Wildlife monitoring efforts have a way to go before we understand the biodiversity of Europe’s forests

To design and enact successful conservation policies, we need sufficient wildlife data. Forest ecosystems, whether managed for nature or as bio-economies, urgently require more and better wildlife records, especially as nature faces additional pressures from climate change. Long-term wildlife monitoring programmes exist, but they tend to be biased in their focus and are often inadequate in providing a full picture – and monitoring of biodiversity in forests more specifically remains scattered and inconsistent.

Now, a Europe-wide team of researchers has created a database of existing records to estimate how much more sampling must be done to sufficiently understand species richness and composition in Europe’s forests – valuable to guide decision-making. The researchers examined six forest types (hemiboreal, alpine, acidophilus oak, mesophytic deciduous, lowland beech and mountainous beech) and six species groups (vascular plants, bryophytes, lichens, fungi, birds and beetles) across 2,000 European locations.

Using this database, the researchers calculated the extra sampling effort needed to reliably estimate biodiversity health in Europe’s forests. Their results show that birds, lichens and bryophytes require the least additional sampling effort, likely due to the higher level of existing data. Other groups need greater effort, especially saproxylic beetles, vascular plants and fungi. 

While birds might need 2 to 17 plots monitored per forest site to assess species richness, depending on the site and forest category, fungi might need anything from 7 to 147 based on the same criteria. While the number of plots needing sampling for species richness was always higher than those derived from the researchers’ reference database, sampling for species composition at the site scale tended not to require much higher effort, except for saproxylic beetles, which were under-sampled in all forest categories.

Coordinated efforts to monitor forest biodiversity have been strongly limited, they noted, and considerable investment is needed. To achieve a minimum valid level of knowledge,  sampling needs to increase in scale to something similar to the continent’s largest forest monitoring programme, ICP Forests, which covers 6,000 plots to study the impact of air pollution. 

For comparison, to reach a 90% sampling completeness for species richness in EU forests the study estimates a need for 3–147 plots per site across 3–39 sites per forest type; to achieve accurate knowledge of species composition across all six taxonomic groups and forest types, it estimates a total need of 5–25 plots per site at 5–20 sites per forest. The authors note that while this may seem insufficient to detect biodiversity changes at local or regional level, it is enough to detect broad-scale changes happening at a continental level. 

As things stand, a renewed focus on forest biodiversity could be hindered by a lack of knowledge. Also, current forest sampling efforts under the Habitats Directive vary greatly by country, with complete lists of plant species being rare, and monitoring of animals rarer still. 

The study offers ideas on how to better monitor biodiversity, potentially providing direct input to European policies should there be a move towards intensive mandatory monitoring. Currently, efforts to improve knowledge of biodiversity in Europe fall under the broader EU biodiversity strategy for 2030. Crucially, the findings also provide a moveable point of reference: the researchers note the importance of periodically reassessing sampling completeness as more data are collected for the taxonomic groups, making revisions until the optimum sampling effort – still a way off – has been achieved to support policymaking.

Reference: 

Burrascano, S., Chojnacki, L., Balducci, L., Chianucci, F., Haeler, E., Kepfer-Rojas, S., Paillet, Y., de Andrade, R.B., Boch, S., De Smedt, P. and Fischer, M., 2025. Towards an effective in-situ biodiversity assessment in European forests. Basic and Applied Ecology, 84, pp.121-132. www.sciencedirect.com/science/article/pii/S1439179125000246

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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.