Aerial view of rainforest cleared for agriculture. (Photo by R. Butler)
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SUBSISTENCE ACTIVITIES
Almost half 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.
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Rondônia, Brazil. Top: June 1985, Bottom: August 1992
These photographs, showing the destruction of tropical rain forests, provide a visual indication of the rate of deforestation that is taking place in the state of Rondônia, which has been especially hard hit by deforestation. The amount of clear-cut area now exceeds the area of remaining rainforest timber stands. 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 and text are courtesy of the Image Science and Analysis Laboratory, NASA-Johnson Space Center.
The International Fund for Agricultural Development estimates that 10 million hectares of tropical forest are temporarily cleared every year for shifting agriculture. For comparison, FAO says that about 10.4 million hectares of tropical forest were permanently deforested each year between 2000 and 2005.
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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, 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.
In some countries -- though less so today than during the 1970s and 1980s -- the colonization of rainforest land is encouraged by developing governments who would rather have people living on their own land, creating GDP, than in the slums of the crowded cities, consuming GDP. Many governments lack the resources and foresight necessary for proper urban planning and employment. Thus laws are passed by legislatures that promote the clearing of primary forest by allowing free ownership of such lands. In Peru and other countries, for unoccupied or unused land that has been settled or cultivated for a specified amount of time, the land rights revert to the settler regardless of the previous owner (in some cases even if it was a reserve or national park).
The governments of other countries like Brazil and Ecuador encourage settlement of the Amazon Basin by opening roads and offering tax incentives to settlers. Indonesia has a huge resettlement program in the outer islands of the country (Papua, Sulawesi, Kalimantan, Sumatra) to alleviate some of the population pressures of the central islands, develop new regions for economic growth, and to establish regional hegemony over local populations that may harbor ambitions for political autonomy.
Review questions:
- What is slash-and-burn agriculture?
- Why do colonists and poor farmers destroy the rainforest?
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Continued: Economic Restructuring
This article was written by Rhett A. Butler [bibliographic citation for this page] and was last updated on the most recent date listed in the column on the right side.
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Recent news
Humans drove rainforest into savannah in ancient Africa
(02/09/2012) Three thousand years ago (around 1000 BCE) several large sections of the Congo rainforest in central Africa suddenly vanished and became savannah. Scientists have long believed the loss of the forest was due to changes in the climate, however a new study in Science implicates an additional culprit: humans. The study argues that a migration of farmers into the region led to rapid land-use changes from agriculture and iron smelting, eventually causing the collapse of rainforest in places and a rise of grasslands. The study has implications for today as scientists warn that the potent combination of deforestation and climate change could flip parts of the Amazon rainforest as well into savannah.
New book series hopes to inspire research in world's 'hottest biodiversity hotspot'
(01/17/2012) Entomologist Dmitry Telnov hopes his new pet project will inspire and disseminate research about one of the world's last unexplored biogeographical regions: Wallacea and New Guinea. Incredibly rich in biodiversity and still full of unknown species, the region, also known as the Indo-Australian transition, spans many of the tropical islands of the Pacific, including Indonesia's Sulawesi, Komodo and Flores, as well as East Timor—the historically famous "spice islands" of the Moluccan Archipelago—the Solomon Islands, and, of course, New Guinea. Telnov has begun a new book series, entitled Biodiversity, Biogeography and Nature Conservation in Wallacea and New Guinea, that aims to compile and highlight new research in the region, focusing both on biology and conservation. The first volume, currently available, also includes the description of 150 new species.
New frog trumps miniscule fish for title of 'world's smallest vertebrate'
(01/12/2012) How small can you be and still have a spine? Scientists are continually surprised by the answer. Researchers have discovered a new species of frog in Papua New Guinea that is smaller than many insects and dwarfed by a dime. The frog trumps the previously known smallest vertebrate—a tiny fish—by nearly 1 millimeter.
As Amazon deforestation falls, food production rises
(01/09/2012) A sharp drop in deforestation has been accompanied by an increase in food production in the Brazilian state of Mato Grosso, reports a new study published in the journal Proceedings of the National Academy of Science. The research argues that policy interventions, combined with pressure from environmental groups, have encouraged agricultural expansion in already-deforested areas, rather than driving new forest clearing.
Evidence mounts that Maya did themselves in through deforestation
(12/08/2011) Researchers have garnered further evidence for a smoking gun behind the fall of the great Maya civilization: deforestation. At the American Geophysical Union (AGU) conference, climatologist Ben Cook presented recent research showing how the destruction of rainforests by the Mayan ultimately led to declines in precipitation and possibly civilization-rocking droughts. While the idea that the Maya may have committed ecological-suicide through deforestation has been widely discussed, including in Jared Diamond's popular book Collapse, Cook's findings add greater weight to the theory.
More news on rainforest agriculture
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