Strategic placement of plantations enhances forest connectivity for birds in agricultural landscapes

Context: Land-use intensification in European agroecosystems has led to the loss and fragmentation of forested habitats, reducing their connectivity. Woody elements within the agricultural matrix play a crucial role in promoting functional connectivity among forest species. In agricultural landscapes, fast-growing plantations represent one such element that is expected to expand in the future due to current EU goals of climate change mitigation and energy security. Objectives: In this study, we aim to assess the potential contribution of poplar plantations in enhancing functional connectivity for forest birds in agricultural landscapes. Methods: To estimate functional connectivity, we conducted a scenario analysis in two agricultural sub-catchments located in Spain and France. Using a graph-based connectivity analysis and three focal forest bird species with different dispersal capacities, we estimated the added value of plantations under four scenarios where forests and plantation patches inside and outside Natura 2000 sites were added progressively. Results: We found that the contribution of plantations to functional connectivity is highly context-specific, depending largely on their spatial configuration and the arrangement of existing forest patches. Plantations were most effective when placed as stepping stones, for example, along river corridors connecting large, forested patches. Thus, simply increasing wooded areas through plantations does not necessarily yield a proportional improvement in connectivity. Conclusions: Expansion of poplar plantation areas and seminatural wooded patches in agroecosystems should explicitly consider the location of their implementation to effectively contribute to functional connectivity. Future policies could consider targeted incentives for the strategic placement of poplar plantations.