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Human impact on the water and carbon cycles - Coggle Diagram
Human impact on the water and carbon cycles
Fossil fuels
Impact of consumption
Massive increase in the amount of carbon stored in the atmospheric store
Carbon locked up in long term geological store is released into the atmosphere, leading to positive feedback loops as carbon in long cycle released
Releases 10 billion tonnes of CO2 annually, with 3/4 of anthropogenic carbon emissions have come from fossil fuels
ocean absorbs far more carbon due to more atmospheric carbon, leading to acidification through carbonic acid which kills coral and phytoplankton who then cannot sequester carbon, leading to a positive feedback loop
Carbon capture/sequestration
Carbon is captured after being burnt, compressed into a dense liquid, and then stored underground in a porous shallow saline aquifer, however uses 20% of energy created
Pre combustion capture involves the separation of fuel using a mixture of water and oxygen
Geosequestration involves pumping the liquid carbon into porous rock with an impermeable rock cap
Involves huge capital costs (Drax and peterhead projects will cost £1 billion
Water extraction
Aquifers and Artesian Basins
Aquifers are permeable/porous water bearing rocks that have groundwater extracted from them for public supply. They provide a significant amount of the base flow of most rivers
Artesian basins occur where sedimentary rocks form a syncline, confining aquifers between impermeable rocks, putting it under artesian pressure. Groundwater tapped here flows to the surface under its own pressure. the level to which it rises (potentiometric surface) is determined by the height of the water table in areas of recharge
Overexploitation of artesian aquifers can lead to water table drops, such as the 90m drop in central London by 1950.
The river Kennet
The Kennet drains an area of around 1200km squared in Wilts and Berks
The upper catchment is the highly permeable chalk which supports extensive biodiversity in the river
Borehole extraction has led to a falling water table that has reduced flow by 10-14%, and springs and seepages to dry up
Global Warming and long term climate change
Water Cycle
Higher levels of evaporation will mean both more water vapour in the atmosphere (feedback loop) and more precipitation worldwide which may increase run off and the risk of flash floods and major flooding events such as the 2021 European floods
When it condenses in the atmosphere, water releases latent heat, providing energy to the atmosphere which will lead to more hurricane and extreme weather events
Water stored in the cryosphere will be reduced, instead moving to the oceans and atmosphere
Risk of destroying the North Atlantic 'conveyor' if Greenland ice sheet melts, massively reducing the temperature in the nearby temperate zones
More precipitation due to more evaporation and convectional rainfall means more water storage on surface, as well as higher runoff and through flow
Carbon Cycle
Higher temperatures will lead to higher rates of decomposition meaning faster transfer of carbon from the pedosphere to the atmosphere
Deforestation will reduce carbon sequestration by biomass, and lead to massive movement of carbon from the biosphere to the pedosphere then atmosphere
Boreal forests may expand however, increasing their NPP and resulting in a negative feedback loop
Permafrost will melt, releasing the methane trapped within it, providing a massive feedback loop, as well as albedo effect. this also allows decomposition of the vast peat stores
Increased sequestration of carbon in the oceans will lead to acidification and the death of phytoplankton and zooxanthellae
Land Use changes
Urbanisation
Urbanisation leads to much higher levels of surface runoff, as most urban surfaces (concrete, steel) are impenetrable for water, so precipitation cannot infiltrate in the way ti otherwise would have. this leads to more rapid water transfer into streams and rivers
Much lower levels of EVT due to lack of vegetation, resulting in lower humidity and precipitation
Risk of flooding significantly increased as floodplains are built on, reducing the ability of the drainage basin to store water after precipitation
Lower carbon storage in biomass, and lower carbon sequestration, as well as increased use of fossil fuels to power the urban area
Farming
Need for crop irrigation means that water is diverted from groundwater and streams/rivers to fields, most of which is lost due to evaporation and soil drainage
Interception is much lower, as crops can intercept far less than forests which contributes to soil erosion and surface runoff which means higher peak flows in nearby waterways
Ploughing increases surface runoff due to the furrows created, but also increases evaporation from the soil
Reduces carbon stored in biomass due to lower biomass of crops, and ploughing reduces soil carbon storage as organic matter is exposed to oxidation
Photosynthesis is lower due to reduced biodiversity, meaning slower carbon exchanges
Forestry
Much higher interception in plantations in natural forest, with Sitka Spruce plantations intercepting 60% of precipitation
More interception means more EVT, and therefore reduced run off and much lower stream discharge
lag times are much longer
However felling of the trees leads to sudden changes within the water cycle
Much higher carbon sequestration and storage in biomass, as much as ten times higher than grassland
Forest soil stores much more carbon due to the ideal conditions for decomposers
Management of the water and carbon cycles
Wetland restoration
Contain 35% of terrestrial carbon
Human activity has had a significant impact on Wetlands, with the lower 48 US states halving their wetland areas since 1600
112,000 ha have been targeted for restoration in Canada, due to the significant amount of carbon they can store
Sustainable agricultural practice
Zero tillage farming reduces runoff and water loss from the system as there is no ploughing. Crop residues can also be left on the ground to prevent soil erosion
Polyculture and agroforestry in the rainforest means growing trees between crops, which increases interception and root uptake, and stores much more carbon
Higher quality animal feed reduces the amount of Methane created by fermenters, reducing emissions
Storage of manure in anaerobic containers
Reducing emissions
Paris accords of 2016 aims to keep temperature rise to below 2 degrees through red icing emissions to 60% of 2010 levels by 2050
Countries also set their own voluntary targets, which are better suited to the individually
However some countries feel it is unfair that their growth should be restricted, while developed countries were allowed to grow without regulation
Cap and trade systems
Forestry techniques
UN's REDD scheme and World bank's FCPF fund more than 50 countries to protect their forests, providing financial incentives that can compete with commercial interests such as logging and agriculture
Amazon Regional protected Areas program now covers more than 10% of the Amazon Basin, offsetting 430 million tonnes of CO2 annually
Afforestation helps to sequester large amounts of carbon, as well as prevent soil erosion and flooding
Importance of selective and sustainable logging
Water allocations
Agriculture accounts for about 70% of global water withdrawals and 90% of consumption, much of which is wasted due to drainage or inefficient water management systems. Drip irrigation reduces these losses, as can contour planning
Regions of water scarcity like the Colorado basin, agreements must be made to divide up water with downstream states or countries
Drainage basin planning
Planning basin by basin is the most efficient way to plan
UK has 10 basin districts
planning aims to control surface runoff, channel flow and through flow
Reforestation can be used to affect runoff in rural areas, while artificial drainage sytstems can be used in urban areas
For example in Las Vegas homes have used xeriscaping to reduce water usage by gardens
Building in dams or reservoirs where there is excessive runoff prevents flooding
Monitoring of the water and carbon cycles
Ways of monitoring the cycles
Arctic sea ice
Measured using NASA's EOS satellites using measurements of microwave energy from Earth's surface
Sea Surface Temperatures
Measured with NOAA satellites with radiometers to see zones of up and downwelling
Atmospheric CO2
NASA's Orbiting Carbon Observatory and ground based measurements to measure CO2 in atmosphere and effectiveness of sequestration by plants
Why is it important to monitor the cycles?
Climate change means that changes to the water and carbon cycles are more important now than ever before. Importance of the cycles means changes need to be recorded. Data such as ice core data shows PPM is now 480, despite fluctuating between 180 and 280 before industrial revolution
Climate change can lead to deforestation, desertification, catastrophic flooding, higher temperatures and cyclones. Therefore we need to measure it to plan a response