An army of rice-grain-sized beetles, attracted by warming weather, has moved into Canada's western forests, where its tree massacre is causing the mercury to rise yet further, a study said Sunday. The voracious horde of mountain pine beetles has invaded about 170,000 square kilometres (65,000 square miles) -- a fifth of the forest area of British Columbia, Canada's western-most province, a research team wrote in the journal Nature Geoscience. The beetles lay their eggs under the bark of pine trees, at the same time injecting a fungus that protects their offspring but kills the trees with the help of the larvae eating their insides. As trees are felled, the cooling effect of their transpiration, similar to human sweating, is also lost. The researchers measured a corresponding rise in summertime temperatures -- about one degree Celsius (1.8 degrees Fahrenheit) over the affected areas, co-author Holly Maness from the University of Toronto told AFP. "The increased surface temperatures we observe are relatively large and may be sufficient to drive further changes in regional climate, such as changes to circulation, cloud cover and precipitation," she said. "The effects of climate change cascade. Previous studies have shown that climate change has allowed the beetle to flourish." The beetle infestation ranks among the largest ecological disturbances ever recorded in Canada, said the team, adding that similar outbreaks were also claiming large forested areas in the western United States. "The current mountain pine beetle outbreaks serve as a parable, illustrating how the delicate balance of processes imposed by a stable climate can be easily disrupted by climate change," said Maness.