Underpinning upscaling of nature-based solutions (NBS) in freshwaters using ecological principles and existing data

Global ambitions to restore degraded ecosystems, together with the recent adoption of the EU restoration law, demand an urgent and substantial upscaling of restoration efforts. Nature-based solutions (NBS) should play a key role in achieving targets and NBS were highlighted in a resolution from the Kunming-Montreal Biodiversity Framework as a mechanism to curb biodiversity declines and tackle the nature crisis. The widescale uptake of NBS offers enormous potential for improving biodiversity while addressing societal challenges in freshwater ecosystems, which are among the most degraded and increasingly threaten human wellbeing through droughts, floods and disease spread. The focus of this perspective is that the current use of NBS does not draw sufficiently on the large body of existing ecological knowledge and data, which limits the capacity of projects to deliver benefits to biodiversity, sustain ecosystem functioning, and build resilience. Ecological theory and related data on biodiversity-ecosystem functioning should underpin the next generation of freshwater NBS to ensure that our degraded ecosystems are recovered. One example is the metabolic theory of ecology (MTE) that could provide valuable insights into how biological systems, across levels of organization, respond to warming and should be incorporated into the next generation of freshwater NBS designs. In this perspective, we address some key science questions in relation to NBS that could be explored by using existing data, as well as the potential use of new sampling technologies in the context of NBS.