The amazon Rainforest is one of the richest areas on Earth biodiversity wise and possesses many endemics species of fauna and flora. The Amazon also plays an human population has grown, and demands in soybeans, cattle and wood as increased over time, the Amazon rainforest has been selected for deforestation. Recent concerns have arisen over the last decades emphasizing the problems deforestation causes especially biologically. This problem has been further underlined as concerns over global climate change have arisen. The Amazon forest is the greatest tropical forest in size as it covers an area over seven million square kilometres and is found in ten countries of South America.
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– Motives of deforestation, rates, history
Most of the Amazon Basin ( >70%) is found in Brazil ; therefore most of our study will focus on the Brazilian Amazon. Starting in the late 1950’s, for the purpose of developing the western and northern parts of Brazil many new roads were constructed which constituted a direct access to the Amazon tropical forest. The construction of these routes along with other incentives ( such as cattle ranching , hydro electric project, timber extraction) was aimed at expanding development and integrating the whole territory into the country’s economy. The program was successful as people moved along these large highways; for example 2 million people moved along the Belem-Brasilia in the first 20 years of its construction. The settlement along the major highways and within the Amazon forest was highly unorganized which led to long term unnoticed deforestation.
Overtime the rates of deforestation have increased from the 1970’s to the 2003-2004 and since then have decreased. The peak in 2002-2004 was the highest rate of forest clearing for a three year period: 52 670 km² were cleared. The 2008-2009 area cleared totalizes for 7008 km².
The literature seems to agree on the motives for deforestation although the importance of small farmers in the process is debated . ( K.R Birby , P. Fearnside). The motives for deforestation are multiple: contrarily to common belief, the biggest reason behind clearing in cattle ranching secondly, is small farmer exploitation then, logging, and recently soybean and palm oil plantations have led to deforestation. The reason behind this hierarchy and cattle ranching as being the number one reason behind forest clearing is due to multiple state incentives. These incentives made cattle ranching one of the few profitable product to rise in the Amazon. Under the Brazilian law, clearing the land in order to install pasture is characterised as “effective”. (K.R Kirby). Cattle ranching is one of the most popular use of land in the Amazon as it is not a labour intensive job , by products can be used ( such as milk) , and it is produces offspring. Compared to crops, the main advantage of cattle ranching is that cattle ranching are independent of weather conditions.
Small farmers also play an important role in the clearing of the land as they apply slash and burn method in order to create fertile land to grow their crops on. As farmers need for more land, they continuously increase their property. K.R Kirby has calculated that on average a small farmer clears 1 ha of forest per year. Furthermore, tropical soils are not fertile and fail at the long term production of crops, thus after 2-3 years the land is unusable and new land has to be slashed and burned.
Today as agricultural financing has been more readily available in the Amazon compared to other regions in Brazil, soybeans farmers are pushing to the North. As the price for soybean has increased, it has become one of the most profitable crops to plant in the Amazon. A large part of the soybean production is used for export (as foreign currency) therefore greatly encouraged by the state which even plans on building new roads and infrastructure in order to expand the production.
Although not broadly mentioned in the literature, it is important to also underline the logging activities undergoing in the Amazon. JA Foley et al mention that the logging has recently been recognized as one major source of land change in the Amazon. Although selective logging is comparatively not as ecologically destructive as cattle grazing or pasture, it has been shown that logging destroyed the same amount of forest as the area cleared for other activities. Indeed, selective logging leaves behind a fraction of the natural forest and allows some natural regeneration; not completely destroying the ecosystem.
– Biodiversity effects:
The clearing of thousands of km² of land is not at any cost. The Amazon is one the world’s richest zone in terms of biodiversity and number of endemic species. Being one of the largest forests in the world the tropical Amazon forest constitutes an important carbon sink for the integrity of the planet. Scientists have become aware of the importance of conserving the forest because of the numerous ecosystem services it provides.
It is difficult to understand and quantify the ecosystem services provided by an ecosystem. As Fearnside explains, it is complicated to put a value on an ecosystem service. An obvious way of calculating the value of the ecosystem is using the profit of the good produced in the given area. This method does not take into account the future damage that could occur due to the abuse of the ecosystem. Indeed we taking the example of forest clearing , we can use the value of the good which will be produced on the area cleared but on a large scale that value does not take into account the habitat destruction of species. Often times we put a price on ecosystem services in order to emphasize the urgency of taking conservation actions, putting fines on illegal land used.
Based on the literature there are many ecosystem services provided by the Amazon rainforest. Namely the most important ecosystem services are carbon sequestering, water flow of the Amazon River, air circulation patterns, the spread of water borne disease , fires , invasion by exotic species and most importantly , and biodiversity loss.
The clearing of Amazon might influence the hydrological regime of the area because the forest regulates the quantity of water flowing into the river as well as the nutrient content. The quantity of water increases greatly overall because there is no interception by plants leading to much more surface runoff and less percolation in the soil. Indeed it has been observed in the Tocantins river basin, the changes during the 30 years period (1960-1990) in land cover have led to an approximate 25% increase in the river discharge during the same period although there were no changes in the precipitation regime. Over the long term, scientists are worried that the evaporation budget will change so much as to change global patterns of air circulation.
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Vector-borne diseases increase due to the loss of vegetation and due to an increase in the number of mosquitoes (which are common vectors of diseases). Forested areas allow for more control of the disease though population control of infected animals, their hosts and intermediate disease vector. In South America, the most important disease transmitted by mosquitoes is malaria. A study in Peru has shown that Anopheles darling mosquito species are more susceptible to biting as the land cover decreases. The study found that when the area is deforestated by more than 20%, mosquitoes have a tendency to bit more than in forested areas. The reason for this increase is due to the preference of mosquitoes to breed in areas with shrubs or grasslands. ( A.M. Vittor)
One of the most striking effects on deforestation is the loss of biodiversity. No papers truly estimated the loss of biodiversity due to deforestation. But based on the literature we can estimate the number of species potentially targeted by deforestation. The Brazilian Amazon is classified as one of the five megadiversity countries by the WWF (World Wild Fund) (P.Fearnside). Brazil has over 50 000 angiosperm plant species, over 400 species of mammals, over 1500 species of birds, over 500 species of amphibians, over 400 species of butterfly and over 70 species of reptiles. Deforestation can lead to changes in biodiversity’s ecological niches, habitat fragmentation, or even invasion of exotic species.
A major concern has arisen amongst ecologists due to the threat of deforestation on biodiversity hotspots. Indeed it has been observed in some cases that biodiversity hotpsots overlap the “deforestation hotpsots”. These latter are areas where deforestation occurs suddenly, locally and greatly pushed by demographic factors. The danger for the ecosystems when these two hotspots overlap is the extensive loss of habitat for the fauna and flora. Indeed, deforestation hotspots lead to much habitat fragmentation as many harvesters carry on their activity without much knowledge on the ecosystem and the implications of deforesting (Etter et al 2006). Moreover, it has been proven that a threshold exists for a species to survive. Species need enough area in order to reproduce and forage without it a population cannot sustain and is determined to extinguish. Much of the deforestation trends are not managed and very spontaneous, leading to patches of deforested land and often times the minimum threshold is surpassed threatening the survival of many generations. As underlined in Etter et al., no significant studies have been consolidated in order to better understand the overlapping of deforestation and biodiversity hotspots; suggesting more data to be collected. Indeed without data there cannot be any consensus on the conversation policies to protect the Amazon’s ecosystem. Another paper also suggests the idea that better inventories should be complied in order to understand the forest’s composition and to better manage the area based on the species’ autoecology. Furthermore the paper underlines the importance of thorough and precise data entries with identical quantification measurements. These factors are all very important in the inventory process in order to build credible dataset on which policy makers can rely upon (Biscaia de Lacerda 2010).
– Deforestation in the context of Global Climate Change
A major concern of the 21st century is the increase of carbon dioxide in the atmosphere and the consequences on the world’s biomes. The role of the Amazon forest in the global carbon cycle is storage of organic carbon in the soil or in plants. The process through which plants take in CO2 is photosynthesis storing it afterwards in the biomass under the form of leaves, branches, roots, flowers and other structural tree components. The destruction of the Amazon makes it an emitter of carbon rather than a sink. Indeed because of land cover changes, carbon is no longer stored. Per se, carbon is not emitted from the forest rather carbon is not taken up by the trees anymore resulting in a net surplus of CO2 levels in the atmosphere. Furthermore the necessary machinery used for deforestation as well as the by-products of wood and the processing of trees in factories also contribute to increased levels of carbon dioxide in the atmosphere.
Some studies have tried to understand the changes which would occur if CO2 levels increased and deforestated areas kept increasing. The outcome results in many effects linked to changes in surface albedo, leaf area index, and surface roughness and texture (Compounding). In the study, the CO2 levels were doubled, increasing the CO2 concentration to 660 ppm. The IPCC’s projection on CO2 levels project that 660 ppm will be reached by the end of the century under the least severe scenario: A1B which predicts: “A future world of very rapid economic growth, low population growth and rapid introduction of new and more efficient technology. Major underlying themes are economic and cultural convergence and capacity building, with a substantial reduction in regional differences in per capita income. In this world, people pursue personal wealth rather than environmental quality.” ( IPCC – http://www.ipcc-data.org/ddc_co2.html). The sole effect of doubling CO2 concentration in the atmosphere results in a 2.6 T°C increase in temperature, increase in precipitation by 9.0 mm per month , and increase in -the net longwave radiation at the landsurface by 4.5 W m-² subsequently increasing the surface evapotranspiration. There is not a great difference for all the factors when studying the present deforestation climate with the future warmed climate combined with deforestation, directly pointing to the fact that deforestation is the main source of deregulation in the climate (Figure 2). Indeed most changes due to increased CO2 levels are felt in the mid-high latitudes.
Figure 2( Zhang et al.)
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