Working Group on Biodiversity Science (WGBIODIV; outputs from 2024 meeting)

We set out to provide a multifaceted perspective of biodiversity change across the Northeast Atlantic, identify areas where biodiversity is particularly at risk given abrupt or gradual responses of marine biota, and examine the efficacy of spatial protection measures to conserve and protect nature. We used a suite of structural and functional metrics across plankton, benthos and fish assemblages, and considered various climate change, fisheries management and marine artificial structure scenarios. Our work either directly informed Indicator Assessments for the OSPAR Quality Status Report 2023 or could be applied to inform ecosystem-based management. This contribution is not ICES advice but the work of a science working group (WGBIODIV). Across the various biodiversity metrics, the abundances, distribution and productivity of key groups representing different trophic levels were in flux in many of the areas assessed. We provide a contribution on how benthic effect trait composition determines seabed ecosystem functions, how these vary along environmental gradients but are similarly vulnerable to bottom trawling. Many of the observed changes in plankton and predicted changes in fish species distributions and foodweb properties were affected by climate change. For instance, most plankton lifeforms, which include groups of phytoplankton, zooplankton, and ichthyoplankton, have been declining in abundance throughout the Northeast Atlantic in the long term and these changes were associated either directly or indirectly with environmental change linked to climate change. The distribution of species richness across the fish component of the foodweb is also projected to be affected by climate change with spatially extensive increases in species richness largely driven by the expansion in range of smaller piscivores with relatively low predator–prey mass ratios by 2095 under RCP 4.5. Based on projections from ecosystem models, we provide how proactive, regionalized Nature-Based Solutions could ensure resilience and attain Good Environmental Status in future, contributing to the recovery of both the ecological integrity and the socio-economic benefits of marine ecosystems. Finally, using a global meta-analysis, we find that decommissioning options aimed at repurposing marine energy infrastructure into artificial reefs may not provide the intended benefits. Despite the wealth of evidence of biodiversity change presented here, we highlight the need to develop international consensus on how to operationalize effective biodiversity targets where thresholds and tipping points are insufficient to ‘bend the curve’ towards nature recovery.