Arctic treeline advancing slower than previously thought
It has long been believed that 40 per cent of Arctic tundra would disappear by the end of the century. New research tells a different story.
The Arctic treeline is moving northward, but not as rapidly as previously believed, researchers say.
Previous estimates suggested the Arctic treeline was advancing northward at a rate of two kilometres a year, as a result of a warmer climate. If these estimates were accurate, they would mean a 40 per cent loss of tundra by the end of the century.
This is a huge overestimate, Annika Hofgaard, coordinator of the PPS Arctic project on circumpolar treeline research, told the Barents Observer. Ecologists have long suspected the estimate did not fit reality, Hofgaard says. It was an estimate that was assumed to be true over time as it was repeated by media and policymakers.
Instead, the PPS Arctic research suggests the treeline is advancing by an average of 100 metres a year in Finnmark. This would mean only two per cent of tundra would disappear by the end of the century.
The international research is based on sattelite images and hand-drawn maps from the past 100 years, as well as on-site research across the Arctic.
The previous estimate, Hofgaard says, did not take into account many factors. In some areas, fewer animals grazing the land has led to forest cover that is denser, though not necessarily moving northward. In other areas, forest that is recovering from disease may appear to be rapidly increasing.
Some sites studied by the researchers in Finnmark and Siberia have even experienced a decline in forest growth.
In areas where reindeer herding is still common, grazing pressure has maintained the treeline. Reindeer tear the leaves off of trees preventing small trees from growing.
“Reindeer are cultural engineers,” Hofgaard says. “They are keeping the Sami landscape the way it used to be.”
“All of these factors make it more or less impossible for the forest to advance two kilometres a year.”