To the Norse, it was the tree of life. Vikings called themselves, Aeslings, men of ash, believing that the first man was made from an ash tree. The universe, they believed, spins on an ash tree axis, Ygddrasil, the world tree, which has earth in its roots, and heaven in its canopy. Legend says that when the ash trees die, so will we. Little wonder therefore that when the ash dieback disease struck in Denmark, it caused deep fear about how much we have destabilised our life support systems on earth.