Helping Europe’s forests adapt to climate change

One of the key objectives of the EU-funded FORGER project was to bring to the fore the issue of genetic diversity; a subject that has often been overlooked by policy-makers and forest managers in favour of the more tangible subject of biodiversity.

Biodiversity concerns various levels, from ecosystems to genes. While species diversity is clearly visible when you walk through a forest and observe the trees within it, genetic diversity describes the biological differences between trees of the same species and can’t be observed without specialist equipment.

Yet genetic diversity forms the base for species adaptation and must be conserved to ensure the long-term stability of Europe’s forests, especially in the context of climate change.

Credit: Bioversity International/B.Vinceti“Just because you are protecting biodiversity doesn’t mean you are protecting genetic diversity,” warns Dr. Bernd Degen, of the Institute for Forest Genetics.

In other words, a biodiverse forest, though rich in species, may host tree populations that are less genetically diverse than a forest with fewer overall species. Thus, you cannot tell whether a forest is better ‘equipped’ to face climate change without screening into the genetic dimension.

Preserving genetic diversity is essential if forests are expected to adapt to warmer and drier conditions. But FORGER, which presented its findings at its final project meeting in Dublin (17 November 2015), stressed the importance of committing more research to monitoring forest genetic resources (FGR) in areas earmarked for conservation.

“The success of initiatives to preserve biological diversity under impending climate change will largely depend on our capacity to identify and understand how adaptive variation [the variation that exists within a species and enables it to adapt] in keystone species is distributed and evolves,” explains Dr. Degen.

Another objective of FORGER was to map the historic movement of forest reproductive material (FRM) – seeds, cones, cuttings and planting stock – of certain tree species across Europe.

This was something that has not been done before and the results were enlightening. Piecing together data, some of which went back to the Doomsday Book, scientists provided evidence, for the first time, detailing the magnitude of movement of forest reproductive material across Europe (or at least across the countries in Europe that have records still available and sufficiently detailed) for certain tree species.

“People assume that EU forests have a high degree of naturality, but in many cases they have been significantly altered by man,” says Prof. Thomas Geburek. “The natural gene pool of many of Europe’s forests has been changed by the movement of FRM.”

FORGER found that human activity started to significantly alter tree composition in Europe in the 18th century. At this time the distribution of broadleaf species was significantly reduced in Central Europe, while the distribution of Norway spruce was enlarged by translocations, especially in Germany, Poland, England, France and Belgium.

World War II and the ensuing decades accelerated the process of deforestation, further reducing the distribution of certain autochthonous species.

Any afforestation that has followed might have reversed some of the losses to Europe’s tree cover, but, even where species have been replaced like-for-like, this human activity has significantly altered the gene pool. This manipulation has not always been positive.  

“It is important to mention, though, that not all translocations of FRM have had a negative impact on forest growth,” says Prof. Geburek. “If appropriate material is translocated this may even enhance the productivity of forests or the ability of tree populations to withstand climate change.”

Essentially, then, forest managers could prepare for warmer temperatures by introducing trees that currently live in similar conditions to those expected in the future. And not just any trees: trees of the same species, rather than another species, whose introduction would significantly modify interactions with other species in the forest ecosystem.

Prof. Csaba Mátyás, of the Hungarian Academy of Sciences, and Dr. Koen Kramer, FORGER project coordinator, discussed the benefits of assisted migration in their paper, Adaptive Management of Forests and Their Genetic Resources in the Face of Climate Change.

“Local FRM is not always showing the best performance. Assisted migration of tree populations through transfer of FRM could help sustain healthy and productive forests,” they argue. “The transfer of FRM, though, does not always solve all problems. In addition, some areas should be left to evolve without such an active management measure, to allow natural selection to operate.”

In the short-term, forest managers should be judicious about the provenance of the FRM they are using, seeking expert advice where possible. In the long-term, policy-makers and forest managers must work together to ensure the transfer of FRM is properly documented and that the performance of translocated material is accurately monitored.

“A regulatory framework on FRM documentation is in place,” says Prof. Geburek. “I do not understand why it is not being closely adhered to.”

Given climate change the transfer of FRM in Europe is likely to increase and FORGER indicates the need to strengthen the implementation of existing regulations and to harmonise data on transfer of FRM across EU member states.

Written by Gavin Haines