Geography Reference
In-Depth Information
Fortunately, countries that contain rainforests have created national parks and preserves that will save
millions of acres for posterity. But millions of acres more stand to be lost unless preservation efforts
are greatly expanded.
Poor soils
Despite the lush forest cover, the tropical rainforest realm is underlain by infertile soils called
latosols. These are products of warm temperatures and high rainfall, which respectively en-
courage high microbial activity that breaks down topsoil nutrients, and wash them away (a
process called leaching ) by means of runoff or downward percolation of water through the
soil. Either way, the effect on soil nutrients is much like what happens to the contents of a tea
bag after it has been used a couple of times — it becomes weak.
If the soil is so bad, then why (you may ask) is the natural plant cover so lush? The answer is found
in root systems that tend to fan out laterally from the bases of plants rather than dig vertically into the
soil. This allows trees to effectively absorb nutrients in the topsoil before leaching does its thing.
Shifting cultivation
A large percentage of the people who live in rainforest countries farm for a living, many of who prac-
tice shifting cultivation, which has a particularly devastating effect on rainforests. In this form of ag-
riculture, farmers (and their extended families) clear an area of forest, grow crops on the plot for a
year or two, and then abandon it, only to move on (hence, shift) to a new area of forest and repeat the
process.
Soil infertility explains this practice. When farmers remove the trees, they also remove the sources
of leaf-fall that contribute to productive topsoil. With the nutrient source literally cut off and the soil
exposed to direct sunlight and rainfall, leaching is swift and sure.
When a plot of land has been abandoned, the forest reclaims it and the fertility of the soil gradually
improves. After lying fallow (plowed land that's not being farmed) for a number of years, it may be
used again. But population growth in most rainforest countries is so high that “recycled” land alone is
insufficient to meet local food needs. As a result, new areas of virgin rainforest must be annually cut
down and the acreage added to the inventory of land that is used for occasional shifting cultivation.
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