According to new study sponsored by the Centre for Ecology and Hydrology, plant respiration is a greater source of carbon emissions than previously assumed, and cautions that as the globe heats, the ability of the Earth's land surface to absorb emissions from fossil fuel combustion may be reduced. The study also concluded that if all terrestrial vegetation were to catch fire at once, it would lead to more atmospheric CO2 than all the world's oil, natural gas, and coal combined. Terrestrial ecosystems are the major source of CO2 to the atmosphere. They do this by decomposing organic matter, which contains carbon, during both their live and dead states. When plants die, they decompose back into the soil ecosystem where bacteria and other organisms continue this process. As these organisms consume the dead plant material, they release oxygen into the air and heat due to the chemical reaction that takes place. Heating water vapor increases the amount of water in the atmosphere, which can have an impact on climate regions far away from where the organism died. When plants grow, they use the energy from the sun's light to produce food using the same processes that animals use. Most photosynthesis happens in the leaves, but some occurs in the stems and roots. Plants use the oxygen that they produce when they photosynthesize to burn other substances, such as methane or carbon dioxide, and use the resulting energy.