Green infrastructure and multifunctionality: enhancing ecological connectivity and complexity in mediterranean agricultural landscapes

The European Biodiversity Strategy for 2030 is triggering significant investments in Green Infrastructure (GI) for enhancing ecological connectivity, especially between the EU Natura2000 (N2K) sites scattered across highly anthropized landscapes. Also in response to this strategic target, EU environmental policies suggest restoring natural and semi-natural elements as crucial GI components across widespread agricultural matrices. Such restoration actions can improve the role of agroecosystems in supporting the N2K network, but little is known about actual GI deployment needs in different regions and for agricultural systems under different conditions. Traditional and extensive agricultural landscapes, characterized by diffuse naturalness, are actually multifunctional and able to support biodiversity, ecosystem resilience, and human well-being. By contrast, especially in SW Europe, there is an ongoing trend toward the homogenization and intensification of agricultural systems and a combined loss of associated landscape elements, such as natural and semi-natural linear elements (LE). These elements are among the landscape features to be increased in agricultural lands, since they could enhance biodiversity and connectivity acting in a complementary and synergic way with protected N2K sites. Within complex agroecosystems, LE themselves can be considered ecosystem subtypes, with their own structural and functional characteristics and varying condition. However, a comprehensive methodology is still needed to assess their capacity to support biodiversity and, on the other hand, there is little evidence on how to integrate LE condition assessments into GI plans and actions explicitly devoted to the improvement of N2K coherence (i.e., structural connectivity degree). This study was aimed at addressing the above-mentioned knowledge gaps by (i) identifying N2K-related GI deployment needs at a biogeographic level, with respect to the proportion of protected area and density of residual woody elements in arable lands of different Territorial Units (NUTS3), (ii) proposing a method for the assessment of LE condition, with an emphasis on the capacity to support plant species that are characteristic of local Potential Natural Vegetation (PNV) and pollinators, and (iii) developing and testing a fine-scale GI design for the improvement of N2K coherence, with conservation/restoration actions explicitly defined for LE. By means of a landscape ecology approach, strengthened by field and aerial vegetation surveys, the present research contributed the challenges posed by agriculture sustainability to be effectively addressed from a multilevel perspective. As a first result, four GI deployment needs were identified and spatialized in W Mediterranean Europe, with a prevalence of restoration of connections, followed by consolidation of node and link conservation, creation of additional protected areas, and enlargement of existing N2K sites. Second, a thorough LE condition assessment method was proposed and validated for 80 LE in Italy and Spain, resulting in good condition associated with contiguity to N2K sites and abundance of species characteristic of the local PNV. Third, in the peri-urban sector of the Metropolitan City of Rome, a local-level GI design process was developed to enhance the coherence between N2K patches. In this latter case, suggested GI actions for LE accounted for 0.0100% of the total agricultural area, with restoration intervention for barely 0.0073%. Despite small areas to be restored, the GI design was proved to almost double the original network coherence. Therefore the approach, suitable for biodiversity conservation under a land-sharing vision, ultimately confirmed the feasibility and potential replicability of restoration actions across different agricultural landscapes.