Right next to the city of Brussels lies the Sonian forest. It has a bio-diverse flora and fauna and covers about 5,000 ha. Described as 'Beech Cathedral', the Sonian Forest is known for its majestic beech trees (European beeches), which cover around 75% of the forest. A study commissioned by the Brussels environmental Minister, Celine Fremault, was conducted by the ULg, KUL, ULB, Brussels Environment and INRA to better understand the relationship between the trees and their changing environment. As we know, climate change affects all ecosystems on Earth, and the Sonian wood makes no exception.
Tree rings from 286 beech trees across Belgium were analyzed in order to compare the differences of growth and sensitivity between the Sonian and other regions. The researchers found that these trees are very sensitive to climate and are unable to adapt to increasing temperatures. Other factors linked to human activities, as well as the 'conservative' management during the 20th century, contributed to forest's vulnerability. By analyzing the tree rings, the study was able to observe the changes in growth rates during the last century. The years when the growth of beech trees was low, were also years of extreme weather (heat waves, droughts, storms etc).
These patterns of extreme weather is what climate change brings worldwide. The Intergovernmental Panel on Climate Change (IPCC) came out with disturbing predictions on Belgium's climate trends. We can expect to see an increase in annual temperature of the order of 2 °- 4 °. Annual precipitations will increase in the winter, but diminish in the summer. Even the optimistic IPCC models show that the temperate climate of Belgium will not be spared. We will see more severe thunderstorms and fludings as well as longer droughts and more frequent heat waves. The forecast for the 21st century does not promise a favorable climate for beech tree...
Faced with these changes, the researchers noted that a more dynamic forestry approach is required. The regeneration of old "beech cathedrals" that are coming to the end of their life cycle should be considered in the long term. Indeed, the beech trees that we would replant today will be mature only around 2115 ! By then we can be sure that Belgium will be experiencing unprecedented droughts and heatwaves for its temperate climate. The plan is to plant a series of other more tolerant species like the Sessile Oak and the small-leaved lime, that will mix with the beech trees or replace them. This will not only disperse the risks between the different species, but it will also allow them to benefit from positive interactions in their access to resources. The beech will not disappear from the Sonian Forest, but will be gradually confined to places that have the best conditions for them.
Studies like this allow us to better understand the long-term challenges and adapt our forestry strategies. Forests are very complex ecological systems and require very specific research. Temperate forests like the Sonian Forest do not react in the same way to climate change, as their Boreal or tropical counterparts. This research from Reading University's Department of Agriculture underlines that for example, if we only focus on the factor of the growth of trees in the case the boreal forest, we could misinterpret the results. A short-term temperature and increasing CO2 concentration could cause trees to grow faster, but on the long term, the trees will pull more nutrients, thus exhausting the soil. Despite their great importance, large-scale research in tropical forests is still very limited by lack of resources and logistical difficulties.
The study of the Sonian Forest reminds us that forests are delicate ecosystems and they react poorly to all the rapid changes linked to human activity. But what we also learned is that if we are capable of putting ecosystems at risk, we are also capable of helping them cope better with the changes and mitigate the consequences on their bio-diversities. All the world's forests are threatened, but we must understand that they are also our greatest ally against climate change. Good forest management can help maintain and increase their carbon storage potential thus improving their ability to mitigate climate change. Let's remember that we are all part of the same ecosystem. The future of forests and the future of human civilization are inseparable.
by Aleks Evtimov