Wetlands and Forests Regulate Climate via Evapotranspiration

Abstract

The role of wetlands and forests in climate and climate change is usually considered as a part of sequestration system i.e. the source or sink of greenhouse gasses. However, this permanent vegetation is an active factor that, through the process of evapotranspiration directly influences climate. Wet vegetation transforms solar radiation into the latent heat of water vapour. Evapotranspiration is a powerful tool that has, due to phase change of water, a double air-conditioning effect in the landscape. In addition, it reduces thermal gradients, mitigates temperature extremes, close water and mass cycling. Evapotranspiration-condensation processes slow down where there is a lack of water and permanent vegetation. Solar radiation is then transformed into sensible heat. The overheated surface warms the adjacent air layer. Warm air rises turbulently upwards, is capable of absorbing higher amounts of water vapour, which then transmits to higher levels of the atmosphere where condensation occurs. These processes significantly dry out the landscape. The IPCC reports however, do not take into account this direct effect of water and vegetation on climate. The chapter explains the direct function of wetlands and the air-conditioning effect of evapotranspiration, which also illustrates on thermal ground images. Role of forest and wetlands in transport of water from ocean into continents is discussed on literature basis in terms of biotic pump.