Ash disease shows need for diversity

The fungus has had a devastating impact in some European countries, affecting 90% of Ash trees in Denmark.

It was first spotted on the island in 2012 in a consignment of trees that was destroyed, prompting an import ban to be imposed.

But that has not proven enough to stop the infection which is now established in at least seven sites.

Eradication efforts would not prevent it spreading and there is no treatment.

Despite that grim prognosis, there is hope that encouraging genetic variation by planting new Ash trees and letting older ones set seed will help ensure this species, one of the most important native trees for wildlife, can still thrive.

That is important, not only for dependent species such as the Centre-barred Sallow moth whose population is likely to decline in line with Ash numbers, but also for the island’s environment’s ability to withstand other diseases.

In the 1990s Guernsey learnt just how vulnerable it was when Dutch elm disease destroyed its tree cover. Today we still benefit from the tree planting programme that was implemented to ensure a diverse range of species, the risk of having one dominant type of tree having been so brutally exposed.

Guernsey’s woodland is young, little pre-dates the Second World War, when many trees were cleared, and according to the last habitat survey from 2010, Sycamore dominates with a high presence of oak and ash. From 1999 until that survey, the amount of woodland grew 2.6%, to cover 379.4 ha.

Work is now under way on a new survey which will show how habitats have changed over the last decade.

It will expose whether any are at particular risk and hopefully therefore become a basis for how to address that through wider States policy and other initiatives.

Without this type of work it is all too easy for a slow creep of habitat loss to take hold without being noticed.