Priority research questions to generate decision‐grade data to enable coastal ecosystems to mitigate the climate and nutrient crises

1. Nature-Based Solutions, green-finance instruments and policies are now routinely constructed around carbon sequestration/storage (CSS) and nutrient bioremediation (NB). This integration builds on how Market-Based Instruments (e.g. payments-for-ecosystem-services) are regularly used in policies focused on terrestrial ecosystems. In marine and coastal systems poor understanding of CSS/NB biophysical processes and impacts of ecosystem quality/stressors, combined with methods and governance framework knowledge gaps, generate substantial uncertainty in outcomes. Reductions in output confidence preclude integration into Nature-Based Solutions, stifling market-based investment centred on conserving and restoring temperate coastal ecosystems.

2. To navigate this complex, rapidly evolving area, researchers from six continents engaged in a Priority Setting Exercise to generate 25 questions that, if answered within 10 years, will increase robustness, scalability and applicability of CSS/NB data across regions and ecosystems. We then used a modal analysis across five categories (time, geographic scale, technology complexity, cost and policy relevance) to expedite research-investment decisions.

3. Questions (numbers in brackets) were organised across six themes as follows: maps/quantitative evidence/long-term data (3), Processes/variability (6), Connectivity (2), Anthropogenic impacts (4), Methods/standards (6), Governance/conservation (4).

4. Questions under methods/standards and governance/trading schemes themes were generally identified to be the cheapest to answer and quickest to complete, whilst still having considerable geographic and policy relevance.

5. Policy implications: Identifying the enabling conditions for more efficient and successful approaches will greatly improve our understanding of ecosystem services. Together, these answers will then deliver the decision-grade data necessary to strengthen green-finance opportunities and address urgent climate and pollution (nutrient) crises.