CLIMATE CHANGE IMPACTS ON FORESTS 

Martin BRAUN and Katharina LAPIN 

Projections show that climate change will have a considerable impact on trees in forests by altering the frequency, intensity, duration, and timing of factors including precipitation, drought, non-native species, insect and pathogen outbreaks, wind and ice damage, and gravitational mass movement (Dale et al., 2001). Trees are believed to have limited adaptive capacity to respond to extreme temperatures and rapid climatic and environmental change (Lindner et al., 2010). Furthermore, climate change is expected to be one of the main future causes of biodiversity loss worldwide (Sala, 2000), and research shows that the extinction of species from numerous taxa will follow (Thomas et al., 2004). It is by now widely accepted that climate change is a global phenomenon, that CO2 emissions are the main cause of climate change, and that deforestation is currently responsible for almost 20% of the annual global emissions of CO2 (Diamandis, 2014). 

The impacts of climate change are expected to be particularly severe in the Alpine region. A shifting precipitation regime will likely lead to more intense and frequent drought events during summers (Fenning, 2014). Droughts tend to lead to reductions in growth and CO2 uptake in subsequent years (e.g., summer drought study conducted by Ciais et al., 2005), and successive drought events likely affect tree quality and increase mortality, leading to changes in species composition and forest structure. Another challenge in the Alpine region is the likely increase in mean temperature, which will cause increased evaporation and thus further changes to precipitation patterns, potentially resulting in even more severe drought episodes impacting forest growth and resilience (Fenning, 2014). Although forest fires are currently not a pressing problem in the Alpine space, fire intensity and frequency are also likely to increase (Dale et al., 2001). On a large scale, forest tree species and communities will 12 Climate Change Impacts On Forests 

experience increased stress, and cultivation will no longer be possible in lowland areas, thereby strongly affecting some habitats and possibly leading to impacts on biological diversity. The ideal climate zones for many tree species in Europe will shift northwards and upwards. For the Alpine regions, this implies that climate change will further alter the distribution of many species, with an upward shift in elevation for various plant communities (Hastings and Turner, 1965) and earlier onset of spring (according to phenological observations) for most tree species. So-called ecologically effective population densities serve as guidelines for determining the minimum densities of individuals necessary to maintain critical interactions and ensure resilience against ecosystem degradation and extreme events (Soule et al., 2003). 

Adaptation requirements for forests 

Non-native trees (NNT) are sometimes viewed as part of a solution for adapting forests to future climate conditions. Bioclimatic envelope modelling (e.g., Araújo and Peterson, 2012; Pearson and Dawson, 2003) can help to provide a first assessment of NNT viability under expected conditions. Subsequently, factors such as biotic interactions, soil conditions, extreme sites, evolutionary change, dispersal ability, and adaptation potential of native tree species to future climatic conditions must also be appropriately considered (Araújo and Peterson, 2012; Pearson and Dawson, 2003; Sutmöller et al., 2008), along with the fact that large areas of forests in the Alpine space are secondary forests and do not reflect the potential natural distribution (Brune, 2016). 

Since no significant effort has been made during the past two decades to mitigate habitat loss and protect biodiversity, it is likely that more areas will need to be set aside for conservation to increase the resilience of forests to stochastic climatic events. Safeguarding and increasing biodiversity is seen as an important step in boosting the resilience of Alpine space forests to future climatic conditions. The introduction and use of NNT will play an ambiguous role in this context, since their introduction in conservation areas can have undesirable and unintended effects on the resilience of 13 Climate Change Impacts On Forests 

habitats. Potential positive use cases, on the other hand, can support the stabilization of ecologically compromised areas and ensure a consistent raw material supply under future climatic conditions. 

The forest-based sector will likely have to adapt economically due to changes in requirements for suitable trees, which will lead to a decline in softwood available for further processing. This in turn will create a need for research and development regarding hardwood processing technologies, as well as adaptation to a wider variety of tree species in general to optimally use and allocate the available biomass supply. In this context, adaptation requirements in the Alpine space include the cultivation of suitable tree species from similar habitats in climatically appropriate regions (i.e., assisted migration), respectively the introduction of NNT. 

Regarding the selection of trees for future use, the effects of environmental factors on tree resistance to insects (in direction and intensity) seem to depend on available resources, the intensity of stress supported by the individual tree species (i.e., its resilience), and the nature of specific insect guilds (i.e., groups of species that exploit the same resource in related ways) (Lieutier, 2006). Important steps to consider in terms of forest management are therefore: 

Investigation of potential climate-induced habitat dynamics and efforts to designate more areas for conservation as well as some for intensification. 

Careful examination of current and future climatic suitability of currently employed propagation material. 

Investigation of ecosystem risks, benefits, and trade-offs of introducing established species from different provenances vs. NNT. 

Analysis of potential habitat effects caused by the introduction of NNT. 

Ensuring that prerequisites and intended targets are met in forests available for wood supply as well as conservation areas.

14 Climate Change Impacts On Forests 

Literature 

Araújo, M.B., Peterson, A.T. 2012. Uses and misuses of bioclimatic envelope modeling. Ecology 93, 1527–1539. https://doi.org/10.1890/11-1930.1 

Brune, M. 2016. Urban trees under climate change. No. Report 24. Climate Service Center Germany, Hamburg. 

Ciais, Ph., Reichstein, M., Viovy, N., Granier, A., Ogée, J., Allard, V., Aubinet, M., Buchmann, N., Bernhofer, Chr., Carrara, A., Chevallier, F., De Noblet, N., Friend, A.D., Friedlingstein, P., Grünwald, T., Heinesch, B., Keronen, P., Knohl, A., Krinner, G., Loustau, D., Manca, G., Matteucci, G., Miglietta, F., Ourcival, J.M., Papale, D., Pilegaard, K., Rambal, S., Seufert, G., Soussana, J.F., Sanz, M.J., Schulze, E.D., Vesala, T., Valentini, R. 2005. Europe-wide reduction in primary productivity caused by the heat and drought in 2003. Nature 437, 529–533. https:// doi.org/10.1038/nature03972 

Dale, V.H., Joyce, L.A., Mcnulty, S., Neilson, R.P., Ayres, M.P., Flannigan, M.D., Hanson, P.J., Irland, L.C., Lugo, A.E., Peterson, C.J., Simberloff, D., Swanson, F.J., Stocks, B.J., Michael Wotton, B. 2001. Climate Change and Forest Disturbances. BioScience 51, 723. https://doi. org/10.1641/0006-3568(2001)051[0723:CCAFD]2.0.CO;2 

Diamandis, S. 2014. Forests Have Survived Climate Changes and Epidemics in the Past. Will They Continue to Adapt and Survive? At What Cost? In Fenning, T. (ed.), Challenges and Opportunities for the World’s Forests in the 21st Century. Springer Netherlands, Dordrecht, pp. 767–781. https://doi.org/10.1007/978-94-007-7076-8_34 

Fenning, T. (ed.). 2014. Challenges and Opportunities for the World’s Forests in the 21st Century, Forestry Sciences. Springer Netherlands, Dordrecht. https://doi.org/10.1007/978-94-007-7076-8 

Hastings, J.R., Turner, R.M. 1965. The changing mile: an ecological study of vegetation change with time in the lower mile of an arid and semi-arid region. University of Arizona Press, Tucson, Arizona. 

Lieutier, F. 2006. Changing forest communities: Role of tree resistance to insects in insect invasions and tree introductions. In Invasive Forest Insects, Introduced Forest Trees, and Altered Ecosystems. Springer Netherlands, Dordrecht, pp. 15–51. 

Lindner, M., Maroschek, M., Netherer, S., Kremer, A., Barbati, A., Garcia- Gonzalo, J., Seidl, R., Delzon, S., Corona, P., Kolström, M., Lexer, M.J., Marchetti, M. 2010. Climate change impacts, adaptive capacity, and vulnerability of European forest ecosystems. Forest Ecology and Management 259, 698–709. https://doi.org/10.1016/j.foreco.2009.09.02315 Climate Change Impacts On Forests 

Pearson, R.G., Dawson, T.P. 2003. Predicting the impacts of climate change on the distribution of species: are bioclimate envelope models useful? Evaluating bioclimate envelope models. Global Ecology and Biogeography 12, 361–371. https://doi.org/10.1046/j.1466- 822X.2003.00042.x 

Sala, O.E. 2000. Global Biodiversity Scenarios for the Year 2100. Science 287, 1770–1774. https://doi.org/10.1126/science.287.5459.1770 

Soule, M.E., Estes, J.A., Berger, J., Del Rio, C.M. 2003. Ecological Effectiveness: Conservation Goals for Interactive Species. Conservation Biology 17, 1238–1250. https://doi.org/10.1046/j.1523-1739.2003.01599.x 

Sutmöller, J., Spellmann, H., Fiebiger, C., Albert, M. 2008. Der Klimawandel und seine Auswirkungen auf die Buchenwälder in Deutschland (No. 3), Ergebnisse angewandter Forschung zur Buche. Nordwestdeutsche Forstliche Versuchsanstalt, Göttingen. 

Thomas, C.D., Cameron, A., Green, R.E., Bakkenes, M., Beaumont, L.J., Collingham, Y.C., Erasmus, B.F.N., de Siqueira, M.F., Grainger, A., Hannah, L., Hughes, L., Huntley, B., van Jaarsveld, A.S., Midgley, G.F., Miles, L., Ortega-Huerta, M.A., Townsend Peterson, A., Phillips, O.L., Williams, S.E. 2004. Extinction risk from climate change. Nature 427, 145–148. https://doi.org/10.1038/nature02121