A research team from, Johannes Gutenberg University Mainz (JGU), has discovered a drastic growth decline in Europe’s beech forests over recent decades.
What are the benefits of beech forests?
Beech forests are crucial stores of carbon dioxide. The models developed by scientists are based on tree ring analyses from all over Europe, utilising well-established climate scenarios.
Beech is one of the most important trees in the forests of Europe. This is because beech forests are both economically important and ecologically high in value. Almost 100 beech forest regions in 18 European countries are listed as UNESCO World Heritage Sites.
However, climate change could place severe pressure on stocks in the future, both in geographical and ecological terms. Evidence of this has already been published in regional studies, but to date no comprehensive analysis has been conducted.
How did scientists gather this data?
Edurne Martinez del Castillo, a member of Professor Jan Esper’s Climatology Group at Mainz University, has now investigated this development for the species Fagus sylvatica, in collaboration with partners from 32 scientific institutions.
Over 780,000 tree ring measurements were performed on 5,800 trees at 324 sites across Europe, from the North of Scotland to mainland Greece. This data allowed researchers to analyse the growth rates of the trees over the past six decades, and to forecast likely trends in the future.
What has this study revealed regarding Europe’s beech forests?
Beech forests in Europe are severely threatened by climate change, particularly in Southern European countries, but also in central Europe. Models project severe beech growth declines over the next 70 years – ranging from 20% to perhaps more than 50%, depending on the climate change scenario and the region under examination.
“We expect high productivity declines due to increased drought severity, especially at the southern limits of the beech’s distribution range,” explained Dr Edurne Martinez del Castillo from JGU.
Researchers have stressed that this will seriously impact the environment as well as the forestry, and states that imminent measures are required to adapt Europe’s beech forests.
The results reveal marked geographical differences between the two study periods of 1955 to 1985 and 1986 to 2016. For example, the model tree growth rate over the past six decades was two to three times higher in low-lying areas of North-Western and central Europe – such as coastal regions in Belgium, the Netherlands, Denmark, and the British Isles – than towards the Southern distribution limits.
By comparing the two 31-year periods, a remarkable decline in beech tree growth was revealed, in almost all distribution regions. The models portrayed a strong contrast between Northern Europe with Sweden and Norway, where growth has risen by 20%, and Southern Europe, where growth has declined by as much as 20%.
What does this reveal regarding future forecasts?
Based on two widely accepted climate research scenarios from the Coupled Model Intercomparison Project (CMIP), Edurne Martinez del Castillo has projected the developments likely to occur over the next 70 years through to 2090.
“Even assuming a relatively optimistic climate change scenario, we will see sharp growth reductions of up to 30% in southern Europe between 2020 and 2050 compared to the 1986 to 2016 period,” observed Castillo.
The optimistic climate model assumes a temperature increase of 1°C by 2090, while the pessimistic scenario predicts a warming of 5°C. The latter would have dramatic consequences. Beech productivity would decline sharply in much of Europe, by as much as 20% to 30% in most central European forests.
“In southern Europe, losses could even exceed 50%,” concluded Castillo, noting that increased aridity would affect the pattern. In contrast, in the North and in mountainous regions, the growth trend would be positive. Overall, however, the gains will not be as severe as the losses, neither geographically nor in terms of absolute numbers.
In light of these forecasts, the authors of the study believe that forest adaptation measures are urgently required to mitigate serious environmental and economic consequences. This is because beech forests act as carbon dioxide sinks, and the reduction in tree growth is expected to lead to further forest dieback, reducing this impact.
This study was funded by the Alexander von Humboldt Foundation and has now been published in Communications Biology.
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