PLEA Network

6 March 2016, Climate News Network, Risk level rises for North American forests. The speed at which the climate is changing is outstripping forests’ ability to adapt to drier, hotter conditions across vast swathes of the US and Canada. Drought and climate change are now threatening almost all the forests of the continental US, according to new research. Scientists from 14 laboratories and institutions warn in the journal Global Change Biology that climate is changing faster than tree populations can adapt. Existing forests, effectively and literally rooted to the spot, are experiencing conditions hotter and less reliably rainy than those in which they had evolved. “Over the last two decades, warming temperatures and variable precipitation have increased the severity of forest droughts across much of the continental United States,” says James Clark, professor of global environmental change at Duke University, North Carolina. He and colleagues synthesised hundreds of studies to arrive at a snapshot of changing conditions and a prediction of troubles ahead. Ominous predictions Other research has already delivered ominous predictions for the forests of the US southwest, but the scientists warn that other, normally leafier parts of the continent face increasing stress. Dieback, bark beetle infestation and wildfire risk may no longer be confined to the western uplands. “While eastern forests have not experienced the types of changes seen in western forests in recent decades, they too are vulnerable to drought and could experience significant changes with increased severity, frequency, or duration in drought,” the authors say. Professor Clark puts it more bluntly: “Our analysis shows virtually all US forests are now experiencing change and are vulnerable to future declines. Given the uncertainty in our understanding of how forest species and stands adapt to rapid change, it’s going to be difficult to anticipate the type of forests that will be here in 20 to 40 years.” Read More here