SNH: plan now to preserve ancient rainforest species

Western Scotland is home to temperate rainforests inhabited by rich and diverse lichen communities. Most of them are ‘epiphytes’ which means they grow on another plant without harming it.

Lichens will, like the rest of Scotland’s biodiversity, be affected by climate change. Since they depend on the trees they grow on, they could also be threatened by anything that harms the trees – including diseases such as ash dieback.

The new report ‘Woodland composition, climate change and the long-term resilience of lichen epiphytes at Glasdrum NNR’ presents a method that can help land managers to consider how decisions taken now could affect the future survival of species.

The SNH-managed Glasdrum National Nature Reserve (NNR) was selected as it is an example of Scotland’s internationally important temperate rainforest characterised by diverse oceanic lichens.

The method uses climate change predictions, and detailed knowledge of the individual species, to predict whether the changing climate is likely to help or hinder the species’ growth in future. It also allows woodland managers to explore what might happen if a disease, such as ash dieback, wiped out one or more species of tree or if management promoted the regeneration or planting of other species.

Dr David Genney, SNH’s lichen specialist, said: “Western Scotland’s clean air, relatively mild winters, relatively cool summers and year round rainfall have created a diversity of lichens that is unparalleled elsewhere in Europe. Their international significance should not be underestimated.”

Dr Chris Ellis of RGBE, the report’s lead author, said: “This new tool is not intended to predict the future, but it does allow SNH to explore risks that we are concerned about – climate change and tree disease – and to identify contingency plans that maximise the chance that woodland lichens survive in the long-term.”

Jeanette Hall, SNH’s woodland advisor, said: “Many woodland species require old trees and some are also quite specific about the type of old tree they can grow on. This presents us with a challenge because woodland management decisions taken now have to be robust enough to deliver old trees more than a hundred years in the future – a lot can happen in that time.”

Of the range of scenarios tested, promotion of oak regeneration would be most likely to help the majority of Glasdrum’s priority epiphyte species. In particular, this management would create resilience in the lichen flora against the potential loss of ash through ‘ash dieback’.

The report cautions against a single strategy because it is impossible to predict all future events. For example oak could be affected by an as yet unknown disease in the future so investing solely in oak regeneration would be a mistake.