Both the Mendips and the Quantocks have been badly hit by ash dieback in the last few years, with Somerset County Council and its successor Somerset Council having to remove and replace large numbers of trees to prevent the disease from spreading.

Source: https://www.bridgwatermercury.co.uk/news/23955776.somersets-protected-spaces-re-branded-national-landscapes/?ref=rss

T1 Magnolia - Fell, poor condition with dieback, damaging adjacent wall.

Source: https://www.salisburyjournal.co.uk/news/23974957.salisbury-district-planning-applications-round-up/?ref=rss

The importance of genetic diversity for adaptation to changing conditions can be illustrated by the threat posed by ash dieback.

Source: https://www.heraldscotland.com/news/23361198.new-strategy-gets-root-scotlands-biodiversity-crisis/?ref=rss

This will give the best chance for ash seedlings that may be resistant to ash dieback to grow, and any trees with resistance to live on.

Source: https://www.newsandstar.co.uk/news/23866549.tree-disease-triggers-partial-closure-smardale-nature-reserve/?ref=rss