The Bow-tie tool within the MARBEFES project is a structured risk and opportunity assessment methodology, adapted from ISO-accredited industry standards, to analyse causes, consequences, and management options for biodiversity change in marine and coastal systems. It combines conceptual clarity with stakeholder-driven inputs, enabling a visual representation of complex socio-ecological risks.

At its core, the Bow-tie diagram depicts a central “knot” representing a key biodiversity risk or management concern in a Broad Belt Transect (BBT). The left-hand side identifies drivers, activities, and pressures (causes), while the right-hand side details ecological and societal consequences. Preventive controls (e.g. policies, regulations, technical interventions) are linked to causes, while mitigation, compensation, adaptation, or recovery measures are linked to consequences. The diagram also allows for escalation factors, which highlight conditions undermining management effectiveness.

The framework integrates seamlessly with the DAPSI(W)R(M) approach (Drivers, Activities, Pressures, State changes, Impacts on Welfare, Responses with Measures), ensuring consistency with EU environmental directives such as the MSFD, MSPD, and the EU Biodiversity Strategy 2030. A major strength is its ability to highlight both risks and opportunities, allowing stakeholders to identify not only potential losses (e.g. habitat degradation, reduced fisheries yields) but also opportunities (e.g. new ecosystem services, innovative management approaches).

Within MARBEFES, Bow-tie diagrams are developed for each BBT through scenario and storyline workshops with local stakeholders. They serve as problem-structuring methods that can incorporate qualitative knowledge, semi-quantitative scoring, and potentially Bayesian Belief Network modelling. This approach has previously been tested in EU projects like CERES and VECTORS, where Bow-tie diagrams helped to visualise risks of climate change on fisheries and aquaculture.

The Bow-tie tool offers a clear, communicable picture of cumulative risks, enabling decision-makers, regulators, and practitioners to evaluate management strategies. It is particularly effective in transboundary contexts, where coherence across governance systems is critical. In MARBEFES, Bow-ties are applied to biodiversity-related challenges in multiple European case studies, helping to link natural capital, ecosystem services, and societal benefits into an integrated assessment.