Potential Impacts of Climate Interventions on Marine Ecosystems

Rising global temperatures pose significant risks to marine ecosystems, biodiversity, and fisheries. Recent comprehensive assessments suggest that large-scale mitigation efforts to limit warming are falling short, and all feasible future climate projections, including those that represent optimistic emissions reductions, exceed the Paris Agreement's 1.5°C or 2° warming targets during this century. While avoiding further CO2 emissions remains the most effective way to prevent environmental destabilization, interest is growing in climate interventions—deliberate, large-scale manipulations of the environment aimed at reducing global warming. These include carbon dioxide removal (CDR) to reduce atmospheric CO2 concentrations over time, and solar radiation modification (SRM), which reflects sunlight to lower surface temperatures but does not address root CO2 causes. The effects of these interventions on marine ecosystems, both direct and in combination with ongoing climate change, remain highly uncertain. Given the ocean's central role in regulating Earth's climate and supporting global food security, understanding these potential effects is crucial. This review provides an overview of proposed intervention methodologies for marine CDR and SRM and outlines the potential trade-offs and knowledge gaps associated with their impacts on marine ecosystems. Climate interventions have the potential to reduce warming-driven impacts, but could also alter marine food systems, biodiversity and ecosystem function. Effects will vary by pathway, scale, and regional context. Pathway-specific impact assessments are thus crucial to quantify trade-offs between plausible intervention scenarios as well as to identify their expected impacts on marine ecosystems in order to prioritize scaling efforts for low-risk pathways and avoid high-risk scenarios.

Plain Language Summary:
A rise in global temperatures from 1.5 to 2°C or above historical levels threatens marine life, ecosystems, biodiversity, and the sustainability of fisheries. Recent studies highlight that current efforts to keep warming within critical limits are insufficient, and even optimistic future climate scenarios predict that the 1.5°C threshold established by the Paris Agreement will be surpassed. In this context, climate intervention strategies are being explored as ways to potentially reduce the worsening effects of climate change and complement, not replace, decarbonization efforts. These strategies aim to either remove carbon dioxide from the atmosphere or reflect sunlight back into space to cool the Earth. While currently an understudied area of research, these methods could have profound impacts on the ocean, including changes to sea surface temperature and nutrient cycling, which in turn affect the abundance, distribution, and diversity of marine life as well as the human communities that rely on marine resources. This review synthesizes current research on the climate intervention strategies that are most likely to have direct impacts on the marine environment, emphasizing knowledge gaps as they relate to the potential impacts on marine ecosystems and the need for improved predictive models.