Tundra Disappearing at Rapid Rate due to Climate Change
13.03.2007 - Other
In certain parts of northern Canada, open spruce woodlands are quickly replacing what were once tundra landscapes. As a result, the species living there are being forced out of their ecological niche. According to a new University of Alberta study, this shift can occur much faster than that which scientists originally thought.
The boundary between forest and tundra ecosystems, also called tree-line, was thought to advance very slowly because conditions at these high latitudes and altitudes are so harsh. New data indicates that there has been an upslope surge of trees in response to warmer temperatures. "It's like it waited until conditions were just right and then it decided to get up and run, not just walk", said Dr. Ryan Danby, from the Department of Biological Sciences.
Scientists have reconstructed changes in the density and altitude of tree-line forests in south western Yukon over the past 300 years. Using tree rings, they have been able to date the year of establishment and death of spruce trees and to reconstruct changes in tree-line vegetations.
They found that a rapid change occurred in response to the climate warming during the early mid 20th century and that this phenomenon was observed in all locations. A "positive feedback mechanism" is also at work: as tree-line advances, the reflectance of the land surface declines because coniferous trees absorb more sunlight than the tundra. This light energy is then re-emitted to the atmosphere as heat.
These results are quite relevant to the current debate surrounding climate change because they provide real evidence that vegetation change will be quite considerable in response to future warming. Widespread changes to tree-lines could have significant impacts. As tundra habitats are lost and fragmented, species get forced into smaller and smaller areas.
