SUBSISTENCE AGRICULTURE AND DEFORESTATION
A third to two-fifths of tropical deforestation is caused by subsistence activities on a local level by people who simply use the rainforest's resources for their survival. Having neither the money nor the political power to acquire holdings on productive lands, these transient settlers follow and settle along roads constructed in the rainforest by development or extractive firms. After cutting trees for building material, these people use the slash-and-burn technique to clear the surrounding forest for short-term agriculture. First, understory shrubbery is cleared and then forest trees not used as construction material. The area is left to dry for a few months and is then burned. The land is planted with crops like bananas, palms, manioc, maize, or rice. After a year or two, the productivity of the soil declines, and the transient farmers press a little deeper and clear additional forest for more short-term agricultural land. The old, now infertile fields are left for waste or sometimes used for small-scale cattle grazing.
Rondônia, Brazil. Top: June 1985, Bottom: August 1992
These photographs show deforestation in the Brazilian state of Rondônia. The solid dark green areas show the remaining tropical rainforest canopy. Two urban areas separated by a small river can be seen near the center of the photograph. Photos courtesy of the Image Science and Analysis Laboratory, NASA-Johnson Space Center.
Although this sort of slash-and-burn agriculture has been used for centuries by indigenous peoples, the practice has been carried out in a careful, small-scale, rotational manner, which ensures relative sustainability. In the past the clearing was left idle for 20 to 100 years, so the forest could recover and again provide fertile land and useful timber. The situation is different today. So many people are practicing slash-and-burn agriculture in a non-rotational manner that fields do not have time to return to secondary forest as they do after natural disturbances. The clearing cycles are becoming shorter and shorter, and in some cases it is only 5-8 years before the forest scrub is again cleared. Eventually, the rainforest ecosystem fails and is replaced by tough grasses which can tolerate the short cycles.
The colonizer not only brings his fire to the rainforest, but also his domestic animals and diseases. Domestic animals decimate local wildlife by infecting them with disease and eating their young, while local indigenous peoples, where they exist (mostly limited to remote parts of the Amazon today), can be infected by the colonists' diseases. When not actively burning forest for agricultural clearing, the colonizer cuts fuel wood and hunts wildlife for food.
It is not solely the fault of the landless peasants for their plight; the unequal distribution of land and inability of the government to provide sufficient legal mechanisms for them to gain title to land are also to blame. These people have few options, and without a better alternative they will continue to do what they must to survive: destroy the forest. This subsistence activity on a local level is the greatest threat to the future of the rainforest and the most difficult to address, especially in regions with fast-growing populations.
Historically the colonization of rainforest land was encouraged by tropical governments that funded programs to move urban poor out of cities to the "unclaimed" forest areas. The programs were facilitated by laws that allowed the free ownership of forest lands simply by clearing and occupying them. In the 1970s, 1980s, and 1990s these programs often contributed to conflict between colonists and traditional forest dwellers. Further incentives came from the development of roads that opened up once remote forests to settlement.
Brazil and Indonesia had the largest state-backed colonization schemes. Indonesia's was known as the transmigration program
, which aimed to alleviate some of the population pressures of the central islands, acquire resources, and establish regional hegemony over local populations that may harbor ambitions for political autonomy. Transmigration continues today but is much diminished from its peak in the 1970s and 1980s.
Aerial view of rainforest cleared for agriculture in Suriname. Click image for more information. (Photo by R. Butler)
- What is slash-and-burn agriculture?
- Why do colonists and poor farmers destroy the rainforest?
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