The Menai Strait whitebeam is a shrub or small tree at least 10 metres tall. It is found in open areas of mixed woodland on limestone rock by the shore of the Menai Strait, in the Nant Porth Site of Special Scientific Interest (SSI); it is endemic to this tiny area of the north Wales coast.

The whole population contains about 30 plants, most of which are reproducing and grow in an area that is probably less than 0.1 km². Its tiny distribution and its location within a 10 metre wide strip along the coast means that future sea level rise could be a significant threat to this species. It has therefore been classified as Critically Endangered.

For a long time known only as “Sorbus, un-named taxon from the Menai Strait”, the whitebeam had been known to be different from other species for a considerable period. The earliest herbarium specimens of this species were collected in 1879 by W. H. Painter, however, until 2014 (when it was formally named Sorbus arvonensis) it went through a period of being thought part of three other closely related whitebeam species; S. porrigentiformis, S. eminens and S. hibernica.

Whilst the Menai Strait whitebeam has not traditionally been used by the people of North Wales, the proximity of its home, in the North Wales Wildlife Trust’s Nant Porth Nature Reserve, to the University at Bangor and the town of Menai Bridge make its habitat an important recreational area. The site was once quarried and the woodland behind its immediate coastal strip was planted. Where coastal erosion and treefall take place, the Menai Strait whitebeam takes advantage of the additional light and colonises these open areas readily, although it is always within sight of the sea.

Whilst large-scale coastal erosion caused by climate change-induced sea level rise, is likely to have a detrimental impact on the species, smaller scale and one-off erosion events certainly prove positive for this species. Mimicking this, by creating space in the canopy through selective removal of more common species, could give Sorbus arvonensis the chance to flourish.

The species was assessed as Critically Endangered in 2017 as part of a Global Trees Campaign workshop to review 190 assessments of European Sorbus. The workshop brought together eight Sorbus experts from across Europe in Zagreb, Croatia, who identified that almost 75% of European Sorbus are threatened with extinction. Not everybody considers Sorbus species as a high priority for conservation action because they can evolve quickly and readily form new species. However, conservation action for Sorbus can be achieved on a relatively low budget and Whitebeam species are important ecologically, for the large number of other species that they support; including birds, pollinators and as the food plant for several species of moth.

A collaboration between FossilPlants and The National Botanic Garden of Wales, with assistance from the North Wales Wildlife Trust, is working to understand the Menai Strait whitebeam’s cultivation so this species can be conserved in botanic gardens and seed banks and one day, if needed, be restored to the wild.

This profile was written by Robbie Blackhall-Miles. Main photograph by Robbie Blackhall-Miles.

Find out more about this project: http://www.fossilplants.co.uk/menai-strait-whitebeam/