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Amazon rainforest case study (water and carbon cycles) - Coggle Diagram
Amazon rainforest case study (water and carbon cycles)
Carbon
The UFZ estimated that the Amazon stored 76 billion tonnes of carbon in 2019.
It forms a carbon sink of 1-3 GtC/year. Estimated that in 2019 the Amazon absorbed around 600 million tonnes per year
Forests have been increasing its above-ground biomass by 0.3-0.5% per year
Rising productivity of tropical forests is due to increasing C02 concentrations in the atmosphere
An increase in atmospheric CO2 lead to a growth spurt for the Amazon’s basin’s trees; however the growth stimulation feeds through the system, causing trees to live faster and die younger, causing a surge in the rate of trees that are dying in the Amazon
16,000 tree species, 182 dominating the carbon storage process
Water
Additional water evaporates from the ground and rivers or is released into the atmosphere by transpiration from plant leaves
Average rainfall across the Amazon basin is approximately 2,300mm annually, but in some areas of the north-western side it can exceed 6,000mm
The average discharge of water into the Atlantic Ocean by the Amazon is approximately 175,000 m3/s, or around 15% of the fresh water entering the oceans each day
The Rio Negro, a tributary of the Amazon, is the second largest river in the world in terms of water flow, and is 100m deep and 14km wide near its mouth at Manaus, Brazil
Half the rainfall never reaches the ground; intercepted by the forest canopy and re-evaporated into the atmosphere; about 48% of this falls again as rain; 30% of the rainfall actually reaches the sea; the rest being caught up in the constant closed system loop
It is thought that the water cycle of the Amazon has global effects. The moisture created by rainforests travels around the world. Moisture created in the Amazon ends up falling as rain as far away as Texas, and forests in Southeast Asia influence rain patterns in south eastern Europe and China. 4
When forests are cut down, less moisture goes into the atmosphere and rainfall declines, sometimes leading to drought. These have been made worse by deforestation. 4
Drivers of change
Between 2000 and 2007, the Brazilian Amazon was deforested at a rate of 19,368km2 per year (an area larger than Greece)
Brazil is the worlds 4th largest climate polluter, 75% of the greenhouse gas emissions are attributed to deforestation and land use change; 59% of this is from loss of forest and burning in the Amazon
The removal of forest was done using slash and burn techniques:
Reduces the retention of humidity in the soil’s top layer down to a depth of 1m
Facilities sudden evaporation of water previously retained in the forest canopy
Increases albedo and temperature
Reduces porosity of soil, causing faster rainfall drainage, erosion and sitting of rivers and lakes
Any moisture that evaporates from deforested areas forms shallow cumulous clouds which usually do not produce rain
Forest emit salts and organic fibres along with water when they transpire. These act as a condensation nuclei and assist cloud formation and rain formation. Their loss inhibits the formation of clouds and reduce rainfall
If destroyed, the vast carbon store will be released into the atmosphere
There are a number of differences between tropical rainforests and the pasture land it is replaced with:
Forests absorb approximately 11% more solar radiation
Average temperature for rainforests = 24.1 degrees celcius
pasture is 33 degrees celcius
Temperature underneath the soils of the rainforest = 2.8 degrees celcius
temperature underneath the pasture = 8 degrees Celsius
Moisture content in the upper 1m of pasture soil is around 15% less than nearby forests
Deeper soil roots can pump more soil moisture to the surface, producing 20-30% more air humidity and consequently 5-20% more precipitation than pastures
Facts (PLC)
1000 species of bird
60,000 species of plants
10 million insects
Home to 20 million who cut down trees for farms and cattle
2.1 million square miles of land
Home to 20% of earths species
Rainforest area the size of Belgium is being cut down and burnt down every year
Change to the water and carbon cycles in the Amazon
Agriculture (to grow crops like Soya or Palm oil) or for pasture land for cattle grazing
Logging – This involves cutting down trees for sale as timber or pulp. The timber is used to build homes, furniture, etc. and the pulp is used to make paper and paper products. Logging can be either selective or clear cutting. Selective logging is selective because loggers choose only wood that is highly valued, such as mahogany. Clear-cutting is not selective. Loggers are interested in all types of wood and therefore cut all of the trees down, thus clearing the forest, hence the name- clear-cutting.
Road building – trees are also clear for roads. Roads are an essential way for the Brazilian government to allow development of the Amazon rainforest. However, unless they are paved many of the roads are unusable during the wettest periods of the year. The Trans Amazonian Highway has already opened up large parts of the forest and now a new road is going to be paved, the BR163 is a road that runs 1700km from Cuiaba to Santarem. The government planned to tarmac it making it a superhighway. This would make the untouched forest along the route more accessible and under threat from development
Mineral extraction – forests are also cleared to make way for huge mines. The Brazilian part of the Amazon has mines that extract iron, manganese, nickel, tin, bauxite, beryllium, copper, lead, tungsten, zinc and gold!
Energy development – This has focussed mainly on using Hydro Electric Power, and there are 150 new dams planned for the Amazon alone. The dams create electricity as water is passed through huge pipes within them, where it turns a turbine which helps to generate the electricity. The power in the Amazon is often used for mining. Dams displace many people and the reservoirs they create flood large area of land, which would previously have been forest. They also alter the hydrological cycle and trap huge quantities of sediment behind them. The huge Belo Monte dam started operating in April 2016 and will generate over 11,000 Mw of power. A new scheme the 8,000-megawatt São Luiz do Tapajós dam has been held up because of the concerns over the impacts on the local Munduruku people
Settlement & population growth – populations are growing within the Amazon forest and along with them settlements. Many people are migrating to the forest looking for work associated with the natural wealth of this environment. Settlements like Parauapebas, an iron ore mining town, have grown rapidly, destroying forest and replacing it with a swath of shanty towns. The population has grown from 154,000 in 2010 to 220,000 in 2012. The Brazilian Amazon’s population grew by a massive 23% between 2000 and 2010, 11% above the national average.
The impacts of deforestation
Atmospheric impacts
Deforestation causes important changes in the energy and water balance of the Amazon. Pasturelands and croplands (e.g. soya beans and corn) have a higher albedo and decreased water demand, evapotranspiration and canopy interception compared with the forests they replace.
Lathuillière et al. 10 found that forests in the state of Mato Grosso;
• Contributed about 50 km3 per year of evapotranspiration to the atmosphere in the year 2000.
• Deforestation reduced that forest flux rate by approximately 1 km3 per year throughout the decade.
• As a result, by 2009, forests were contributing about 40 km3 per year of evapotranspiration in Mato Grosso.
In Rondônia, Brazil, one of the most heavily deforested areas of Brazil, daily rainfall data suggest that deforestation since the 1970s has caused an 18-day delay in the onset of the rainy season
SSE Amazon also has many wild fires, which are closely associated with deforestation, forest fragmentation and drought intensity
The impacts of climate change on the Amazon
Some Amazon species capable of moving fast enough will attempt to find a more suitable environment. Many other species will either be unable to move or will have nowhere to go.
Higher temperatures will impact temperature-dependent species like fish, causing their distribution to change.
Reduced rainfall and increased temperatures may also reduce suitable habitat during dry, warm months and potentially lead to an increase in invasive, exotic species, which then can out-compete native species.
Less rainfall during the dry months could seriously affect many Amazon rivers and other freshwater systems.
The impact of reduced rainfall is a change in nutrient input into streams and rivers, which can greatly affect aquatic organisms.
A more variable climate and more extreme events will also likely mean that Amazon fish populations will more often experience hot temperatures and potentially lethal environmental conditions.
Flooding associated with sea-level rise will have substantial impacts on lowland areas such as the Amazon River delta. The rate of sea-level rise over the last 100 years has been 1.0-2.5 mm per year, and this rate could rise to 5 mm per year.
Sea-level rise, increased temperature, changes in rainfall and runoff will likely cause major changes in species habitats such as mangrove ecosystems
Impact of deforestation on soils
Removing trees deprives the forest of portions of its canopy, which blocks the sun’s rays during the day, and holds in heat at night. This disruption leads to more extreme temperature swings that can be harmful to plants and animals. 8 Without protection from sun-blocking tree cover, moist tropical soils quickly dry out.
In terms of Carbon, Tropical soils contain a lot of carbon. The top meter holds 66.9 PgC with around 52% of this carbon pool held in the top 0.3 m of the soil, the layer which is most prone to changes upon land use conversion and deforestation
Deforestation releases much of this carbon through clearance and burning. For the carbon that remains in the soil, when it rains soil erosion will wash much of the carbon away into rivers after initial deforestation and some will be lost to the atmosphere via decomposition too.
Impacts of deforestation on rivers
When trees are removed this cycle is severely disrupted and areas can suffer more droughts
There is increased soil erosion and weathering of rainforest soils as water acts immediately upon them rather than being intercepted.
Flash floods are more likely to happen as there is less interception and absorption by the forest cover.
Conversely, the interruption of normal water cycling has resulted in more droughts in the forest, increasing the risk of wild fires
More soil and silt is being washed into rivers, resulting in changes to waterways and transport
Disrupt water supplies to many people in Brazil