Building evidence for action: Novel assessment of ocean acidification impacts around the UK

Background: The ocean naturally absorbs CO2 from the atmosphere; CO2 reacts with water forming a weak acid before rapidly dissociating as part of the marine carbonate system. This carbonate system buffers changes in acidity (or pH) over geological timescales through calcium carbonate weathering. However, the rate of atmospheric CO2 emissions, and subsequent oceanic uptake, has increased dramatically as a result of anthropogenic activities, resulting in "ocean acidification" (OA). OA is a change in the carbonate system including a decrease in pH. Under future 'worst-case' emissions scenarios the oceans are projected to become 150% more acidic on a global scale. OA has wide-ranging consequences for marine organisms, ecosystems and ecosystem services, mostly resulting in detrimental impacts. For example, shellfish aquaculture facilities on the west coast of the USA already experience losses in oyster larvae as a result of lower pH water; pteropods, free-swimming snails that are important food for fish such as salmon, are already found with dissolving shells in some regions of lower pH water. These impacts are just examples of how environmental change is, and will continue to, affect society and the economy. Recent evidence (OSPAR, QSR2023 in prep.) shows that coastal waters around the UK have been experiencing rapid rates of acidification, with high levels of seasonal variability. This new data and modelling analysis forecasts areas of UK coastal waters to continue to acidify, with periods of extreme conditions expected by the 2030s, that could cause acute stress response in some important UK species.

Through its research programmes and engagement with the United Nations Framework Convention on Climate Change, the Global Ocean Acidification Observing Network (GOA-ON), the North East Atlantic regional GOA-ON Hub, and the International Alliance to Combat Ocean Acidification (OA Alliance), the UK government, through DEFRA, has been considering how to move forward with OA research and action. The OA Alliance calls for action, recognising that states, institutions or communities, should produce and deliver on an OA Action Plan. These plans provide recommendations for action based around five goals: 1. Advance scientific understanding; 2. Reduce the causes of ocean acidification; 3. Build adaptation and resilience; 4. Expand public awareness; and 5. Build sustained international support. The OA Alliance also provide guidance on how plans can be used to support political frameworks and deliver on high-level goals, such as the UN Sustainable Development Goals, OSPAR convention, and the World Meteorological Organisation Climate Indicators. However regional and local consideration of vulnerabilities are needed in order to decide the best course of action, including providing evidence about the risks to species, potential adaptation responses, as well as considering barriers to OA adaptation strategies.

Aims: This project aims to develop a novel spatially resolved assessment of OA impacts to UK species, habitats and ecosystem services, building evidence that can be used to inform action relating to OA impacts and adaptation in the UK.

Approach: The research will be focussed around three objectives: 1. Review the current status of the UK marine environment in relation to OA and assess the vulnerability of key habitats and biota; 2. Make projections of future risk to ecosystems and ecosystem services; 3. Understand stakeholder vulnerabilities, potential adaptation strategies and any potential barriers to action, and assess the potential impact of action on reducing the risk to OA around the UK. The research will directly inform Defra's evidence team and contribute to future policies and management plans.