From the summit of Katahdin, the view is of forests stretching in all directions. …Forty-five years ago this scene would have been quite different. A voracious insect called the spruce budworm was ravaging Maine’s North Woods, killing mountainsides of balsam fir and red spruce. …Today, foresters and landowners are nervously tracking a renewed spruce budworm presence in the North Woods. The insects have already stripped hundreds of thousands of forest acres in Quebec and Ontario. After decades of heavy logging, scattered tracts are being managed with ecological timbering methods that strive to maintain natural systems — but most are not. Questions abound over how the state’s forests, both the northern timberlands and smaller, privately owned tracts throughout the state, will fare in a world beset by climate change. …And there’s the coming spruce budworm invasion.