Conservation has long been about protecting communities of plants and animals where they are. But climate change is leading to a nascent form of conservation that embraces change and instead seeks to provide a thriving stage on which it can happen. Chester, Mass. — It’s a late-July morning, and Andy Finton works his way up a trail in western Massachusetts’ Berkshire Hills, walking beneath a canopy of sugar maple, ash, beech, and basswood. At one…