"Yggdrasill is a model for our environment that we would do well to think about," says Larrington. "It represents a natural world that is giving but cannot be taken for granted: a symbiotic system that may – or may not – withstand all the depredations that humanity inflicts upon it."
The implicit warning is especially pertinent now, given that Yggdrasill is not just any tree but an ash tree. "It was silver-grey," writes Neil Gaiman in his myth-infused 2001 novel American Gods. "Spectral and yet utterly real." You have only to walk through one of the many forests across the globe recently ravaged by ash dieback disease, to see vast ghostly clearings, where utterly real silver-grey trees recently stood.