The Amazon Rainforest
- Cameron Lock
- Feb 11, 2023
- 7 min read
Updated: Mar 11, 2023
Location
The Amazon rainforest is located on the continent of South America and spans the nations of Brazil, Bolivia, Peru, Ecuador, Columbia, Venezuela, Guyana, French Guiana and Suriname. It is located 3.4653 degrees south of the equator.
Introduction
The Amazon Rainforest is the world's largest tropical rainforest covering 1.4 billion acres. It has a very rich biodiversity as it is home to one-tenth of the known species of plants and animals. Running through the rainforest is the Amazon River, one of the longest rivers on earth, second only to the river Nile, this river holds a record discharge of 209,000 metres cubed per second. Contained within the Amazon is an incredibly vast number of trees which absorb CO2 for photosynthesis and sequester (release) this when they die, this amongst other reasons previously mentioned are why it plays an important role in both the biological and global water and carbon cycles. However, the amazon is experiencing horrific levels of deforestation with one and a half acres being destroyed a second, this occurs at such a high rate that in a mere 40 years the Amazon has gone from occupying 14% of the earth's surface to now only 6%.
Climate
The average annual rainfall across the whole amazon basin is 2300 mm a year, this is a huge amount and is as a result of many factors. Firstly half of the amazon's rainfall is provided by eastern trade winds from the amazon. The second of which is the amazon's equatorial latitude which therefore means it receives lots of incoming solar radiation (insolation), this leads to very high temperatures (annually averaging 25 degrees Celsius) but this can reach or even breach 40 degrees Celsius). High temperatures can lead to high levels of evaporation and photosynthesis leading to higher evapotranspiration; this means much more water is stored in the atmosphere. This combined with the amazon's low pressure air means that there is a very high humidity (88% in the wet season and 77% in the dry season) this causes high levels of condensation and as a result precipitation. Furthermore dissolved (ions from plants) in water cause high condensation and thus high rainfall.
However, only half of this rainfall actually reaches the surface; the rest is intercepted by the canopy and is either absorbed by plants in the biosphere or evaporated. To add to this only 30% of all rainfall actually reaches the sea, the rest is kept in a closed loop, this is likely as a result of the dense vegetation absorbing or intercepting water so it takes more time to reach water courses then take water to the sea.
This shows the massive affect the biosphere has on the climate of the amazon as it controls evapotranspiration and the flow of water weather this be through intercepting rainfall so it does not reach water courses so fast as is instead absorbed and transpired or by trapping the water in the canopy so it is exposed to more sunlight so more evaporation.
However the Amazons climate is at a massive risk of change, this is as a direct result of deforestation which can hugely alter the amazon's biosphere which can lead to upsetting the dynamic equilibrium of the amazon's system and can cause a variety of undesirable feedback loops.
Carbon in The Amazon
Due to the immense amount of vegetation in the Amazon it stores 80 to 120 billion tonnes of carbon, a large amount of this would be stored in the biosphere as biomass or stored by plants for photosynthesis to create glucose (a vital simple sugar that is synthesised in respiration to produce ATP). As a result the amazon is known as a Carbon sink due to the sheer amount of CO2 it absorbs (1-3GtC/year) for photosynthesis. This has a great global importance as this means anthropogenic Carbon Dioxide can be absorbed as opposed to partaking in the accelerated greenhouse effect thus slowing global warming. However, when trees die stored carbon dioxide is released into the atmosphere where it is able to act as greenhouse gas. This is the reason deforestation in the Amazon is a global threat as if along proportion of the Amazon is lost then there will be major disruptions to the global carbon cycle as there could be billions of tonnes of CO2 in the atmosphere released from the cutting down of Amazon trees and this is unable to be reabsorbed by the Amazon as the replacement vegetation cannot absorb as much carbon. Furthermore the loss of such a large Carbon sink means Carbon dioxide is not absorbed from the atmosphere to the biosphere as a result there is a higher concentration of greenhouse gases in the atmosphere which could speed up global warming and have devastating effects on the earth and humanity.
Deforestation in the Amazon
Deforestation in the Amazon occurs on an absolutely massive scale and at an alarmingly fast rate of one football pitch a second. So far 13.2% has been cleared, that is a quite frankly staggering amount, this level of sheer deforestation can cause devastating local and global effects. Deforestation can have terrible effects on the carbon cycle due the previously mentioned issue of trees releasing stored Carbon dioxide when they die, however, this is not the only problem caused by deforestation.
Agriculture
One of the major causes of deforestation is farming cattle for HIC based meat producers and other agricultural products. This accounts for a vast amount of deforestation. Cattle farming ,in my opinion, is the worst as the cattle excrete methane which is a stronger greenhouse gas than CO2 this means it has a much stronger warming effect this will dramatically accelerate the greenhouse effect. Cattle ranching is also responsible for an atrocious 80% of all deforestation in the Amazon.
The replacement of rainforest with pastureland can also cause massive problems especially in terms of changing the water cycle and climate of the Amazon. One such dilemma is that the upper one metre of pasture soil contains 15% less moisture than nearby forest as a result soil saturation is more likely to occur and so as a result surface runoff is more common and as a result more water goes into water courses as oppose to the biosphere and the lithosphere. This also increases flood risk. Furthermore, replacement plants cannot pump as much soil water to the surface this leads to 20%-30% less air humidity and as a direct result 5%-10% less precipitation this can starve the amazon of much needed water and can put the Amazon at further risk of drying up and becoming a savannah.
Mining
The Amazon has a wealth of minerals such as zinc and gold and as the nations around the Amazon NEEs and LICs (3rd world nations) they want to tap into these resources in order to further economic growth and create jobs for citizens. However this can have devastating consequences and huge amounts of the forest are cleared and large amounts of topsoil is removed which means plants cannot regrow and large amounts of wildlife is killed this can massively decrease biodiversity. Toxic chemicals used in mining may end up in water courses poisoning the underwater life.
Settlement and Urbanisation
People come to live in the Amazon in search of work in mines or agriculture.As a result of this urbanisation is rapid in 2010 there were 154,000 living in the Amazon in 2012 there were 220,000, that is a rise of 66,000 people in merely 2 years. This has caused a rapid rise in the building of shanty towns, for example, Parauapebas, an iron ore mining town.
Consequences of deforestation
Deforestation can have massive effects on the Amazon’s fragile water cycle and the flows that occur between each sphere. When deforestation is not extensive ( below 50%) evapotranspiration decreases as plants have smaller leaves and shallower roots so they cannot absorb as much water. As a result there is more surface runoff and throughflow, therefore, water reaches the river faster increasing discharge and lag time (time between peak discharge and peak rainfall) this leads to an increase in local flooding. If deforestation surpasses 50% the issue is exacerbated and a positive feedback loop ( this is when the effects of disrupting a system are amplified by the subsequent knock on effects) occurs. When this occurs, due to low evapotranspiration, water leaves the area via the river channel as opposed to staying in the forest’s system. This means there is less water vapour in the atmosphere so precipitation levels fall as a result less river enters the river channel so flow is reduced. This also means less water is transferred to the biosphere and upper lithosphere thus starving these areas of water. This may also have a devastating effect on those living in the Amazon as their supply of water is reduced.
Forest fires and draught
The clearing of the landscape results in increased amounts of droughts during the dry season,this meansplants andanimalswillhave low access to water for longer and more frequent periods as this mayput species ofwillife atrisk asthey donothavethe neccasary conditions to survive. Furthermore, the lack of water, higher temperature ground (caused by increased pasture land) and equatorial temperatures will increase risk of forest fires. This will be devasting as trees in the Amazon ,unlike other parts of the world do not have adaptations to withstand fire, such as thick bark and heat resistant seeds,as aresult trees will easily burn, thus causing the canopy to thin and dry dead woodto accumulat increasing the risk of another fire and the risk ofthe Amazon becoming a savannah.
Solutions
The Brazilian government is keen to introduce a land resgistry which hopefully could reduce illeagle logging and ranching by establishing clear property rights, however this will be very hard to enforce purely due to the sheer vastness of the Amazon.
Another method would be to encourage markets to purchase legally registered products however the markets are not eco-sensitive and will purchase the cheapest products.
Some argue that there should be expansion of national parks, this would protect from legall deforestation however it is still very difficult to police illegal ranchers and loggers who will clear areas of forest regardless of if it is or is not a national park.
One of the best methods is ecotourism which is when Amazon tourism is done in an ecofreindly way and teaches tourists about the Amazon’s ecosystem and its fragility. To add to this, it also provides jobs for locals aand benefits the Brazillian economy through money made from staff and business taxes.
One cause of deforestation is LICs attempting to relieve debt to HICs, as a result the REDD (reduced emissions from deforestation and forest degredation) believe the rich nations should pay the poor nations to not cut down trees. Consiquntly, following the copenhagen 2009 climate talks $4.5 billion was pledged to support this, and carbon tax is another way to raise rvenue without deforesting.
Conclusion
To conclude Amazon has an amzingly complex ecosystem full of different components ,biotic and abiotic, that interlink to form the vast and lushous forest. However this is at risk due to deforestation by the surrounding nations in order to develop their economys and the lives of their people. However this can have horrific effects on the rainforest and the world (as a result of the loss of a massive carbon sink and the potential carbon emmisions from deforestation) however governments are trying to fix this and there is still tiime to do so, although this time is running out.
Bibliography
AQA A Level Geography fourth edition, published by Hodder Education
Geography reveiw Thecarbon cycle and the Amazon
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