OVER the past 14 years, a tiny insect no bigger than a grain of rice has laid waste a swathe of British Columbia's forests so vast that the rust-red wasteland is visible from space. The mountain pine beetle has infested and killed over half the lodgepole pine forest in the centre of the province—an area larger than England. It has rampaged eastwards into northern Alberta for the first time. (It has also made localised attacks on forests in all 11 western American states.) Scientists now fear the voracious beetle is about to invade the jack pines of the boreal forest, which could see the plague sweep across northern Canada to the Atlantic coast. It is an unprecedented infestation that could become a catastrophe.

The pine beetle is a well-known pest, not an exotic import, but no effective means has been found to stop it. The beetles swarm up trees in large numbers, killing them by boring through the bark, sapping their nutrients and emitting a damaging blue fungus. Cold winters and forest fires normally keep the beetle populations in check. Some forest scientists trace the current outbreak to 1994, when provincial-government foresters, fearing the ire of greens, failed to eradicate a small infestation in a provincial park by cutting and burning. In any event, recent British Columbian winters have not been cold enough to kill the beetles.

The infestation is gathering pace: foresters fear that by 2013 four-fifths of British Columbia's central-southern pine forest will be gone. Wafted eastwards by strong winds, in 2002 the beastie made its debut in northern Alberta and further south in the national parks of Jasper, Banff and Kananaskis on the eastern slopes of the Rocky Mountains. It has advanced 400 kilometres (250 miles) across the province to Slave Lake. The beetle is now established in Alberta, despite vigorous cutting and burning.

It is closing in on the vast boreal forest. It is only 100km from the nearest outbreak, and winds can carry newly-hatched pine beetles up to 300km a year, notes Allan Carroll of the Canadian Forest Service. The boreal forest is mainly composed of jack pines, which lack the natural defences of the lodgepole pine; this has evolved in coexistence with the beetles.

The hope is that the infestation will stall on Alberta's eastern border with Saskatchewan, where large stands of jack pine are scarce. Better still would be a long, bitterly cold winter like those that were common until the 1980s. “Climate change is unequivocally affecting the outbreak,” says Mr Carroll. They may be big energy consumers, but many western Canadians have also started to worry about what carbon emissions may be doing to their beloved forest.