Even modest climate change imperils northern forests: Study

PARIS: Even relatively moderate heating and rainfall loss could dramatically alter the make-up of Earth’s northern forests, risking their biodiversity rich ecosystems and undermining their ability to store planet-warming carbon pollution, researchers said Wednesday (Aug 10).

Boreal forests cover much of Russia, Alaska and Canada and are a major carbon sink, but they are menaced by more frequent wildfires and invasive species outbreaks linked to climate change.

To assess how higher temperatures and less rainfall may impact the tree species most commonly found in the forests, a team of researchers based in the United States and Australia conducted a unique five-year experiment.

Between 2012-2016 they grew about 4,600 saplings of nine tree species – including spruce, fir and pine – in forest sites in northeastern Minnesota.

Using undersoil cables and infrared lamps, the saplings were warmed around the clock at two different temperatures – one lot at 1.6 degrees Celsius hotter than ambient, the second at 3.1 degrees Celsius warmer.

In additional, moveable tarps were positioned over half the plots before storms to capture rainwater and mimic the type of precipitation shifts that climate change is anticipated to bring.

The study, published in Nature, found that even the trees grown under 1.6 degrees Celsius of warming experienced major problems, including reduced growth and increased mortality.

“I thought we’d see modest declines – of a few per cent – in survival and growth for even the boreal species like spruce and fir, but we saw very large increases in mortality and decreases in growth in a number of species,” lead author Peter Reich told AFP.

The team found that warming on its own, or combined with reduced rainfall, increased juvenile mortality in all nine tree species studied.