land area for harvesting biomass is likewise limited. For this reason, the development of solar energy or biomass must be at the expense of agriculture.

This is the cost of poor farm management. Soil degradation is caused primarily by loss of vegetation cover. It can be combated by a number of techniques, including no-till agriculture, contouring, cover cropping, crop rotation, contour strip cropping, contour buffer planting, terracing, grassed waterways, farm ponds, check dams, and reforestation. Instead, we presently make up for the loss in soil fertility with artificial fertilizers derived from natural gas. It is to be wondered why we bother planting crops in the ground at all — as opposed to growing them with hydroponics — except that the ground provides a cheap and abundant medium.

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