WESTERN CANADIAN BOREAL NO LONGER A SINK?

According to an article on the science site Physorg.com, the boreal forests of Western Canada may no longer be acting as carbon sinks. Based on a report by researchers from Quebec and China, the article suggests long-term drought conditions may be the cause.

If the situation remains as it is, the forests may actually put more carbon dioxide back into the air than they absorb, the researchers said. While researchers have seen this happen in tropial rainforests, the new result suggests that this problem could be much more widespread.

The scientists at the University of Quebec’s Montreal campus and from several Chinese institutions, reporting in this week’s Proceedings of the National Academy of Sciences, have been able to put numbers to the fears that the ability of northern forests to absorb carbon -- to act as carbon sinks -- was decreasing.

The researchers studied 96 permanent old-growth forests out of 20,000 candidates, concentrating on aspens, which are more sensitive to changes in precipitation.

They deliberately chose forests that were not affected by insect infestation or fires. They then estimated biomass production -- the growth of the trees -- from 1968 to 2008.

Trees in both east and west were dying sooner, but the eastern forests were replacing biomass while the forests in the western provinces of Manitoba, Alberta and Saskatchewan were not. The west has had less precipitation and rising temperatures, which they believe is the cause.

"Our results indicate that since 1963, drought-induced water stress has led to a weakening of the biomass carbon sink across a large area of the western Canadian boreal [northern] forests, with the largest reduction after 2000," they wrote.