Trees Losing to Climate Change, Less Likely to Protect Us From Its Adverse Effects

A new study revealed that trees in North American forest will not be of much help in mitigating the effects of higher concentration of carbon dioxide in the atmosphere.

Previously, scientists assumed that trees in high latitudes benefit from the warmer temperature and higher concentrations of carbon dioxide in the air due to the growth limitations imposed by the colder temperatures in the region. This assumption is known as the boreal greening effect and is believe to dampen climate change by greening under its effects.

However, a study published in the Ecology Letters found no evidence supporting the boreal greening effect in their simulations, Furthermore, the study also suggests that trees in higher temperatures actually benefit in warmer climate, but once they reach the tipping point, the increasing temperature may be more detrimental than beneficial in tree growth.

"Many previous climate modeling studies counted on the boreal forests to save us from the climatic disaster by offsetting our emissions, but we don't' see any greening in our results," explained Valerie Trouet, an associate professor in the UA's Laboratory of Tree-Ring Research (LTRR), in a statement. "Instead, we see browning. The positive influence warmer temperatures are believed to have on boreal forests -- we don't see that at all."

For the study, the researchers analyzed the combined climate projections for North America developed by the International Panel for Climate Change (IPCC) with historic tree-ring records based on samples covering the period 1900 to 1950 at 1,457 sampling sites across the continent.

Using the data on how the growth of trees changed historically under various past climate, the researchers then predicted how the trees will grow in the future across the continent from Mexico to Alaska.

Their projection showed that trees in the Southwestern United States will have up to 75 percent decrease in their growth rate. Furthermore, the researchers discovered that the warming climate might already been pushing many forest towards their tipping point, which may be reached as early as 2050.

Due to the slowing growth rate of trees, forest may soon turn from being climate asset to a carbon producer very quickly.

Researchers noted that their study is only involving boreal forest in North America. However, researchers believe that the conclusion drawn from their study can also be applied in other boreal forest outside the continent, especially boreal forest in Eurasia, which is known as more extensive and as more important than the boreal forest in the North America.