Environmental Geology
Soil Resources: The Coming Food Crisis?
Outline
A. In 1st World, the few feed the many. Grain is planted mechanically, requiring fuel, parts, labor. Fertilizer, herbicide, and pesticide are typically applied, requiring fuel, other resources, transport, and often clean-up! Irrigation requires energy to pump water. Harvest is mechanized (fuel, parts). Grain sold and transported to grain silo. Purchased by business to make food. Cost now includes transport, administrative and marketing structure, profit. Processed food sold to grocery store - more admin, marketing, labor, profit. Ultimately, purchased by consumer. In typical box of Captain Crunch ($4), how much of its value went to the farmer to buy the grain? A nickel! Doubling grain prices would thus add minimal cost to groceries because so little of any product's price comes from the actual cost of the underlying food material. Doubling grain prices would mean a lot to the farmer, who is probably the most underpaid person in our society.
Cattle raised in feedlots instead of grass pastureland require 7 kg of grain for each kilo of beef. Poultry = 2 kg input; Pork = 4 kg input. Meat is thus an inefficient way to convert grain to food for humans.
Figure 1. Farm labor versus energy used to produce US food, 1920-1970
B. In 3rd World, the many feed the many. Grain is planted by hand, possibly irrigated, harvested by hand, transported to nearby market, and sold. Labor-intensive and minimal energy investment.
Soil
Soil supports agriculture and all land-based ecosystems. Its a rather critical resource!
Soil: linked to geologic grocesses of physical and chemical weathering of rock surfaces. Effects of man and other organisms.
Present trends
Figure 3. Population, Food,
and Soil
Important concept: a finite amount of land is suitable for agriculture. Implications....
Statistic - total land being farmed has decreased about 10% since 1981 and has not changed significantly in the past 20 years. Ability to increase grain production thus requires increased yields per acre. Yields in key grains (wheat, rice, and corn) have leveled off in agriculturally advanced countries (Japan, China, US) and may not increase with present crop strains.
Soil erosion and its impact on grain production
Soil retention/erosion influenced by number of factors:
Ideally, average erosion rates should be less than or at worst, the same as the rate at which new top soil has formed.
In U.S., soil eroding 7-8 times faster than it is forming. In California, erosion typically 80 times faster than replacement.
The U.S. Soil Conservation Service estimates that about one-third of US topsoil that was present prior to widespread agriculture has been irretrievably lost through erosion.
Worldwide, soil erosion occurring at a rate of 20-100 times faster than replacement. An area the size of Virginia is abandoned every year due to soil erosion or contamination of soil from over-irrigation. Since 1957, China alone has lost an area of cropland equal to all the cropland in France, Germany, Denmark, and the Netherlands. Could have supported 450 million people, 40% of China's present population.
Discuss factors that contribute to loss of farmland:
In most areas where top soil has eroded, will take several hundred years or more for natural processes to replace soil that is lost every 25 years.
Soil Conservation
Practices for soil conservation and restoration: