Chichibu Birch (Betula chichibuensis – Hara 1956)

The Chichibu District of Honshu Island, Japan. Photo taken from Wikipedia.

Status – Critically Endangered

Perhaps one of the world’s rarest trees given that there is estimated to be fewer than 50 specimens still occurring in its native range of Honshu Island, Japan.  However, surprisingly, the species is rather easily available as an ornamental addition to gardens around the world.  Thus, despite the fact that the situation of the species in the wild remains critical, it is openly traded on the horticultural market and this fact may play a role in the lack of impetus to reinforce the wild population to levels where it can be deemed secure.  As is the case for any tiny isolated population, fire, disease, a catastrophic geological event or over-zealous harvesting could completely wipe out the species in the wild.  On a positive note though, the species does seem to be quite tolerant to broad environmental conditions – surviving both drought and wet soil – suggesting that it could readily adapt to climate change, which is a growing threat.  Firmly rooted to the bottom of the birch phylogenetic tree, this endemic Japanese birch is a relic of the earliest evolutions of the genus.  Although having an appearance typical of birch trees globally, it tends to grow as a multi-stemmed shrub more so than a tree.  Crucially, the Chichibu Birch is self-incompatible meaning that it cannot reproduce in isolation and needs to occur in multi-specimen groups to ensure a self-sustaining population.  Currently, this is not really the case, raising the prospect that the wild population will require on-going human intervention through assisted reproduction to manage the mountain population much in the same way as the global horticultural population is administered.  Thus, while the horticultural trade ensures this tree’s future by acting as a source for reinforcement of the wild population and at least endowing a global profile on the species, greater attention needs to be focussed on bolstering the security of this birch species within its native range through judicious planting and habitat protection.