European forests are increasingly affected by natural disturbances, a new observational study shows. An international team of forestry scientists from Wageningen University & Research (WUR), the European Forest Institute (EFI) and 19 other research organizations from across Europe examined forest disturbances in Europe over the past 70 years and reported a statistically significant increasing trend in the article “Significant increase in natural disturbance impacts on European forests since 1950”, published in the scientific journal Global Change Biology.
Natural disturbances are part of forest ecosystems. By killing trees they change the environment, giving new, young trees room to grow. Dead trees are also important for biodiversity. However, the sharp increase in the number of disturbances in recent decades revealed in this study raises concerns about the disruption of the ecosystem services that our forests provide to society.
Increase and magnitude of disruption trends
“The analysis of the disturbance trends shows that damage from all disturbance causes – wind, fire, bark beetles and other pests – has clearly increased between 1950 and 2019,” said the lead author of the study Marco Patacca (WUR). The estimated average damage in Europe is 52,4 million cubic meters of wood per year between 1950 and 2019. However, if we look only at the last 20 years, this average has increased to around 80 million cubic meters per year, equivalent to 16% of the total annual timber harvest in the EU. At regional-national level, damaged timber sometimes exceeded 100% of the planned harvest, ultimately jeopardizing long-term forest management plans.
The major advantage of the methods used here for collecting measurement data from forest inventories is that they are very accurate and accurately reflect the cause of the disturbance. Satellites still cannot do this accurately.
Effects of forest disturbances
When forests are severely disturbed, extra CO2 is released instead of being stored. Furthermore, unplanned harvesting of damaged wood from these disturbances often leads to collapsing market prices and subsequently limits the future supply of wood for the European bioeconomy. Furthermore, habitat destruction and CO2 emissions could jeopardize the achievement of European climate and biodiversity targets.
Unique collection of data
The research team has compiled a unique collection of empirical observations of disturbance damage in Europe, consisting of more than 170.000 files. The data has been collected in the Database of Forest Disturbances in Europe (DFDE) and made public through the European research project I-Maestro. To overcome the scarcity of historical monitoring data, the team has set up a network of more than 20 national and European experts in this field. They collected country data on paper and in local languages and combined expert knowledge with statistical models to reconstruct the history of forest disturbances in 34 European countries.
Climate-driven disruptions
The researchers found that all causes of disturbance studied increased, but that bark beetles and other pests such as insects, diseases, fungi and other organisms showed the strongest increase. Because these causes are known to be highly sensitive to climate change, the group of scientists expects further and increasing damage as climate changes continue.
Need for pan-European monitoring
The analysis points to shortcomings in national reporting practices and highlights the urgent need to establish a pan-European, homogeneous monitoring system combining satellite and ground-based data on forest disturbances. Such a system would be crucial to understand and adapt to shifting disturbance regimes, assess policy trade-offs and design alternative forest management practices for all European forest areas. “To understand disturbance dynamics in forest ecosystems and their interactions with climate, data are critical,” Patacca said. “Unless we understand these dynamics, it will not be possible to design alternative, climate-smart management practices to adapt our forests to future changes in disturbance regimes.”
Source: Wageningen University & Research
