Globe and Mail: Baffin Island is covered with an austere, Arctic tundra now, but some time later this century it will be capable of sprouting something unusual: a verdant coniferous forest. The idea that trees might some day spread to many parts of Canada’s Far North may seem unlikely, but it is being touted as a realistic possibility in one of the most extensive looks at how the world’s forests will cope with further global warming. Call it a climate-change paradox: While the overall …