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WILDCARD

Horizon Europe Project: Effects of reWILDing on forests and agricultural lands on CARbon sequestration and Diversity (WILDCARD)

Logo WILDCARD

How can set-aside forests contribute to climate change mitigation and the conservation of biodiversity? This is the central question that WILCDARD, the Horizon Europe Project, in which FVA plays a decisive role, strives to answer since its start in January 2024.

Overview

All over Europe, nature is making a comeback. As more people move to cities and other land-use changes occur, the EU’s forest area is increasing, having grown by almost 10 % (+14 million hectares) between 1990 and 2020. On top of that, 10-29 million hectares of agricultural land are likely to be abandoned between 2000 and 2030. This leaves potential for native flora, fauna and complex ecosystems to reclaim space, bringing natural ‘rewilding’ to the centre of Europe’s environmental policy discussions.

Understanding how rewilding can contribute to solving the climate and biodiversity crises is crucial for the successful implementation of the EU Biodiversity Strategy, the EU Nature Restoration Law, and the EU Green Deal - a mission to be tackled by the new Horizon Europe project, WILDCARD. Starting in January 2024, the project is, for the first time, systematically assessing the impacts of two major rewilding approaches on carbon sequestration and biodiversity conservation at the European scale. Currently, a lack of comprehensive research on the topic prevents rewilding from being fully integrated into Europe’s strategy to reach net zero carbon emissions by 2050.

Running until 2027 with an EU budget of € 8,9 million and a Swiss contribution of € 1,2 million, WILDCARD combines field observations, remote sensing (e.g. LiDAR data) and computer simulations of shifts in vegetation cover with economic, societal, and political analyses. The goal is to identify hotspots of rewilding in future climate and land use scenarios, as well as their overall impact at multiple time scales. WILDCARD mainly focuses on two aspects of rewilding: proforestation (halting forest management to allow for spontaneous forest development) and natural rewilding following agricultural land abandonment. Both are low-cost approaches that let nature do the job of restoring ecosystems.

With an interdisciplinary approach and cross-country collaboration between 16 partners, the project will investigate regulatory, cultural and economic barriers to rewilding, while also identifying social innovation mechanisms, models and incentives to foster its adoption and social acceptability. The research will not be limited to the bright side of rewilding but also seek to identify trade-offs, such as the possibility of increased forest fires due to the abandonment of forest management in dry regions of Europe. Locations with the highest rewilding potential and relatively small trade-offs will be prioritised for policy recommendations.

Role of FVA in WILDCARD

The FVA plays a key role in the work package  ‘proforestation’. In addition to coordinating this package, the impacts of setting aside forests on above-ground biodiversity, and the development of biodiversity indicators based on forest structures using USV LiDAR (ULS) are being investigated.

Lead and coordination of the workpackage "proforestation"

The FVA is leading the work package that investigates the European potential for above- and below-ground carbon sequestration and storage as well as changes in biodiversity in set-aside forests and primary forests (proforestation). To this end, it draws on a broad database covering the European climate gradient from the Mediterranean to the boreal zone. The dendrometric data from over 700 study areas and over 40 European institutions are organized by the FVA, and harmonized and stored in a unique database by a partner institution, VUK (Czech Republic). This data, together with other biodiversity data (from around 300 plots), forms the basis for the analysis. Important parameters are the progressive duration of setting aside and the accompanying changes over time. The remaining European primeval forests are used as a natural reference. 

The managed forests are regarded as the normal state (baseline) in the study structure.

Based on this data, models are created to quantify and predict the long-term development of biodiversity and carbon stocks on set-aside areas.

Implication of proforestation on biodiversity

A central question within WILDCARD is how aboveground biodiversity develops in forests following management cessation. FVA plays a leading role in the statistical analyses aiming to answer this question, and in gathering and harmonizing the multi-taxon biodiversity data required for these analyses. This encompasses not only biodiversity data collected by FVA in forest reserves of the state of Baden-Württemberg (see FVA-Project "Biodiversität entlang eines Bewirtschaftungsgradienten" for more details), but also data from forest reserves all across Europe, contributed by other WILDCARD members and a multitude of external partners (largely part of the European Forest Reserves Initiative, EuFoRIa).

Previous research comparing biodiversity in managed and unmanaged forests has mainly focused on overall species richness and diversity as metrics of biodiversity. However, as set-aside forests advance towards later successional stages, not all species will necessarily profit from these changes. Thus, the conservation value of forest set-asides may be better represented by the response of species, guilds and functional traits that are intimately linked to late-successional forests (e.g. Figure 1A-B) and the associated structures (e.g. large trees, rich in microhabitats, e.g. Figure 1C). Responses to time since abandonment can also be expected to be complex and non-linear, and it remains unclear how long after abandonment gap dynamics set in, creating habitat for gap-associated species (e.g. Figure 1D) within late-successional stands.

Example species dependent on different forest successional stages.

Fig. 1: Example species dependent on different forest successional stages.

A. Late succession: Eurasian three-toed woodpecker (Picoides tridactylus), critically endangered in Baden-Württemberg
B. Late succession: Blue ground beetle (Carabus intricatus), vulnerable in both Germany and Baden-Württemberg
C. Late succession: Old pedunculate oak (Quercus robur)
D. Early succession: Greater butterfly-orchid (Platanthera clorantha), vulnerable in Germany and near-threatened in Baden-Württemberg

(Photos A, C and D by João M. Cordeiro Pereira, B by Sebastian Schwegmann)

Therefore, the goals of our analysis are to:

  1. assess the effect of time since abandonment on the composition and functional trait makeup of communities, across a broad range of organism groups (vascular plants, bryophytes, lichens, fungi, insects, birds and bats)
  2. identify aspects of forest structure and composition that serve as reliable indicators for the occurrence of old-growth specialists, red-listed species and functional diversity
  3. disentangle the links between time since abandonment, forest structure and biodiversity, providing insight into the ecological mechanisms driving biodiversity responses
  4. compare the development of forest structure and biodiversity in set-asides to that of baseline stands (managed forests) and reference stands (primary forests).

The statistical approaches used will be: Generalized Additive Models (GAM), that account for non-linear relationships; Hierarchical Modelling of Species Communities (HMSC), which allows for modelling community composition, including functional traits, as a function of environmental variables; and Structural Equation Models (SEM), that test causal links between time since abandonment, forest structure and biodiversity. Data on forest structure and composition will be derived from dendrometric inventories (gathered and harmonized by VUK) and LiDAR surveys (organized by FVA alongside VUK, see section below) on the same sites where biodiversity data has been collected.

Diagram representing the linkages that FVA will test between time since abandonment (management cessation) and aboveground biodiversity.

Fig. 2: Diagram representing the linkages that FVA will test between time since abandonment (management cessation) and aboveground biodiversity.

This work is closely coordinated with other WILDCARD partners analysing the effects of management cessation on belowground biodiversity (at EVINBO (Belgium) and ETH Zurich (Switzerland)), aboveground carbon storage (at NW-FVA (Germany)) and building dynamic models for the future development of forest structure and biodiversity (at ETH Zurich).

Remote sensing

The study of biodiversity indicators of forest structures is supported by remote sensing methods using drone-based LiDAR (ULS). LiDAR (Light Detection and Ranging) is an active system that can measure the distances of objects very precisely. A laser scanner emits laser pulses, which are reflected by objects. By measuring the time the laser pulse takes from emission to detection by the sensor, distances can be determined very precisely and detailed 3D models of the forest can be calculated. An example of such a 3D model, which was combined with the colouring from a camera, is shown in Figure 3.

Cross section through a point cloud of a forest based on a ULS flight.

Fig. 3: Cross section through a point cloud of a forest based on a ULS flight.

The FVA is involved in the project in both data collection and data analysis. The carrier system is a DJI Matrice 300 RTK (Figure 4, left) which, thanks to the RTK system, enables a high positioning accuracy of a few centimetres. The sensors used are the Zenmuse L1 (Figure 4, right) and the Zenmuse L2, both from DJI. In order to be able to record forest structures even at ground level, it is essential to collect data during the leaf-free period. For this reason, the FVA began the first flight campaigns at the end of November 2024 and completed them at the end of March 2025. Further flight campaigns are planned for the winter of 2025/26.

Fig. 4: Drone system used (DJI M300 RTK, left) and laser scanner (DJI Zenmuse L1, right) (Photos:  Philipp Eisnecker)

The fifteen study areas flown over by the FVA are protected forests and are located almost exclusively within FFH bird protection areas or nature reserves and are subject to restrictions regarding drone activity. Therefore, it was necessary to obtain a nature conservation permit. The locations of the study areas are shown in the map (Figure 5).

Overview map of the study areas surveyed by the FVA.

Fig. 5: Overview map of the study areas surveyed by the FVA.

A core area of 1 ha was flown over each study area, in which additional data such as soil carbon and biodiversity were collected from the ground. The core area was then expanded to a target of 30 ha, depending on local availability. The flight result was to be at least 1000 points/m², and parameters such as flight speed, altitude, and overlap area had to be adjusted accordingly.

After data collection, the point clouds from all study areas in the project will be forwarded to the project partner VUK, which will calculate structural indices using automated and standardized procedures. These calculated indices will then be fed back to the FVA, whose task it is to analyse the possibility of upscaling the structural information to a larger area. For this purpose, the products used in the project, MoBiTools, based on aerial photographs, calculated for the entire state of Baden-Württemberg and models were created that describe the relationship between these products and the indices.

Funding

The project is funded by the European Union program "Horizon Europe" with the number 101081177.

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