SEK 25 million for research to save the ash tree

The European ash has declined dramatically across Europe due to ash dieback disease, and in Sweden the species is now classified as endangered. At the same time, another serious threat is approaching - the emerald ash borer, one of the world’s most destructive insect pests of ash trees.

Two complementary research projects at SLU have now received funding from Formas. Their aim is to develop the knowledge and practical tools needed to restore resilient ash populations and secure the future of one of Sweden’s most ecologically important broadleaf tree species.

From resistant trees to resilient ash populations

The larger project has been awarded SEK 15 million to develop Sweden’s first comprehensive framework for ash restoration. Led by Michelle Cleary, Associate Professor of Forest Pathology, the project builds on more than a decade of research within the national Save the Ash initiative and combines genetics, ecology, forest management, and policy research.

- We want to answer a critical question: how can we restore ash populations that are not only resistant to ash dieback but also genetically diverse enough to cope with future challenges? says Michelle Cleary.

A central component of the project is Sweden’s first coordinated ash restoration trials, so-called living labs, which will be established in collaboration with Sveaskog. Researchers will monitor how resistant ash seedlings establish and develop under real-world forestry conditions.

The goal is to produce recommendations for future restoration efforts, including where ash should be planted, which tree species it should be grown alongside, and how different forest management practices influence restoration success. The researchers will also determine which approaches work best under different local conditions.

Another key objective is to investigate how resistant trees can be used in breeding and restoration without reducing genetic diversity. This is particularly important in Sweden, where ash occurs at the northern edge of its natural range. Swedish ash populations already have relatively low genetic diversity and have been among the hardest hit by ash dieback in Europe.

- Greater genetic diversity improves the population’s ability to cope with environmental change, such as a warmer climate, as well as new threats like the invasive emerald ash borer, which is likely to reach Sweden in the future. An important part of our project is identifying trees that show resistance to both threats, says Michelle.

Using genetics to strengthen the ash trees of the future

The second project has been awarded SEK 9.5 million to produce the first comprehensive assessment of the genetic diversity of Swedish ash. The project will provide researchers with a stronger scientific basis for conserving and breeding resistant trees.

Led by Professor Levi Yant, the project builds on a previous collaboration with the Royal Botanic Gardens, Kew. Researchers will identify the genetic variation that enables some ash trees to withstand ash dieback better than others. This knowledge can then be applied to future ash breeding programmes.

- The resistant ash trees identified through the Save the Ash initiative represent a unique resource. Through our collaboration with the Royal Botanic Gardens, we can now use genetics to uncover variation that has previously been hidden from us. This knowledge opens up entirely new opportunities to develop tools for breeding, says Levi Yant, Professor of Plant Genetics at SLU.

Two projects – one shared goal

Although funded separately, the two projects are designed to complement one another. One project will identify the genetic traits that make certain ash trees resistant to ash dieback and develop new breeding tools. The other will translate this knowledge into practice through restoration trials and studies of natural regeneration. The projects will be carried out in close collaboration with Skogforsk, Sveaskog, and several other partners.

- Saving the ash is not simply about producing resistant trees. It is about rebuilding resilient populations that can survive, reproduce, and adapt to future challenges. Together, these projects provide the tools needed to achieve that, says Michelle Cleary.

- Together, the projects will help translate more than ten years of research into practical solutions for the future of ash. Our hope is that today’s resistant ash trees will lay the foundation for tomorrow’s ash forests, says Levi Yant.