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Trees and climate change: A new review article argues that focus should be on water and cooling rather than carbon

Published on March 12, 2017 | Author: Linus Karlsson
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When trees have been addressed in climate research and climate policies, they have in general been regarded as tools for carbon sequestration. In a new review article, 22 researchers argue that the effect of trees on the hydrological- and the energy cycle is more important.
Trees and forests are essential in the hydrological cycle. Forests play a significant role for the atmospheric moisture distribution by increasing evapotranspiration, the process when water is transformed from liquid to gas. This means that trees increase the local consumption of water but on a regional scale, more moisture will result in more rainfall. Another aspect is the particles, e.g. pollen and spores, which are released into the atmosphere by trees. These small particles are essential when droplets are created and thus when clouds are formed. Trees also increase water infiltration and thereby increase soil moisture and reduce surface runoff, a process that can carry away nutrient rich topsoil.
On a continental scale, forests are important for the inland transportation of moist oceanic air by creating low pressures. They work as biotic pumps and large-scale deforestation could change wind patterns bringing moist air to the continental interiors.
Forests also functions as the air conditioners of the planet. At a local scale, trees shade and cool the soil. At a regional level, evapotranspiration cools the air as this is an energy demanding process. Scientists have confirmed that forests reduce temperatures in temperate and tropical regions with significant effects on extreme heat waves.
All these effects need to be considered when afforestation is promoted through large-scale campaigns or agroforestry. To date the global conversation about climate change and trees has been addressing the effects on the well-studied carbon cycle. Now it is time to change this paradigm and focus on the effects on water and energy. By doing so, the potential of trees and forests as tools for a sustainable development can be fully acknowledged.
Read the full article in Global Environmental Change.

Picture Credit: Ken Kistler, published under the license of CC01.0.