Scientists have long considered forests in North America as a potential source of mitigation for the effects of global warming, but according to a new study featured in the journal Ecology Letters, it may not offer much of a relief for climate change as initially expected.
Researchers from the University of Arizona (UA) and other scientific organizations examined the impact of trees in North America to find out how they can help reduce the warming effects of climate change on the planet.
While forests have been shown to take up as much as 25 to 30 percent of the total greenhouse gas emissions from human activities, the new study reveals that they may not produce the same level of mitigation as earlier research suggested, based on climate model projections, tree-ring records collected across the continent and the impact of high carbon dioxide (CO2) concentrations on trees.
Impact Of Climate Change On Tree Growth
The UA-led study is the first of its kind to look at the potential effects of global warming on the growth rate of trees in North America. The researchers were able to create forecast maps that detail how the changing climate will affect the development of forests in the continent.
The team made use of climate projections for the region provided by the International Panel for Climate Change (IPCC) and combined them with historic tree-ring data collected from 1,457 sampling sites from 1900 to 1950.
Noah Charney, lead author of the study from UA's Ecology and Evolutionary Biology Department, said that after they gathered their data, they examined the growth of trees that experienced significant changes brought on by previous climate shifts. They then used their observations to determine how trees in North America will continue to develop in the future.
Study co-author Brian Enquist said that their work is unprecedented and novel when it comes to the use of large-scale biological data. As many as 2 million observations on tree-rings were collected from across North America as part of their study.
"Tree-rings provide a record into how trees that grow in different climates respond to changes in temperature and rainfall," Enquist said.
The new findings contradict earlier conclusions regarding the response of forests to various factors such as changing rainfall patterns, warmer average temperatures and an increased level of carbon dioxide emissions.
Charney and his colleagues weren't able to find any evidence of boreal greening effect, a process in which forests are expected to absorb greenhouse gas emission in the atmosphere.
Some scientists believed that trees located in colder temperatures would benefit from the increased carbon dioxide levels and warmer temperatures brought on by climate change. This in turn would allow boreal forests to absorb the abundant CO2 in the atmosphere, reducing the impact of climate change on the planet.
The researchers pointed out that many climate model studies conducted in the past depended on boreal forests to offset the effects of global warming, but they weren't able to see any greening in their own analysis. They instead found the opposite effect, which is a browning of forests.
The new study shows that forests located in the interior West of North America are the ones that will most likely experience significant changes in their development. The growth rates of trees along the Rockies, Alaska, southwestern United States and Canada are likely to slow down by as much as 75 percent.
On the other hand, trees located along certain coastal regions such as Northeastern Quebec, the Florida panhandle and the Pacific Northwest are expected to experience an increase in growth rate in the coming years.
Despite using only data from within the North American continent, the researchers believe their observations could also be applied to other parts of the world, especially to boreal forests found in Eurasia which are considered to be more extensive and important than those found in North America.
Photo: Susan Drury | Flickr
