Authors: Jo Van Brusselen (EFI), Yasmin Maximo (EFI), Bernhard Wolfslehner (EFI)
Forests cover more than 40% of Europe’s land, and can be classified into 76 distinct forest types. This demonstrates the significant differences in tree species and related biodiversity across the region (EEA, 2006). Forests play important roles in society, storing carbon, providing wood and non-wood products, serving as recreational, spiritual, and protective sites, and hosting an abundance of biodiversity (FAO, 2000). To keep, manage and protect forests in a way that balances all these different expectations, it is of utmost importance to know more about them.
The need for timely and accurate data about forests is not new. The oldest National Forest Inventories (NFIs) were established just over a century ago in Norway, Finland and then Sweden (Breidenbach et al., 2021). Forest monitoring has been constantly evolving through time, in tune with new scientific methods and with evolving societal expectations towards forests. It has therefore evolved from a tool for systematically monitoring industrial wood resources, towards also covering other ecosystem services in the context of biodiversity protection or of climate change.
National Forest Inventories (NFIs), have evolved in many countries from stand-based almost log-book based inventories and/or systematic plot-based in-situ observations in the forests, to multi-source inventories. The latter integrate many different data sources including Earth Observation data (from a variety of sensors, including air- and space-borne optical, near-infrared, radar and lidar* data). For many indicators, remote sensing1 and in-situ monitoring (on site) are complementary and mutually reinforcing. This data integration leads to the delivery of data and maps with higher spatial and temporal resolutions (i.e. with more spatial detail, and more observations within a given time period). In-situ data collected in the forest itself guarantees “ground truthing”, which remote sensing uses for calibration and validation of models that link the radiometric signal as observed by the satellite, with the variable that was measured in the forest.
Since 1947, countries have been reporting forest data using increasingly harmonized definitions, driven through cooperation on the Global Forest Resources Assessments (G-FRA) led by the Food and Agriculture Organisation (FAO). At pan-European level, the Forest Europe ministerial process developed a set of criteria and indicators (C&I), consisting of 6 criteria and 35 quantitative indicators (describing the forest status and changes) and additional qualitative indicators. These have been used for the 5-yearly State of Europe’s Forests reports since 2002.
Assessing the status of Sustainable Forest Management requires still more attention both on pan-European and on national levels (Linser et al., 2022) as related targets or thresholds are not yet agreed. Discussions on revising the indicator set as emphasised in Forest Europe’s Bonn Ministerial Declaration (2024) are underway. A revised set will have to reflect more comprehensive monitoring needs for the transition towards a circular bioeconomy.
To follow-up on the implementation of the EU Forest Strategy for 2030, several issues cannot be monitored sufficiently yet with the pan-European indicator set at the European level (Lier et al., 2022). For instance, the European Union has increased the demand for forest data with legislation such as the LULUCF regulation, the REDII/REDIII directive/s, the sustainable finance regulation, the nature restoration law and the regulation on deforestation free-products. These acts reinforced the need at EU and national levels to generate high-quality data to allow for proof of compliance, monitoring and enforcement. ‘High quality data’ means data which is comparable across the Union, with sufficiently high spatial and temporal resolution, and which completes currently existing data gaps. The evaluation of some policy targets cannot be done appropriately at this moment with the existing systems. For example, NFI data are collected on average only every 5 years, while for some indicators, policy evaluation would legally require yearly data (Neumann et al., 2022). Other examples concern the monitoring of socio-economic indicators concerning the development of wood-based innovations in the bioeconomy, or the measurement of the uptake of climate-friendly products (Hassegawa et al., 2021).
Comprehensive monitoring may also have to consider those who rely on and work with forests. The motives and behaviour of forest owners and managers across the EU need to be better understood to help decision makers facilitate the transition to more resilient climate adaptive forests and their sustainable use. Consideration could even be extended to forest industries’ innovation and competitive capability, and the public as forest beneficiaries, who through their expectations and beliefs influence the use and consumption of the forest. European forest monitoring therefore needs to be holistic, addressing multi-sectoral, multi-user information needs.
Additional efforts to harmonise data and to make data comparable, while not having been collected according to the same methodology, are still necessary – even if a lot was achieved in the past two decades, e.g. through the European Network of National Forest Inventories (ENFIN) and projects such as Diabolo. Standardisation - meaning enforcing the same methodology for all data collection and requiring changes from previously established methods and definitions - is often considered difficult, for practical and legal reasons, by existing national data collection institutions. Any initiative to harmonize or standardise the data should consider compatibility also with international and national definitions and ensure data continuity.
Finally, monitoring capability is moving from observing the ‘state’ of the forests, towards benchmarking and predicting the future of European forests and their capacity to deliver various ecosystem services to society. This relies on scenario-based modelling, allowing the better prediction of the impacts of climate and management decisions and consumer choices on the future delivery of forest ecosystem services.
*Lidar stands for "Light Detection and Ranging" - it is a remote sensing technology that uses laser light to measure distances between the sensor and the point or object of interest. When measuring a multitude of points, 3D models can be created, e.g. of the forest canopy. The higher the number of points that are measured per square meter, the better the 3D model will be. The Lidar data can be used as inputs to modelling forest structure, tree species composition, and when assessed over a time period, it can serve as an input to measuring forest growth.
1Remote sensing means a forest area is monitored by measuring the reflected and emitted radiation from a distance. This is very often done by satellite, or by purpose-specific aeroplanes, drones etc.
References
FAO. 2020. Global Forest Resources Assessment 2020: Main report. Food and Agricultural Organization of the United Nations, Rome. https://doi.org/10.4060/ca9825en
Breidenbach, J.; McRoberts, R.E.; Alberdi, I.; Antón-Fernández, C. & Tomppo, E. (2021). A century of national forest inventories – informing past, present and future decisions. Forest Ecosystems, 8. https://doi.org/10.1186/s40663-021-00315-x
EEA, 2006. European forest types – Categories and types for sustainable forest management reporting and policy. EEA Technical report No. 9/2006. European Environment Agency, Copenhagen. URL: https://www.eea.europa.eu/publications/technical_report_2006_9
Hassegawa, M.; Van Brusselen, J.; Cramm, M.; Verkerk, P.J. Wood-Based Products in the Circular Bioeconomy: Status and Opportunities towards Environmental Sustainability. Land 2022, 11, 2131. https://doi.org/10.3390/land11122131
Lier, M.; Köhl, M.; Korhonen, K.T.; Linser, S.; Prins, K.; Talarczyk, A. The New EU Forest Strategy for 2030: A New Understanding of Sustainable Forest Management? Forests 2022, 13, 245. https://doi.org/10.3390/f13020245
Linser, S. & Wolfslehner, B. (2022). National Implementation of the Forest Europe Indicators for Sustainable Forest Management. Forests. https://www.mdpi.com/1999-4907/13/2/191
Neumann, T., Karin Attström, Francesca Finello, Amy Donnelly, Jo Van Brusselen, Bernhard Wolfslehner, Evgenia Gordeeva, Jeanne-Lazya Roux, Päivi Pelli, Yasmin Imparato Maximo, Gherardo Chirici, Costanza Borghi, Saverio Francini (2022). Support For The Impact Assessment Of The Legislative Proposal For A New Eu Framework On Forest Monitoring And Strategic Plans. Final Report. European Commission, Brussels. 480pp. URL: https://environment.ec.europa.eu/system/files/2023-11/Report%20-%20support%20for%20the%20Impact%20Assessment%20of%20the%20proposal.pdf