Changes in biome carbon storage due to human activity (Afforestation (What…
Changes in biome carbon storage due to human activity
Rainforest timber harvesting has been occurring for centuries to meet demands for hardwood furniture and flooring, despite attempts by countries such as the UK to restrict imports.
Huge areas of the Amazon have been cleared for agricultural use, averaging 17'5000 square kilometres per year between 1975 and 2013. Soya beans and cattle farming are culprits in Brazil and Costa Rica, and oil palm cultivation is huge in Indonesia.
What does it do?
Deforestation reduces the carbon biomass store as trees hold far more carbon than croplands, e.g. Soya holds 2.7 tonnes/ha and virgin rainforest 180 tonnes ha.
Increased overland flow can result in soil erosion and the permanent loss of carbon storage capacity
The size of above ground biomass in surviving rainforest is believed to have slightly increased in recent years, which may be due to the sequestering of carbon in the atmosphere, and is therefore an example of negative feedback.
Involves planting trees in areas that have been deforested or have never been forested.
What does it do?
New trees act as carbon stores and aid in climate change mitigation as well as preventing flooding
The UN's Reducing Emissions from Deforestation and forest Degradation scheme provides incentives for developing countries to maintain their rainforests by placing a monetary value on conservation.
The UK Forestry commission as founded in 1919 and initially intended to increase timber supplies following WW1, growing Coniferous trees on marginal land, and now focuses on increasing carbon sequestration.
Monocultures such as commercial connifer plantations increase carbon storage if the replace grassland. They still store less than natural forests due to a lack of biodiversity and habitats.
Carbon offsetting is an individual approach to mitigation which is widely used. It marries business principles with environmental goals, and you compensate for your emissions by funding an equal carbon dioxide saving elsewhere
Historically, excessive cultivation using inappropriate methods has led to soil becoming over-worked, leading to a loss of SOC, and causing land to erode and degrade
Soil erosion occurred hugely in the USA in the 1920s and 1930s because of this, known as the "Dust Bowl" episode. In the Great Plains 65 million hectares of over-cultivated land was stripped of top soil leading to enormous loss of soil carbon capacity.
What does it do?
Affects both biomass carbon storage of land and amount of soil organic carbon (SOC) that is present. SOC is the carbon associated with soil organic matter (made up of humus i.e. decomposed plant and animal materials).
Globally, clearing natural vegetation for agriculture bring a large reduction in SOC. Further declines may occur because of poor management practices. In many farmed areas, SOC levels have fallen to 50% compared with pre-agricultural periods.
Positive changes in carbon storage can also result from agricultural activity, including addition of manure, plant debris, compost and bio-solids from sewage to agricultural soils. These are all high in organic carbon.
Good farming practices include: irrigation, crop rotation, fertiliser management, grazing management, earthworm introduction, improved grass species, introduction of legumes, animal manure, and recycled plant remains.