Beetles, wildfire work together to ravage northern forests

A veil of smoke settled over the forest in the shadow of the St. Elias Mountains, in a wilderness whose spruce trees stood tall and gray, a deathly gray even in the greenest heart of a Yukon summer. "As far as the eye can see, it's all infested," forester Rob Legare said, looking out over the thick woods of the Alsek River valley. Beetles and fire, twin plagues, are consuming northern forests in what scientists say is a preview of the future, in a century growing warmer, as the land grows drier, trees grow weaker and pests, abetted by milder winters, grow stronger. Dying, burning forests would then only add to the warming. Along with shrinking the polar ice cap and thawing permafrost, scientists say, the warming of the Arctic threatens to turn boreal forest -- the vast cover of spruce, pine and other conifers blanketing these high latitudes -- into less of a crucial "sink" absorbing carbon dioxide and more of a source, as megatons of that greenhouse gas rise from dead, burning and decaying wood...AP