p8 Flashcards
Afforestation =
planting trees on land that has never had forest, or has been without forest for a long time.
Reforestation =
planting trees in places with recent tree cover, replacing lost primary forests.
problems with Afforestation
Afforestation tends to be made up of monocultures (1 single crop/species) such as palm oil. They often store less carbon, use more water and are disease prone.
Afforestation e.g
For example: China’s Three-North Shelterbelt Project – a 4,500km green wall of trees designed to reduce desertification – demonstrates many of these issues.
Impacts of Afforestation on carbon cycle:
Monocultures of commercial trees such as in palm oil plantations often store less carbon although it’s better than having no vegetation at all.
Biodiversity may be impacted as a result of habitat changes.
Monocultures tend to be more disease prone having a negative impact on biodiversity.
Impacts of Afforestation 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.
two main types of grassland – what are they?
Temperate Grasslands
Tropical/Savannah Grasslands
Both the carbon and water cycles are disrupted when they are used too intensely for animals or when ploughed up.
Grassland Conversion - USA
For example, between 2007 and 2015, a biofuel ‘rush’ swept across the American Midwest – often referred to as the Prairies.
During this ‘rush’ farmers were encouraged to grow corn, soya, canola (a type of rapeseed) and sugar cane as part of the US Environmental Protection Agency’s Renewable Fuel Standard Policy which aimed 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
By 2013 the price of corn trebled, and a number of US states were cashing in.
Grasslands – traditionally used for cattle ranching - were ploughed up, and in some states the area of corn being cultivated doubled.
Over 5.5 million hectares of natural grassland disappeared across the American Midwest, which matches the rate of rainforest deforestation across Brazil, Malaysia and Indonesia
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 conversion
Soils release CO2 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 CO2 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 lost
Causes of greenhouse effect
agriculture, industry, transport, deforestation, electricity generation, cement production, wetland/peatland loss.
Consequences of greenhouse effect
increase in frequency and intensity of storms and tropical storms; rising temperatures; rising sea levels; more frequent floods, droughts and heat waves.
What is drought?
An extended period of deficient rainfall relative to the statistical average of that region measured over a long period of time.
How does climate change cause drought?
Shifting of global weather patterns
Shifting climate zones
Scientists at the University of Colorado have found that a warming of 2 degrees resulted in about 5% of the Earths land area effectively shifting into a new climate zone.
The pace of change then increases for the next 2 degrees of warming with an additional 10% of land area shifting to a new climate zone.
Risk of Drought
An expansion of subtropical deserts and a poleward movement of stormy, wet weather in the mid-latitudes – there is already evidence of this.
Changing snow/rainfall patterns and increasing temperatures in mountain regions could cause reliable streams/springs dry as well as melt glaciers resulting in a very little run off in the future.
