6.7 Flashcards
Why is terrestrial biosphere important
sequesters about a quarter of fossil fuel CO2 emissions annually, directly slowing down global warming.
What is Land Conversion
Any change from natural ecosystems to an alternative use;it usually reduces carbon and water stores and soil health.
Main drivers of global deforestation
- Increasing demand for commodity production. Half of all current deforestation is for soy, palm oil, beef and paper production.
- Other causes of land conversion are; dams and reservoirs, infrastructure and open cast mining.
By 2015, 30% of all global forest cover had been completely cleared, 20% degreased and rest fragmented.
Where is levels of deforestation highest and main driver
Madagascar
Growing international demand for tropical hardwood, expanding population and debt repayments.
What has Madagascar government being encouraging farmers to do
Clear more land to grow cash crops to earn foreign currency. Will help repay country’s debt. Since 1950s, Madagascar’s tropical forests have been cleared at a rapid rate. Small-scale clearance by farmers had long been common in country.
Effect of deforestation in Madagascar
Before 1950, Madagascar had 11.6 million hectares of tropical forest, but by 1985 reduced to 3.8 million hectares (loss two-thirds)
Trends in deforestation in temperate forests
such as UK and USA, have long history of exploitation. 90% was deforested by 19th century.
Trends in deforestation in boreal forests
been increasingly threatened since mid-20th century. E.g by oil and tar sands production in Russia and Canada.
Trends in deforestation in tropical forests
Lost half their area since 1960s, especially in Africa and S. America. However, remote sensing shows Indonesia has recently overtaken Brazil in rate of deforestation. Mainly for palm oil production and logging.
Deforestation implications to carbon cycle
Deforestation and major impact on size of terrestrial carbon store.
Removing forest has huge impact on both fluxes and stores.
Deforestation implications to water cycle
- Infiltration decrease
- Runoff and erosion increase
- Annual rainfall decrease
Deforestation implications to soil health
- CO2 is released from decaying woody material
- Rapid soil erosion leads to a loss of nutrients
- Raindrop impact washes finer particles of clay and humus away
What is Afforestation
Planting trees on land that has never had forest, or has been without forest for a long time.
What is Reforestation
Planting trees in places with recent tree cover, replacing lost primary forests.
Why a net gain of forested area been observed in parts of NA and Asia
2014, New York Declaration of Forests set global target to restore 350 million hectares of deforested and degraded forest landscapes by 2030.
China’s Three-North Shelterbelt Project is 4500km green wall of trees designed to reduce desertification
Controversy of afforestation/reforestation
controversial in its impacts on landscape character as well as on carbon, water and soil systems.
Monoculture of commercial trees, such as in palm oil plantations and non-indigenous species, often store less carbon, use more water and disease prone.
Where is grasslands being converted to farming
2007-2015, biofuel ‘rush’ swept across American Midwest - often referred ‘Prairies’. Farmers encouraged to grown corn, soya, canola and sugar cane as part of US Environmental Protection Agency’s Renewable Fuel Standard policy
US Environmental Protection Agency’s Renewable Fuel Standard policy aims
Policy aimed:
- Increase amount of ethanol used in petrol
- Boost economies of rural US states
- Reduce US dependence overseas oil imports
- Reduce CO2 emissions from transport
Main impacts of converting grasslands
Serious consequences for carbon and water cycles, as well as for soil health.
America’s Midwest is prone to dry summers, and at risk from wind-blown soil erosion, which would also have a detrimental effect on the soil carbon store.
Benefits of grassland converting
act as a carbon sink — absorbing CO2 and releasing 02 all year round (a ‘lung effect’)
absorb toxins from soils. maintain healthy soils
maintain natural habitats
Disadvantage of of grassland converting
Initial removal of grasslands releases CO2 from soils into atmosphere
Cultivated soils are liable to erosion by runoff and wind
