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Even moderate warming will transform northern forests

Boreal forests in the far north make up the largest forested region in the world. These ecosystems are extremely important for capturing carbon. Unfortunately, research shows that climate change is already impacting northern forests in both positive and negative ways. 

Boreal forests are composed mainly of conifer species such as spruce, fir, and pine. There are also a few much less common broadleaf hardwood trees such as oak and maple. Experts have determined that global warming is likely causing a decrease in growth in the conifers, along with an increase in growth in the hardwoods. 

These observational studies were recently confirmed and enhanced by a rare experimental study on the impact of climate change on northern forests.

Nine species of native boreal trees were planted and grown under different conditions. Some of the trees were left alone as controls. Others were grown with temperatures raised by two hypothetical amounts: 1.6 degrees Celsius (2.9 degrees Fahrenheit) and 3.1 C (5.6 F) above natural temperatures. Some of the trees were covered by tarps prior to storms to mimic a reduction in rainfall.  

The results of the analysis showed that even a moderate change in climate is likely to have negative impacts on boreal forest composition. 

Study lead author Paul Reich is the director of the Institute for Global Change Biology at the University of Michigan’s School for Environment and Sustainability and a forest ecologist at the University of Minnesota.

“Our results spell problems for the health and diversity of future regional forests,” said Reich. “Present-day southern boreal forest may reach a tipping point with even modest climate warming, resulting in a major compositional shift with potential adverse impacts on the health and diversity of regional forests.”

“Those impacts could reduce the capacity of our forests to produce timber, to host other plant, microbial and animal diversity, to dampen flooding, and – perhaps most important of all – to scrub carbon out of the air and hold it in wood and soil.” 

The researchers found that elevated temperatures increased the death rate of all nine of the tree species and the growth rate of seven of the trees. This suggests that there will be a shift in boreal forests in the future and the potential incursion of invasive species already in temperate forests. 

The study is published in the journal Nature.  

By Erin Moody , Staff Writer

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