Building resilience in wild Scottish wych elm (Ulmus glabra)
Wych elms that have survived the epidemic of Dutch elm disease are being used to assist recovery driven by natural processes in Scottish upland native forest restoration.
In common with the rest of Europe, Scotland’s population of mature wych elms has declined severely since the arrival of an aggressive form of Dutch elm disease (Ophiostoma novo-ulmi) in the 1970’s. Surprisingly, wych elm is not classified as threatened in the UK. However, some northern European countries have recognised the serious threat to the ecological role of wych elm as a component of mixed broadleaved woodland on base-rich soils in the upland fringe.
To assist the recovery of wych elm, and build resilience in wild populations, a three-year Scottish Government-funded project at the Royal Botanic Garden Edinburgh is identifying promising trees and using them to breed a new generation that may be better adapted to coping with disease. The approach taken is different from traditional tree breeding, which results in a few ‘elite’ clones that often have complex hybrid parentage involving non-native species. By searching for resilience in native elms, maximising genetic diversity and relying on natural processes to select the most adapted trees, the potential for sustained, natural recovery is enhanced.
Two cycles of controlled pollinations involving 12 parent trees that met criteria for size and proximity to disease have produced 2,750 seedlings. These will be planted at ecologically suitable sites across Scotland in 2025, often to enhance existing elm populations. The parent trees were found during a public ‘wych hunt’ in southern Scotland. The area for the hunt was chosen as it has had decades of exposure to disease. By moving the genetic resource to where it is needed most, including beyond the advancing front of disease, the project has ignored provenance zones. This decision was reached by weighing the pros and cons and considering the likely severe losses from the ongoing spread of disease. The possibility that the vector of disease, elm bark beetles, may benefit from more regular heatwave conditions due to climate change was also considered.
This project has been supported by the Scottish Governments Nature Restoration Fund, administered by NatureScot. It is part of wider work to assist the recovery of 10 threated native Scottish Plants. Read the blog of the Scottish Plant Recovery project:
This article was originally written by academic researcher and science communicator Max Coleman (Royal Botanic Garden Edinburgh).
