The £15 billion cost of ash dieback in Britain

Summary Invasive tree pests and diseases present some of the greatest global threats to forests, and the recent global acceleration in invasions has caused massive ecological damage 1 , 2 . Calls to improve biosecurity have, however, often lost out to economic arguments in favour of trade [3] . Human activities, such as trade, move organisms between continents, and interventions to reduce risk of introductions inevitably incur financial costs. No previous studies have attempted to estimate the full economic cost of a tree disease, and the economic imperative to improve biosecurity may have been underappreciated. We set out to estimate the cost of the dieback of ash, Fraxinus excelsior, caused by Hymenoscyphus fraxineus, in Great Britain, and investigate whether this may be the case [4] .