Climate change affects greenhouse gas emissions from stream networks
Natural greenhouse gas emissions from streams and lakes are strongly linked to water discharge and temperature according to a new study led by Linköping University, Sweden. This knowledge is necessary to assess how man-made climate change is altering greenhouse emissions from natural landscapes and has large implications for climate change mitigation measures. “The use of agriculture and forestry as carbon sinks is debated at the moment and the question is how effective such carbon sinks are for mitigating climate change. Our new study shows that with increased precipitation, a larger amount of carbon may be washed into streams and lakes and an increased share of this carbon also end up in the atmosphere. Hence, landscape carbon sinks may become less effective in the future,” says David Bastviken, professor at the Department of Thematic Studies Environmental Change at Linköping University. There are large natural carbon sinks because photosynthesis transfer atmospheric carbon first to biomass of plants and algae, and then to soils and sediments where the remains of the biomass are stored. Then there are also large natural climate emissions from the respiration of biomass across the whole landscape. Previously, the natural carbon fluxes were in balance – similar amounts of greenhouse gases were taken up by nature as were released. However, human use of fossil fuels have added a carbon flux to the atmosphere driving climate change. A great concern now is how the changed climate affects the balance of the natural greenhouse gas fluxes. If natural emissions increase faster than natural sinks, we get a vicious circle, i.e. a self-reinforcing effect by which increased emissions affect the climate resulting in greater emissions. This would accelerate climate change even further.