Of all our childhood memories, few are quite as thrilling, or as tactile, as those of climbing trees. Scampering up the rough trunk, spying on the world from the cool green shelter of the canopy, lying on a limb and looking up through the leaves at the summer sun almost made it seem as if we were made for trees, and trees for us.Even in adulthood, trees retain their power, from the refreshing way their waves of green break the monotony of a cityscape...