Climate change could have had a positive impact on the growth of boreal forest in Canada, but it turns out that drier weather will foil the positive impact of higher temperatures.
These are the claims of a study published in Proceedings of the National Academy of Sciences wherein scientist at Canadian Forest Service have pointed out that though there have been increased green bands in the northern provinces in Canada owing to warmer conditions and increase in carbon dioxide, but drier weather will most likely eliminate the benefits of such favourable weather conditions.
“We find significant regional- and species-related trends in growth, but the positive and negative trends compensate each other to yield no strong overall trend in forest growth when averaged across the Canadian boreal forest”, authors note in the study.
Martin Girardin of the Canadian Forest Service measured growth in boreal forest over the course of last 6 decades in a bid to find how climate change is affecting what is often called one of the largest undisturbed ecosystems left on Earth. Girardin notes that the temperatures at the sties have already increased by between half a degree and three degrees and this could have been the reason why there has been an increase in forest cover.
Forests in British Columbia have expanded and so has the forest cover in boreal stands north of the Great Lakes; however, growth at other places has been less robust. Girardin notes in the study that growth east of the Rocky Mountains has slowed by nearly a percentage point per year. So has growth in the Maritimes and the primary reason seems to be lack of water or in other words dryness.
While temperatures are favourable for growth and so is the increase in CO2 levels, but the lack of water is limiting the growth. Official statistics for summer of 2015 by Agriculture Canada reveal that the Northwest Territories and the northern reaches of the provinces received between 60 and 85 per cent of normal precipitation. Soil moisture was less than 40 per cent of normal.
Dry, warm years can impair growth through increased wildfires and insect infestations. Girardin also suspects nutrient-poor soils are preventing trees from taking advantage of higher carbon dioxide levels in the air. The paper concludes that warmer temperatures have failed to increase growth in the boreal forest.