Causes of Deforestation: Direct Causes

People have been deforesting the Earth for thousands of years, primarily to clear land for crops or livestock. Although tropical forests are largely confined to developing countries, they aren’t just meeting local or national needs; economic globalization means that the needs and wants of the global population are bearing down on them as well. Direct causes of deforestation are agricultural expansion, wood extraction (e.g., logging or wood harvest for domestic fuel or charcoal), and infrastructure expansion such as road building and urbanization. Rarely is there a single direct cause for deforestation. Most often, multiple processes work simultaneously or sequentially to cause deforestation.

The single biggest direct cause of tropical deforestation is conversion to cropland and pasture, mostly for subsistence, which is growing crops or raising livestock to meet daily needs. The conversion to agricultural land usually results from multiple direct factors. For example, countries build roads into remote areas to improve overland transportation of goods. The road development itself causes a limited amount of deforestation. But roads also provide entry to previously inaccessible—and often unclaimed—land. Logging, both legal and illegal, often follows road expansion (and in some cases is the reason for the road expansion). When loggers have harvested an area’s valuable timber, they move on. The roads and the logged areas become a magnet for settlers—farmers and ranchers who slash and burn the remaining forest for cropland or cattle pasture, completing the deforestation chain that began with road building. In other cases, forests that have been degraded by logging become fire-prone and are eventually deforested by repeated accidental fires from adjacent farms or pastures.

Tropical Deforestation
• Introduction & Impacts of Deforestation
• Climate Impacts
• Causes of Deforestation
• NASA Tropical Deforestation Research
• Sustaining Tropical Forests
• References

Although subsistence activities have dominated agriculture-driven deforestation in the tropics to date, large-scale commercial activities are playing an increasingly significant role. In the Amazon, industrial-scale cattle ranching and soybean production for world markets are increasingly important causes of deforestation, and in Indonesia, the conversion of tropical forest to commercial palm tree plantations to produce bio-fuels for export is a major cause of deforestation on Borneo and Sumatra.

In densely populated central Africa, small subsistence plots cover the once-forested hillsides. (Photograph ©2006 Stefan Gara.)

Underlying Causes

Although poverty is often cited as the underlying cause of tropical deforestation, analyses of multiple scientific studies indicate that that explanation is an oversimplification. Poverty does drive people to migrate to forest frontiers, where they engage in slash and burn forest clearing for subsistence. But rarely does one factor alone bear the sole responsibility for tropical deforestation.

State policies to encourage economic development, such as road and railway expansion projects, have caused significant, unintentional deforestation in the Amazon and Central America. Agricultural subsidies and tax breaks, as well as timber concessions, have encouraged forest clearing as well. Global economic factors such as a country’s foreign debt, expanding global markets for rainforest timber and pulpwood, or low domestic costs of land, labor, and fuel can encourage deforestation over more sustainable land use.

On the southern margin of the Amazon, in the state of Mato Grosso, Brazil, huge expanses of rainforest are being cleared by industrial soybean, sugar cane, and maize producers. (Photograph ©2006 Guido van der Werf, Vrije Universiteit, Amsterdam.)

Access to technology may either enhance or diminish deforestation. The availability of technologies that allow “industrial-scale” agriculture can spur rapid forest clearing, while inefficient technology in the logging industry increases collateral damage in surrounding forests, making subsequent deforestation more likely. Underlying factors are rarely isolated; instead, multiple global and local factors exert synergistic influences on tropical deforestation in different geographic locations.

Rates of Tropical Deforestation

Several international groups produce routine estimates of tropical deforestation, most notably the Food and Agriculture Organization (FAO) of the United Nations, which has been producing a global forest resources assessment every five to ten years since the late 1940s. The FAO report is based on statistics provided by countries themselves, and because the ability of countries to accurately assess their forest resources varies depending on their financial, technological, and institutional resources, the estimates for some countries are likely more accurate then others. Many countries use satellite imagery as the basis for their assessments, and a few research teams have used satellite data as the basis for worldwide estimates of tropical deforestation in the 1980s and 1990s.

Some scientists and conservationists argue that the FAO provides too conservative an estimate of rates of deforestation because they consider any area larger than one hectare (0.01 square miles) with a minimum tree cover of 10 percent to be forested. This generous definition of “forest” means that a significant amount of degradation can occur before the FAO categorizes an area as deforested. On the other hand, some satellite-based studies indicate deforestation rates are lower than even the FAO reports suggest. In the FAO’s most recent forest assessment report, published in 2005, the organization itself revised downward the deforestation rates for the 1990s that it reported in 2001. Despite revisions and discrepancies, the FAO assessment is the most comprehensive, longest-term, and widely used metric of global forest resources.

In addition to local factors, international trends drive deforestation. The expansion of palm oil plantations in Indonesia and Malaysia is a response to high petroleum prices and, ironically, to an increasing global demand for bio-fuels perceived to be “green.” (Photograph ©2006 Badly Drawn Dad.)

All tropical forest sub-regions (coded by color) are represented in a list of the top 20 countries that cleared the most forest between 1990 and 2005. Brazil, the leader, cleared over 42 million hectares, an area the size of California. (Graphic by Robert Simmon, based on data provided by individual countries to the U.N. Foreign Agricultural Organization for the Global Forest Resources Assessment Report 2005.)

The FAO report does not compile statistics for tropical forest regions as a whole, but the country-by-country and regional-scale statistics provide a grim picture. The scope and impact of deforestation can be viewed in different ways. One is in absolute numbers: total area of forest cleared over a certain period. By that metric, all three major tropical forest areas, including South America, Africa, and Southeast Asia, are represented near the top of the list. Brazil led the world in terms of total deforested area between 1990 and 2005. The country lost 42,330,000 hectares (163,436 square miles) of forest, roughly the size of California. Rounding out the top five tropical countries with the greatest total area of deforestation were Indonesia, Sudan, Myanmar, and the Democratic Republic of Congo.

Although all major tropical forest sub-regions (coded by color) are represented in a list of the top 20 countries that cleared the largest percentage of their forests between 1990 and 2005, African countries (blue bars) dominate, beginning with Comoros, a small island nation north of Madagascar. (Graphic by Robert Simmon, based on data provided by individual countries to the U.N. Foreign Agricultural Organization for the Global Forest Resources Assessment Report 2005.)

Another way to look at deforestation is in terms of the percent of a country’s forest that was cleared over time. By this metric, the island nation of Comoros (north of Madagascar) fared the worst, clearing nearly 60 percent of its forests between 1990 and 2005. Landlocked Burundi in central Africa was second, clearing 47 percent of its forests. The other top five countries that cleared large percentages of their forests were Togo, in West Africa (44 percent); Honduras (37 percent); and Mauritania (36 percent). Thirteen other tropical countries or island territories cleared 20 percent or more of their forests between 1990-2005.

 NASA Tropical Deforestation Research
 Climate Impacts