Scientists say climate change is forcing the boreal forest that covers much of northern Canada to a tipping point.
The study, published today in the journal Science, points out that temperatures are expected to rise faster and higher in the boreal forest than anywhere on Earth.
Those temperatures are likely to bring drier conditions, new diseases, insects and huge wildfires to the vast green belt that covers much of the planet's northern latitudes.
Researchers say the forests can't spread north fast enough to escape the new conditions.
The old forests are unlikely to grow back once they've been damaged, leaving a new landscape with much more open space than the former unbroken expanse of green.