Botanic gardens and the conservation of tree species.

The general role of botanic gardens in plant conservation has been widely accepted since the 1970s and many threatened plant species are now in well-documented living collections and seed banks. Conserving tree species in ex situ collections still presents particular challenges. Many trees have so-called 'recalcitrant' seeds that cannot be stored in conventional seed banks and the sheer size of living trees restricts the number of individuals of a particular species that can be grown in a botanic garden. Even if space is available, is ex situ conservation a desirable option and how does this compare with conserving tree species in their natural habitats? In reality, conservation action for globally threatened tree species, by either in situ or ex situ means, remains inadequate and steps should be taken to combine approaches to prevent the urgent loss of tree species worldwide.