History and Biology of Slash and Burn in the Amazon

(WWF 2013)

Slash and burn agriculture is a technique used by many people and corporations to grow food crops in areas of dense vegetation, land with a small amount of nutrients, or places full of pests (Stief 2008).  The process consists of cutting down trees and some vegetation and burning the remaining plants and animals in the area. The purpose of slash and burn is to clear the land for farming and to release the nutrients in vegetation back into the infertile soil to make it fertile. Food crops are then planted, using the ashes to provide nutrients for the crops (Stief 2008).  Food can be planted until the land is no longer fertile, at which point the farmers move on to another plot of land as they wait several years for vegetation to grow back in that area (Stief 2008).

In the Amazon, this form of agriculture has been around for thousands of years, starting with the indigenous people who, in addition to hunting, used small areas of the land just for subsistence farming - planting only as much food as they needed to live (EWA 1996).  Then, in the late 1900s, governments in tropical nations encouraged the poor to move out of urban areas and into the forests (Butler 2012).  They allowed people to clear the land for free ownership of parts of the forest (Butler 2012).  The method of slash and burn was not problematic on a small scale when less of the rain forest land was used; farmers could also wait for vegetation to regrow and the region's biodiversity to re-establish itself , but as more people began using slash and burn, it affected the environment negatively. The vegetation does not have enough time to grow back after each burn session, and the biodiversity in the environment is being lost; thus, some soil is being permanently damaged and remains infertile (Stief 2008). 

Soil within tropical rainforests like the Amazon is highly infertile despite its large biomass (Freedman 2008). This infertility is due to the great age of rainforests, the large amounts of precipitation that causes nutrient loss, and the warm humid climate that causes the soil to retain very little organic nutrients; as a result, most of the nutrients are bound up in living vegetation, mainly trees (Freedman 2008). However, when trees are burned during slash-and-burn agriculture the resulting ash causes an increase in nutrient availability, but this a short-lived process (Freedman 2008). Most of the nutrients are washed away, causing farmers to move on and repeat this process with another patch of land (Freedman 2008). Usually a plot of land that undergoes slash and burn needs time to fallow—at least over 5 years—but with growing populations and food needs, land is not being given enough time to fallow before it undergoes slash and burn again (Our Future Plant 2010). In many cases, if land continues to undergo slash and burn continually, soils can undergo laterization in which minerals are almost completely washed from the soil (Freedman 2008). Once this happens plots of land cannot be farmed and can be left degraded for centuries (Freedman 2008). Consequently, this also destroys the forest’s biodiversity and causes great waves of extinction (Freedman 2008).

Slash and burn also greatly affects climate change. As trees burn, large amounts of CO₂ is released into the air (RAN 2011). These gases are trapped in the atmosphere and prevent heat form leaving, raising Earth’s temperature (Chang 2007). Brazil is the fourth largest contributor to pollution in the world and unlike many of its fellow nations whose pollution comes from power plants and factories, 75% of Brazil’s greenhouse emission are due to the clearing and burning of forests (RAN 2011). 

Since the late 20^th century, governments, especially those in tropical areas, have recognized the ecological dangers of slash and burn agriculture, and have begun to take a stand alongside environment conservationists against the practice. In the 1980s, the Brazilian government has acknowledged that environmental degradation poses a threat to its human population as well as its biodiversity. About one fifth of the Amazon rainforest has disappeared due to deforestation (Chang 2007). As a result of the demand and high price for illegal timber, a chunk of forest about the size of Connecticut disappears because of the activities of subsistence farmers, illegal loggers, and corporations seeking to make a profit or survive off of the Amazon’s natural resources (Chang 2007). In order to make the soil more fertile for crops and collect timber; subsistence farmers, illegal loggers, and corporations use the method of slash and burn to clear the forest vegetation and make the soil more fertile (Chang 2007). Unfortunately, such level of deforestation can result in devastating effects, especially to Brazil’s southern region where much of the country’s agriculture, industry, and population is located (Chang 2007). Fortunately, the Brazilian government has recognized the severity of deforestation and has cracked down on the illegal activities of loggers, corporations, and farmers. Consequently, the expansion of national parks and biological reserves as well as increased government enforcement enabled Brazil to reduce deforestation: since 2004, the rate of deforestation in the Amazon decreased by 80% (Butler 2012b).

Butler, R. A., (2012) Deforestation in the Amazon. Mongabay.com. ( Date Accessed: May 17, 2013.) http://www.mongabay.com/brazil.html

Butler, R. (2012) Subsistence Agriculture and Deforestation. Tropical Rainforests. Mongabay.com. (Date

of Access: May 13, 2013.) http://rainforests.mongabay.com/0804.htm

Chang, J. (2007) As Brazil’s Rain Forest Burns Down, Planet Heats Up.  http://www.mcclatchydc.com. McClatchy Newspapers.  (Date Accessed: May 12, 2013.)

http://www.mcclatchydc.com/2007/09/08/19533/as-brazils-rain-forest-burns-down.html#.UY_TuLWcfTo

(EWA) Educational Web Adventures. (1996) Making a Living in the Amazon. Educational Web Adventures. (Date Accessed: May 9, 2013.) http://www.eduweb.com/agriculture/ag1.html

Freedman, B.(2008) Slash-and-Burn Agriculture. www.find.galegroup.com. Gale Cengage Learning. (Date Accessed: May 12, 2013.) http://find.galegroup.com/srcx/retrieve.do?sgHitCountType=None&sort=Relevance&prodId=DC&tabID=T001&subjectParam=Locale%2528en%252C%252C%2529%253AFQE%253D%2528su%252CNone%252C15%2529slash%2Band%2Bburn%2B%2524&resultListType=RESULT_LIST&searchId=R1&displaySubject=&searchType=BasicSearchForm&currentPosition=1&qrySerId=Locale%28en%2C%2C%29%3AFQE%3D%28SU%2CNone%2C15%29slash+and+burn+%24&subjectAction=DISPLAY_SUBJECTS&inPS=true&userGroupName=wall96493&sgCurrentPosition=0&contentSet=GSRC&docId=EJ2644042095&docType=GSRC

Our Future Planet. (2010) Slash and Burn Farming. Un-redd.org. UN-REED Programme. (Date Accessed: May 12, 2013.)  http://www.un-redd.org/AboutUN-REDDProgramme/tabid/102613/Default.aspx

(RAN) Rainforest Action Network. (2011) What is Agribusiness ?. Ran.org. Rainforest Action Network. (Date Accessed: May 12, 2013) http://ran.org/what-agribusiness .

Stief, C. (2008) Slash and Burn Agriculture. Geography. About.com. (Date of Access: May 9, 2013.)

http://geography.about.com/od/urbaneconomicgeography/a/slashburn.htm