Betula chichibuensis critically endangered, conservation efforts may not be enough

Betula chichibuensis is classified as critically endangered on the IUCN Red List due to its extreme rarity and limited range

by Lorenzo Ciotti
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Betula chichibuensis critically endangered, conservation efforts may not be enough

Betula chichibuensis is classified as critically endangered on the IUCN Red List due to its extreme rarity and limited range In 1993, only 21 trees existed in the wild. Although several other small populations of the tree have been discovered in the 2010s, including Kitakami populations, Chichibu birch remains very rare.

Ex situ conservation efforts to prevent the species from becoming extinct are ongoing, including at the University of Liverpool's Ness Botanic Gardens and Bedgebury National Pinetum. Chichibu birches are extremely rare in nature, growing only on a handful of limestone outcrops in the mountains of the Japanese island of Honshu.

From their first description as a distinct species by Hiroshi Hara in 1965 until about 2015, B. chichibuensis had been found exclusively in a single stand in the Okuchichibu Mountains, where there were only 21 Chichibu birches.

counted in 1993. As of 2017, Dr. Toshihide Hirao has found at least eight other small schools of B. chichibuensis, mostly in the Kitakami Mountains of northeastern Honshu. A 2014 expedition to the Okuchichibu Mountain Locality found B.

chichibuensis growing on an exposed limestone mountain face near the Karisaka Tunnel, alongside plants including Sasa bamboo, Chamaecyparis obtusa cypress, Juniperusrigid juniper, and Acer pictum maples. Betula chichibuensis is considered a critically endangered species by the IUCN Red List.

In addition to Chichibu birch's self-incompatibility and low seed viability, the species is also threatened by habitat degradation and deforestation in the Chichibu District, and its small population size makes it particularly vulnerable to natural disasters and disease .

In the Royal Botanic Gardens, UK, site of the first B. chichibuensis ex situ conservation program outside Japan, serious ex situ conservation efforts to prevent the extinction of the Chichibu birch began in 1986, when Tetsuo Satomi collected seeds from the Okuchichibu Mountains site and sent them to Hugh McAllister, a botanist at the University of Liverpool's Ness Botanic Gardens.

Eight of the seeds germinated, the clippings of which were then used to create all of the Chichibu birches growing in captivity through the 2010s. Cultivated specimens vary significantly in appearance, with some clones exhibiting a spreading habit and others growing more upright.

In 2014, an Anglo-Japanese expedition to the Okuchichibu Mountains collected around 1,000 seeds in order to increase the genetic diversity of cultivated specimens. As of 2015, more than 30 gardens around the world grow Chichibu birches, including Bedgebury National Pinetum and Harvard University's Arnold Arboretum.