Enquiry Question 3: How are the water and carbon cycle linked to the global system? Flashcards
Annual change in forest area, 1990-2015
- South America has seen a lot of deforestation, specifically Brazil, which has a net loss of >500
- Africa has a net loss of 250-50
- Indonesia has a net loss of 500-250
- An area which hasn’t seen much loss (50-250 net gain) is Russia
- Europe has seen a lot of net gain, however a majority of it is small
- India and America have the highest net gains at 250-500
Tropical forests have lost ___ of their area since the 1960s
50%
What percentage of temperate forests had been deforested by the 19th century?
90%
What fraction of carbon dioxide does the terrestrial biosphere sequester/store annually?
1/4
How can land conversion affect the carbon and water stores?
Land conversion could change the land from a natural ecosystem to an alternative use, which usually reduces carbon and water stores as well as soil health
Deforestation - impacts on the water cycle
- Infiltration is decreased
- Flood peaks are higher and the lag time is shorter
- Increased discharge leads to flooding
- More eroded material is carried in the river, bot has bed load and as silt and clay in suspension
- Annual rainfall is reduced and the seasonality of rainfall increases
Deforestation - impacts on soil health
- Raindrop impact washes finer particles of clay and humus away
- Coarser and heavier sands are left behind
- Carbon dioxide 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 (the loss of nutrients from the soil by infiltration) means that minerals are lost
Deforestation - impacts 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
- The air is dryer
- Evapotranspiration rates from the resultant grasslands are about one-third that of the tropical rainforests
Deforestation - impacts on the biosphere
- Evapotranspiration from vegetation is reduced
- Less absorption of carbon dioxide means a reduced carbon store
- Species diversity is reduced (e.g. less-resilient forest plants die off)
- Ecosystem services are reduced
- The decrease in habitats means that fewer animal species survive
- Biomass is lost , because of reduced plant growth/photosynthesis
Causes of deforestation (why people do it)
- 50% of all deforestation is for soy, palm oil, beef and paper production
- Dams and reservoirs
- Infrastructure
- Open cast mining for rare materials
Methods of deforestation
- Clear cutting - used for loggings, removes all primary forest
- Slash-and-burn - used for agriculture - trees are cut and set alight. Ash from the trees provides nutrients for the soil
What percentage of forests in Madagascar has been deforested?
90%
Who is to blame for the deforestation happening in Madagascar?
Private industrial companies
What do the local people in Madagascar use the forest for?
- Agriculture (mango growing)
- Medicines
- Charcoal (cooking, domestic heating)
- Infrastructure (village housing) - due to increased populations
Why are the forests in Madagascar so vulnerable?
- Increasing population
- Lack of government support
- No international aid
- Growing international demand for tropical hardwood
What are the solutions to the deforestation in Madagascar?
External workers to work locally to provide an alternative solution for the local population
What are the negative impacts if the rate of deforestation continues?
- No remaining forest
- Long term droughts and extending monsoon seasons
Afforestation
- Planting trees on land that hasn’t had forest, or has been without forest, for a long time
Reforestation
Planting trees in places with recent tree cover, replacing lost primary forests
Afforestation - impacts on carbon cycle
- Monocultures of commercial trees such as in palm oil plantations often store less carbon
- Biodiversity may be impacted as a result of habitat changes
- Monocultures tend to be more disease prone - has a negative effect on biodiversity
Afforestation - impacts on water cycle
- Monocultures tend to use more water leading to less infiltration and groundwater rates
- Decreased raindrop erosion
- Evapotranspiration rates may alter surrounding downwind ecosystems
Monoculture
The agricultural practice of producing or growing a single crop, plant, or livestock species, variety, or breed in a field or farming system at a time
Example of afforestation
China’s Three-North Shelterbelt project - a 4500km green wall of trees designed to reduce desertification
Grassland conversion in the USA
- 2007-2015 = biofuel ‘rush’ swept across the Prairies
- During this, farmers were encouraged to grow corn, soya, canola, and sugar cane as part of the US Environmental Protection Agency’s Renewable Fuel Standard Policy
- By 2013, the price of corn trebled
- Over 5.5 million hectares of natural grassland disappeared across the Prairies (matches the deforestation rates across Brazil, Malaysia and Indonesia)
US Environmental Protection Agency’s Renewable Fuel Standard Policy aims
- Increase the amount of ethanol being used in petrol
- Boost the economies of rural US states
- Reduce US dependence on overseas oil transport
- Reduce carbon dioxide emissions from transport
Benefits of natural grasslands
- Trap moisture and floodwater
- Absorb toxins from the soil, maintaining their health
- Providing cover for dry soils - preventing soil erosion
- Maintain natural habitats
- Acts as a carbon sink and a terrestrial carbon store
Drawbacks of grassland conversion
- Soils release carbon dioxide when grasslands are initially removed and through annual ploughing
- Biofuel crops need carbon-based nitrogen fertiliser and chemical pesticides, so they produce a net increase in carbon dioxide emissions
- Biofuels consume a lot of water, impacting on local aquifers for irrigation
- Cultivated soils are liable to erosion by surface runoff and wind
- Natural habitats are lost
Drought
An extended period of deficient rainfall relative to the statistical average of that region measured over a long period of time
Palm oil
- The most commonly produced vegetable oil
- 68 million tonnes are produced each year
- Tropical climate is perfect for maximising crop yields
- A huge driver for deforestation
How many land conflicts had been linked to palm oil in 2016?
700 - indigenous people driven out of areas they had inhabited for generations
How many people depend on forests? What percentage of these are the poorest in societies?
1.6 million people, 90%
Forests are the source of what percentage of global biodiversity?
80%
Forests provide what percentage of the global economy income?
1.1%