Invading Trees Likely to Cause Increased Warming in the Arctic
13.01.2010 - Atmosphere & Space, Land & Geology, Flora & Fauna
Trees seem to be slowly moving northward as the tundra in the Arctic melts. According to a study from University of California Berkley scientists published in the online Early Edition of the journal Proceedings of the National Academy of Sciences, the northward expansion of the treeline (the northernmost point at which trees can grow) in the Arctic will have a widespread influence on warming in the Arctic. The study shows that, besides absorbing more light than bare tundra because they are darker, broad-leaved trees also release a lot of water vapour, a greenhouse gas that causes more widespread warming.
Because they are less dark than evergreens, broad-leaved trees are generally considered to be less important regarding Arctic warming, but the researchers discovered that the water vapor they release increases the greenhouse effect.
The increased water vapour would melt more sea ice, resulting in more absorption of sunlight by the open ocean and dumping more water vapour into the atmosphere. This in turn will further warm the land and encourage faster, more efficient tree growth resulting in a faster expansion of trees into the Arctic – essentially creating a positive feedback situation. While this increase in temperatures will likely to cause an additional 1°C over the Arctic, global warming might increase temperatures in the Arctic between 5°C and 7°C within the next 100 years.
Although previous studies on vegetation impacts on global warming were mostly focused on the albedo of vegetation, this new study proves water transpiration to have a significant impact as well, especially in environments like the Arctic.
While scientists are now trying to identify the physical processes these changes will entail, the Arctic is already becoming shrubbier, which could likely make the climate more welcoming for other trees species.
