Report on network problem formulations, targets and preferences, including guidance and data on targets and optimal TEN-N design criteria

The expansion of area-based conservation measures, such as protection and restoration efforts, as well as the design of multi-functional green and blue infrastructure, are widely seen as instrumental in halting or reversing further biodiversity decline. Europe has a long history of protection for biodiversity such as through the Natura 2000 program, however there still remain several gaps in sufficiently conserving the various aspects of biodiversity (e.g. species, ecosystems, functions & services) across Europe. Given the legal, political and societal challenges in negotiating the expansion of any new areas, it is key that these are done in strategic way and make use of best-available data to identify which areas would have the highest potential to contribute meaningfully to the conservation of biodiversity. Methods from systematic conservation planning (SCP) can be used to identify where such areas could be located under various assumptions and future narratives and can help to contribute to the design of a Trans-European Nature Network (TEN-N). In this report we 1) review previous SCP applications at various spatial and temporal grains across Europe and guiding principles for identifying conservation area expansions, 2) outline a methodology building on Favourable Reference Values (FRVs) to quantitatively identify the level of ambition for ensuring the long-term persistence of species of conservation priority, 3) describe a way to account for resilience towards future climates so as to ensure that protected areas play their role now and in the future, 4) describe how different parameters and datasets can be robustly integrated in a SCP problem formulation so as to identify where to best conserve, restore or manage European landscapes across different variants. By doing so this report provides a methodological basis on how to plan for a more coherent pan-European wide TEN-N. The TEN-N variants can inform on areas with high potential for local implementation, opportunities for cross-border conservation collaborations, or regions where future funding for conservation and restoration could be allocated across European member states. Furthermore, the TEN-N variants will be closely inspired by European policy targets and definitions and can thus serve as feasibility assessment of European Biodiversity policies under different scenarios.