August 13, 2009

Climate warming and treelines studied

New Zealand scientists say a study of climate change suggests global warming is not spurring the advancement of Earth's treelines as expected.

Scientists at New Zealand's Bio-Protection Research Center said their study -- the first global quantitative assessment of the relationship between climate warming and treeline advancement -- tested the premise that treelines have been advancing since 1900 in response to global warming.

Treelines are the elevation at which trees are capable of growth or survival and are considered to be early indicators of climate warming because they are constrained primarily by low temperatures.

Harsch and her colleagues used a multivariate meta-analysis of a global dataset of 166 treeline sites with temperature data taken from the closest climate station to each site. The team used the data to analyze treeline advance through the 20th century.

They found only 87 of the 166 sites, or 52 percent, had advanced, although the mean annual local temperatures had increased at 111 of the 166 sites. Of the remaining sites, 77, or 47 percent, were stable and only two sites had treelines that receded.

The findings are detailed in the journal Ecology Letters.