Topic 6: EQ3 Flashcards
What is land conversion?
Any change from natural ecosystems to alternative use; it usually reduces carbon and water stores and soil health.
Due to the growing demands for food, fuel and other resources, there have been contrasting regional trends for land conversion.
What deforestation is currently happening?
By 2015, 30% of all global forests had been completely cleared, and a further 20% was degraded.
What deforestation is occurring in Madagascar?
Since the 1950s, Madagascars tropical forests have been being clearing at a rapid rate by farmers, but also a growing international demand for Madagascar’s tropical hardwood. Debt repayments have also caused the government to encourage farmers to clear land to grow cash crops. 2/3 of Madagascars land has now been lost.
What are the main drivers of deforestation?
-Increasing demand for commodities production
-Soy, palm oil, beef and paper production
-Dams, reservoirs and other infrastructure construction
-Open cast mining
What is the impact of deforestation on the carbon cycle?
-Reduction in storage in soil and biomass, especially above ground (due to reduced leaf litter etc)
-Reduction in CO2 intake through photosynthesis flux
-Increased carbon influx to atmosphere by burning and decomposing vegetation
-Less soil and ground carbon also has affects on the geological carbon cycle.
What is the impact of deforestation on the water cycle?
-Infiltration is decreased
-Runoff and erosion are increased
-Flood peaks are higher and the lag time is shorter
-Increased discharge leads to flooding
-More eroded material is carried in the river, both as bed load and as silt and clay in suspension.
-Lack of evapotranspiration causes annual rainfall to be reduced
What are the impacts of deforestation on soil health?
-Raindrop impact washes finer particles of clay and humus away.
-Coarser and harsher sands are left behind
-CO2 is released from decaying woody material
-Biomass is lost, due to reduced plant growth/photosynthesis
-Rapid soil erosion leads to a loss of nutrients
-Increased leaching means that minerals are lost.
What is the impact of deforestation on the atmosphere?
-Turbulence is increased as the heated ground induces convectional air currents
-Oxygen content is reduced and transpiration rates are lower
-Reduced shading leads to more direct sunlight reaching the forest floor.
-Reduced evapotranspiration makes it less humid, also cause air to be drier
-Evapotranspiration rates from the resultant grasslands are about 1/3 that of the tropical rainforest.
What are the impacts of deforestation on the biosphere?
-Evaporation from vegetation is reduced
-Less absorption of CO2 means a reduced carbon store.
-Species diversity is reduced (less resilient forest plants die off)
-Ecosystem services are reduced
-Decrease in habitats means that fewer animal species survive
-Biomass is lost due to reduced plant growth/photosynthesis
What are the regional trends of deforestation?
-Temperate forests such as in the UK and USA have a long history of exploitation, 90% was deforested by the 19th century
-Boreal forests have been increasingly threatened since the mid-twentieth century, for example by oil and tar sands production in Russia and Canada.
-Tropical forests have lost half their area since 1960, especially in Africa and South America. This is mainly for raw material exploitation, timber logging and farming.
Why is the terrestrial biosphere so important?
The terrestrial biosphere sequesters about 1/4 of fossil fuel CO2 emissions annually, which directly slows down global warming.
What is afforestation?
This is the planting of trees on land that has never had forest, or has been without forest for a long time,
Reforestation, however, if where you plant trees in places with recent tree cover, replacing lost primary forests.
What are the costs and benefits of afforestation?
Although it is positive of CO2 sequestration and does counter most of the issues which surround deforestation , afforestation can cause some controversy, due to its impacts on landscape character, carbon water and soil systems.
Commercially planted trees will often store less carbon, use more water and are more disease prone. These issues are seen in China’s Three-North Shelterbelt Project to reduce desertification.
What is the grassland conversion?
Tropical and temperate grasslands cover 26% of global land area, and the changes from these grasslands to areas suitable for farming is being driven by rapid population growth, but also a change in African farming from nomadic (moving around constantly, giving vegetation a chance to regrow) to sedentary (staying in one area) farming.
Why can grasslands present ideal conditions for farming?
-Temperate grasslands have no trees and a seasonal growth pattern which relates to a wide annual temperature range. Some soils also contain chernozem making them very fertile, and these areas become especially vulnerable.
-The tropical grasslands do have scattered trees, and despite the soils often being infertile, land is still converted.
What are the disadvantages of converting grasslands to farm?
-The initial removal of grasslands releases CO2 from soils into the atmosphere
-Annual ploughing enables soil bacteria to release CO2
-Biofuel crops need carbon-based nitrogen fertiliser and chemical pesticides, so they produce a net increase in CO2 emissions
-Biofuel crops are heaving consumers of water, so they need irrigation which impacts groundwater stores (aquifers).
-Cultivated soils are liable to erosion by runoff and wind
-Natural habitats are reduced
-The ‘lung effect’ is reduced.
What is an example of grassland conversion?
In 2007-15, a biofuel ‘rush’ swept across Midwest America. The farmers were encouraged to grow corn, soya and rapeseed. Grasslands were ploughed up and over 5.5million hectares of natural grassland disappeared. The cause of this rush was to:
-Increase the amount of ethanol being used in petrol
-Boost the economies of rural US states.
-Reduce US dependence on overseas oil imports
-Reduce CO2 emissions from transport.
How does ocean acidification work?
1) The ocean absorbs CO2 from the atmosphere
2) The absorbed CO2 then breaks down to form unstable carbonic acid. In order to stabilise these, hydrogen ions are released.
3) This causes issues as these carbonate ions bond with hydrogen ions more easily than calcium ions. This forms bicarbonate ions, which reduces the concentration of carbonate ions.
4) These calcium carbonate ions are required by marine life to build and maintain calcium-based structures such as shells and coral. Ocean marine life growth is therefore limited.
What ocean acidification has occurred in recent times?
The worlds oceans are a major carbon sink, and they have absorbed about 30% of CO2 produced as a result of human activities since 1800. This ocean acidification has lowered the pH of the ocean by about 0.1 to a pH of 8.1. This has caused it to be about 30% more acidic than it was in 1750.
How does coral bleaching occur?
Corals get their colour from the algae that live in their tissues. The most important role of the algae is to provide the food to the coral through the carbohydrates produced during photosynthesis. Coral has a slim temp range which is works best within, never below 18°C, but ideally within 23-29°C. If it becomes too warm, then ocean corals turn white, and this is known as coral bleaching.
With the upper 75m of oceans warming by 0.11°C per decade between 1970-2010, corals are becoming increasingly at risk, and if coral pH drops below 7.8, the acidity could even cause the reefs to disintegrate entirely.
Why is the critical threshold of ocean acidity so important?
The critical threshold is the point of no return, which corals won’t be able to recover from if they went behind this point. This will cause effects such as affecting the ability of marine life to build shells and skeletons, so creating thinner or smaller shells and limiting coral reef building. The acidity will also reduce mineral availability, which means less corals lead to less habitats, and irreversible damage to the biodiversity and ecosystem productivity.
What impacts will be felt if coral reefs are destroyed?
They provide a crucial ecosystem service, and without corals….
-the shelter they provide for 25% of marine species will be lost.
-their ability to protect shorelines will be lost
-Fishing industries will be affected
-tourist income will be lost
What is the anthropogenic (human) impact on coral reefs?
Humans can impact corals through a number of ways, for example:
-Increase in carbon in local ecosystems through boat pollution
-Human waste on coastlines inputting foreign chemicals to oceans
-Harmful chemicals from sun cream being deposited in oceans near coastlines.
This human damage meant that for a period of time, Thailand’s Maya Beach was closed off from public use to revitalise their corals.
How have droughts in the Amazonia (South America) caused issues?
Droughts in the Amazon usually occur every 10 years, but in 2005 and 2010 there were too mega-droughts. In 2005, around 70million hectares of pristine mature forest was damaged, 30% of the total area. Changes could be seen visibly, in the canopy layer, with tree fall and dieback of branches.
What was the impact of the Amazon droughts on carbon?
-During these droughts, trees absorbed less CO2, and over a 6 month period photosynthesis slowed by 10%.
-The droughts also caused lots of dead, dry tree branch to fall to the ground. This caused a positive feedback cycle of carbon release due to the increased risk of wildfires.
-In 2005, the trees released 5billion tonnes of CO2, more than it received, meaning it was a carbon source rather than a sink.
How can soil damage from drought cause a loss of carbon stores?
-Degraded soils which lose organic matter and moisture have lesss ability to store carbon. When healthy, soils can store 3x the carbon vegetation can.
-Undisturbed peat-soil and wetland areas (covering 3% of the worlds land area) can be major carbon stores, but due to drainage and global warming their decomposition, respiration and fire risk has heavily increased. Although this can be reversed with the correct measures of restoration, it is all playing into the positive feedback cycle of droughts increasing atmospheric CO2.
What are shifting climate belts?
Climate change models are suggesting global weather patterns may be shifting, which results in permanent changes which make some world regions wetter and others drier. Some scientists regard the tropical rainforest issues may provide the scare needed to change human carbon usage, but the tipping point may be reached before this damage is reversed.
The THC could also be affected if greater precipitation or glacier melt causes causes freshwater to enter oceans. This would affect ocean salinity, and prevent the Gulf Stream reaching as far north.
What are the 4 ecosystem services?
-Provisioning services
-Supporting services
-Cultural services
-Regulating services
What are cultural services?
These are the benefits that people get from visiting or living in a healthy ecosystem. Including:
-Spiritual well-being and happiness
-Recreation and tourism
What are regulating services?
-They link to other physical systems and keep areas, as well as the whole planet, healthy. This includes:
-Purifying water and regulating water flow
-Storing carbon, emitting oxygen and keeping the atmosphere in balance
What are supporting services?
These are services which keep the ecosystem healthy so it can provide other sources. This includes…
-Soil formation
-Food cycling
-Photosynthesis
What are provisioning services?
-These are products which are obtained from ecosystems. They include:
-Fuelwood
-Food e,g nuts
-Timber for building
-Genetic and chemical materials
How do forest fires cause forest loss, and how does this impact human well-being?
Forest fires are one of the main causes of forest loss, especially along dry forest edges. The gas emissions as well as wind-blown dry soil particles result in a lowered air quality both locally and globally.
This causes respiratory problems for humans, such as in Brazil where the 2005 Amazonia drought caused one state to see a 181% increase in hospital emissions.
How does ‘slash and burn’ farming negatively impact human well-being?
Also called ‘shifting cultivation’, and is used by 500million subsistence farmers in the world’s rainforests. While in the past this was sustainable, rising population and poverty levels has caused its sustainability to significantly decrease, as forests don’t get the chance to regrow.
This impacts human well-being due to reduced forest for tourism, a global rise in temperatures due to the deforestation, as well as less fertile soils reducing the crop yield to grow global food supplies.
