Europe’s beech forests threatened by climate change

A new study finds that climate change could significantly reduce beech trees’ growth across most of the continent this century. Forest dieback may follow, the researchers warn.

Beech forests in Europe have far-reaching benefits. Like many other forests, they provide important habitat for wildlife and contribute to the water and carbon cycle. Beech forests are also economically important as a source of timber and are socially valued as spaces for recreation.

This new pan-European study predicts that climate change will reduce these benefits by restricting the growth of beech trees (Fagus sylvatica L.) in most European countries. Previous studies have shown the effects of climate change on beech trees, but only at a regional level. The study provides a large-scale analysis, encompassing the full range of the species in Europe.

The researchers began by building a comprehensive picture of which climatic or geographic factors affect beech growth, focusing on 21 possible influences. They related these factors to the width of 780 000 tree rings, taken from 5800 trees at 324 sites across Europe, and which grew during two periods: 1955–1985 and 1986–2016.

Temperatures increased by 1°C in many European regions between these two 31-year periods. In fact, 1986–2016 was the warmest 31-year period in Europe in the past 500 years.

Of the 21 factors considered, reduced rainfall and higher temperatures significantly limited tree growth during these periods, as shown by narrower tree rings. This was especially true when these two factors occurred at the same time, during so-called ‘hot droughts’.

The data revealed that climate change has already affected tree growth in Europe. Beech tree growth fell by up to 20% in southern Europe during 1986–2016, compared with 1955–1985. Northern areas were not affected in the same way, however. Growth increased by 20% in Norway and Sweden, for instance.

The researchers used the new data to predict likely growth rates under two future climate change scenarios, up to the year 2090. They based their climate change scenarios on shared socioeconomic pathways (SSPs), which examine how society, demographics and economics might develop over the next century¹.

The first scenario, SSP1–2.6, is the more optimistic of the two. It assumes that greenhouse gas (GHG) emissions will reach net zero by 2050, with global average temperatures rising by nearly 2°C by the end of this century, compared with 1900.

Under these conditions, beech tree growth would drop by up to 30% in southern Europe between 2020 and 2050, compared with the 1986–2016 period, the study predicts. On the other hand, growth increases of up to 25% would be predicted for mountainous areas of central Europe, and around 35% in southern Scandinavia. This pattern would continue up to 2090, with declines becoming even more pronounced in southern Europe.

The second scenario, SSP-8.5, is more pessimistic, but not unrealistic.  It assumes very high GHG emissions and average temperature rises of around 4.5°C by 2100. Hotter droughts are expected to be common.

Under these conditions, beech tree growth would decline sharply in much of Europe, by as much as 20–30% in most central European forests during 2020–2050, the study predicts. In southern Europe, losses would be over 50%, particularly during 2040–2070. Growth would continue to increase in northern (north of 55°N) and mountainous regions up to 2090, but these areas represent only a small part of the trees’ range and a small proportion of trees.

Separate research has reported that declining growth is a precursor of dieback. Thus, as well as reducing the value of Europe’s beech forests, these losses could also signal the death of vast areas of forest. The most vulnerable sites are at the southern edge of the species’ range, in Mediterranean countries, the study indicates. The researchers conclude that immediate action is needed to adapt forests to climate change and to develop sustainable management strategies, and that forest managers should consider the study’s results in long-term silviculture plans².

Further Information

According to the study’s models, beech would improve its overall performance at high altitudes and latitudes if the climate models are fulfilled and seasonal temperatures increase. This may make beech more competitive compared to other species adapted to colder climates that may suffer from rising temperatures such as spruce or birch, and therefore it could become a dominant species in these areas. However, if the temperature increase is too steep (as in the SSP5 scenario), the increase in growth is more limited to northern latitudes. Nevertheless, the researchers say that more research is needed to focus on the other tree species or on inter-species competition to provide a more accurate answer to this question.

Footnotes:

1. Shared socioeconomic pathways are being used as inputs for the latest climate models within the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report. For details of IPCC’s climate change scenarios and associated temperature rises, see: Climate Change 2021: The Physical Science Basis (IPCC, 2021).
2. Despite uncertainty on the magnitude of ecological and economic damages as a result of the latest severe European droughts, the debate on modifying European forests has already begun. In terms of immediate action, the information could be used, for example, for planning the timing of cutting actions or as a hint for assisted migration. The researchers say that robust scientific guidance is needed more than ever to set future paths for sustainable forest management.

Source:

Martinez del Castillo, E., Zang, C.S., Buras, A. et al. (2022) Climate-change-driven growth decline of European beech forests. Communications Biology 5: 163. Available from: Climate-change-driven growth decline of European beech forests | Communications Biology (nature.com)

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“Science for Environment Policy”: European Commission DG Environment News Alert Service, edited by the Science Communication Unit, The University of the West of England, Bristol.

Notes on content:

The contents and views included in Science for Environment Policy are based on independent, peer reviewed research and do not necessarily reflect the position of the European Commission. Please note that this article is a summary of only one study. Other studies may come to other conclusions.