Surrounded by the feral goats and Soay sheep of Cheddar Gorge are some of the UK's rarest and most critically endangered trees nestled on cliff edges.

To reach the 10 Fay's whitebeam trees, volunteers of all ages have to climb up the gorge and Burrington Combe in the Mendip Hills, Somerset, which are the only places nationally the species grows.

They are making the steep ascent alongside experts and conservationists who are working with chiefs at Westonbirt Arboretum in Gloucestershire as part of a new scheme to collect the trees' seeds.

Libby Houston, an 84-year-old botanist among the people climbing cliff edges to help save the trees, said: "[If] there's a disease around, it is a worry. They could be wiped out and that could be the end."

The trees are among 21 which are critically endangered across the UK and Ireland, according to the latest International Union for Conservation of Nature Red List of Threatened Species update in July.

Rosie Anderson, tree conservation manager at Westonbirt, said the species was very special to Somerset.

"They're really important for the ecosystem. They can grow on these steep cliffs, that means they're a very valuable source for birds and animals."

She said the species' "restricted populations" means any threats to their future "could be heightened", adding they are "vulnerable to pests, disease and grazing".

Anderson is among numerous conservationists who are collecting seeds from the trees to take back to Westonbirt's botanic gardens as a "back up".

It is part of a wider effort to prevent the loss of the threatened sorbus species - which also includes rowans and service trees.

"There are no banked seeds, and no trees growing in gardens," she said.

"We really want to make sure we've got a good back up of that material in conservation.

"Ideally we'll keep this population healthy and thriving, but it's always good to have material in botanic collection just in case anything happens and we can potentially re-introduce them in the future.

"It's to keep them safe going into the future with all the unknown threats that could come our way."

Houston added she had to work hard to keep up with the some of the younger volunteers.

"I'm lucky, my sense of balance could go but it hasn't yet. Touch wood.

"I'm really interested in the rare trees and how they present themselves," she said.

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