|Impact of Agriculture in the Rainforest|
Agricultural use of some rainforest land proves to be a failure because of the nutrient-deficient, acidic soils of these forests. Nevertheless, many commercial agricultural projects are still carried out on rainforest lands, although many of these revert to cattle pasture after soils are depleted. Some floodplain regions, like those of the lower Amazon (várzea), are more suitable for commercial agriculture because annual floods replenish nutrient stores.
Generally forest clearers use slash-and-burn techniques to clear land, but on a much larger scale than traditional practices. Instead of burning a mere 2-10 acres (1-4 ha), agriculturalists burn hundreds to thousands of hectares. This slash-and-burn technique is generally wasteful since it is only occasionally that trees with timber value are removed before the forest is clear cut and left to dry. Following cutting, the area is burned to release nutrients locked up in vegetation and produce a layer of nutrient-rich material above the poor soils of the former tropical forest. The cleared area is quickly planted and supports vigorous growth for a few years, after which the nutrient stock is depleted and copious amounts of fertilizer are required to keep the operation viable. Fertilizer may be washed into local streams, affecting fish and aquatic life. When the use of fertilizer is deemed no longer efficient, the land is abandoned and allowed to revert to scrub. Drought-resistant grasses may move in or cattle ranchers may plant imported African grasses for cattle grazing. The land is now only marginally productive and a limited number of cattle can subsist in the area.
When the land is suitable for agriculture, generally large single cash crops like rice, citrus fruits, palms, coffee, coca, opium, tea, soybeans, cacao, rubber, and bananas are cultivated. Some of these crops are better adapted to such conditions and last longer on cleared forest lands. However, there are several problems with this type of monoculture (single crop plantations) in the tropics, besides the loss of forest. First, such planting of a single crop makes the crop highly vulnerable to disease and pests, as periodic infestations have shown in Brazil, India, and other places. In natural rainforest, widespread infestations are rare because individuals of a given species are widely dispersed. Second, the planting of monocultures can be economically risky with the price fluctuations so common in international commodities markets. Additionally, a single cold spell or drought can devastate a tremendous part of the agricultural economy.
Soybeans have become one of the Brazil's most important crops in the Amazon, as well as in the nearby cerrado grassland ecosystem. Today soybeans are flourishing—since 1998, Brazil has added 30 million acres of soybeans, and American firms are aggressively expanding their presence in the Brazilian agricultural sector. Brazil will likely soon supplant the United States as the world's leading exporter of soybeans, at the expense of the forests of the Amazon basin.
More on soybeans in the Amazon
Paving of road brings change in the Amazon rainforest
Chinese demand drives road-building and deforestation in the Amazon
Brazil's grasslands could replace food production of American heartland
Sustainable Agriculture in the Rainforest
[full photo version]
Continued: Cattle Pasture
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