Water and Carbon Cycles- Changes to the Carbon Cycle Flashcards
How do natural wildfires cause a change in the carbon cycle?
- can be started naturally by lightning strikes
- can have regional impacts
- release large amounts of CO2 into the atmosphere- noticeable increase in carbon emissions
How does volcanic activity cause a change in the carbon cycle?
- returns carbon that has been trapped in the lithosphere for millions of years
- at present volcanoes emir 130-180 million tonnes of CO2 each year
- by comparison human activities release 30 billion tonnes
CO2 vs temperature over the past 400,000 years
- as temp. starts to rise at the end of the glacial periods there is a surge in CO2 released into the atmosphere by melting ice
- this surging of CO2 then enhances the greenhouse effect
- positive feedback loop
What is the effect of colder conditions on carbon cycles?
- cold rainwater can hold more CO2 so chemical weathering is more active
- forest coverage would be very different- affects the significance and distribution of processes such as respiration and photosynthesis
- decomposes would be less effective- so carbon transfers to the soil reduced
- more water stored as ice- less transferred to the oceans
- soil is frozen over vast areas- stopped CO2 soil transfer
Affect of warmer conditions on carbon cycles
Melting of permafrost➡️releases previously trapped gases (eg. methane)➡️enhances greenhouse effects➡️positive feedback system leads to further destabilisation of systems
What are the main human causes of changes in the carbon cycle?
- 90% of anthropogenic carbon release comes from the combustion of fossil fuels (primarily coal)
- remaining 10% comes from land use change eg. deforestation
- 50% absorbed by oceans and vegetation and the other 50% by the atmosphere
What is the impact of the combustion of fossil fuels on the carbon cycle?
- natural sources of energy from the remains of living organisms
- long term carbon stores
- when burnt to generate energy, the stored carbon is released (mainly as CO2 into the atmosphere)
What is the impact of changing land use on the carbon cycle?
- responsible for 10% of carbon released globally
- impacts short term stores and has direct links to climate change/global warming
- on a local scale- has a big impact on small scale carbon cycles
What is the impact of farming practices on the carbon cycle?
- machinery used powered by fossil fuels
- use of artificial fertilisers main source of carbon emissions
- soil layers inverted which increases soil microbial activity so more organic matter decomposes
- cattle in the US emit 5.5 million tonnes of methane each year
What is the impact of deforestation on the carbon cycle?
- large amounts of above ground biomass is burnt releasing carbon
- forest clearing accelerates the decay of dead wood
- burning releases CO2 into the atmosphere and if land use changes (eg. cattle ranching) then future CO2 absorbed is reduced
- systems therefore becomes a carbon source not a sink
- without trees, former forest lands can become barren deserts
How does urbanisation affect the carbon cycle?
- replacing open countryside with concrete and tarmac is a major change in land use
- important stores (eg. vegetation) replaces with impermeable surfaces
- urban areas account for 97% of all anthropogenic CO2 emissions
- major sources of emissions are transport and industry
What is geological sequestration
- CO2 captured at its source and injected as a liquid deep underground
- the ocean is able to absorb much more additional carbon than terrestrial systems
- advantage of ocean carbon sequestration is it “sinks” to great depths and reaches the sea bed when it then enters the Earth’s geological system
What is terrestrial/biological sequestration?
- involves the use of plants to capture CO2 from the atmosphere
- the stored in stems of plants and soil
- enriches the plants ecosystem
- land based sequestration plantations are slow growing though and require monitoring
- carbon within such a system is never permanently removed from the atmosphere
