The peatlands of North West Europe and Climate Change

Abstract

Peatlands are one of the world’s most important ecosystems. Covering a mere 3% of the world’s terrestrial surface, peatlands contain 550 Gigatonnes (Gt) of carbon making them the most important long term carbon sink in the terrestrial biosphere. This ability of peatlands to store CO2 and GHG means they have a net cooling effect on the global climate. It has been estimated that in the last 10,000 years since the last Ice Age the atmospheric carbon sequestered in peats has served to reduce global temperatures by about 1.5–2 °C. Humans have been causing the degradation of peatlands in NW Europe for centuries through management regimes such as the draining of peatland for forestry and agriculture. More recently humans have been causing the degradation of peatlands indirectly through anthropogenic climate change. The degradation of pristine peatlands causes the release of considerable amounts of CO2, DOC, POC, sediment and N2O causing peatlands to switch from net GHG sinks to sources. The degradation and destruction of peatlands causes the release of 3 Gt of CO2 annually. Climate change is already affecting peatland ecosystems and its influence will only get stronger in the future. The response to changes in temperature, precipitation, hydrology and vegetation will vary greatly between ecosystems and regions. Some ecosystems such as palsa will be extremely vulnerable to a changing climate. The melting of permafrost will lead to the release of vast amounts of CH4 and CO2 that will provide a positive feedback to global warming. Some peatland ecosystems may benefit from a longer growing season with increased primary production. This may have a positive effect on C sequestration although a warmer climate with more regular droughts will cause the lowering of peatland water table and the invasion of vascular plants and trees onto the peat surface which will cause the loss of the peat C stocks. Over the short term these changes will likely see the release of vast amount of GHG that will create a positive feedback to climate change (Betts et al., 2004; Friedlingstein et al., 2010; Lewis, 2006). Peatlands however have adapted to climate change in the past and warmer temperatures will open up new territories for peatlands to colonise. It is unclear how the peatland ecosystems will respond to climate change in the future. What is clear is that the management of peatlands by humans will greatly influence the extent of peatland loss caused by climate change. In turn management decisions will affect the rate of mineralisation and the loss of the C sequestration capacity of peatlands this will affect the rate of future climate change. The rewetting and restoration of peatlands has the capacity to secure existing carbon stocks and reinitiate the C sequestration capacity of degraded peatlands. Peatland restoration projects have been recognised by the new Kyoto Protocol and should be incorporated into the very heart of the national greenhouse gas reduction strategy of Ireland, Britain, Finland, Norway and Sweden.