Beetles transform Canadian forest from carbon sink into carbon source

In the story of climate change, humans and the carbon dioxide we pump into the atmosphere are the villains of the piece. Now, it seems that we have an accomplice and a most unexpected one at that. It lives in the pine forests of North America and even though it measures just 5 millimetres in length, it is turning these woods from carbon sinks into carbon sources. It's the mountain pine beetle.