Soil influences on climate

You should know carbon is released by power stations, aeroplanes and car exhausts? But did you know that soil also contains some of the most important greenhouse gases? Soil contains huge stores of carbon, which breaks down more readily at higher temperatures. The carbon content of a soil can vary from about 1 percent in sandy soils to 40 percent in peat soils. What is happening to this soil carbon as the climate changes is a big concern. Soil mainly enters soil in the form of plant material, and leaves soil mainly as CO₂ due to respiration during the microbiological decomposition of soil organic matter. The natural balance of this is part of the 'carbon cycle'.

Shifts in the balance of this cycle can be caused by changes in land and soil management or by changes in the climate. This can mean either more carbon leaves than enters soil from the atmosphere, or the opposite. Because of this, we need to manage land carefully to try to reduce CO₂ being released from soil. There are a number of ways to look after the land which can help achieve this - one example is not letting wetlands dry out. There are other important 'greenhouse gases' which can be released by the soil, for instance methane and nitrous oxide. In fact half of all the methane and nitrous oxide reaching the atmosphere comes from soils. You might know that waterlogged soils such as paddy fields, flooded for growing rice, release a lot of methane. You probably didn't know that the digestive systems of termites do too - and there are a LOT of termites in the tropics and subtropics! In colder temperate regions, the wet soils in marshes and bogs are significant sources of methane. Lots of methane is also given off from landfill sites (rubbish dumps). Did you also know that cows constantly let off methane (they fart a lot!)

As well as methane, about half the global nitrous oxide (N₂O) emissions come from agricultural soils, or natural and semi-natural landscapes. Much of the recent increase in N₂O in the atmospheric is due to the global increase in use of nitrogen fertilisers to improve the soil.