The Carbon–Water–Biodiversity Nexus: A Tri-Dimensional Review of Trade-Offs in Climate Mitigation Policies

Climate mitigation policies are essential for addressing the global challenge of anthropogenic climate change, but their implementation often entails complex interactions with water resources and biodiversity. This narrative review synthesizes recent peer-reviewed literature to explore the carbon–water–biodiversity nexus, emphasizing trade-offs and synergies in mitigation strategies. Traditional climate reviews have typically focused on single metrics, such as carbon emissions reduction, overlooking the interconnected dynamics among carbon sequestration, water security, and biodiversity conservation. By adopting a nexus-based approach, this review highlights how mitigation actions like afforestation, bioenergy with carbon capture and storage (BECCS), and renewable energy deployment can yield co-benefits, such as enhanced ecosystem services, while also posing risks like water scarcity and habitat loss. Drawing on studies from 2019 to 2025, we examine thematic areas including pairwise nexuses (carbon-water, carbon-biodiversity, water-biodiversity) and integrated tri-dimensional perspectives. Key findings reveal that while nature-based solutions offer substantial synergies, poorly designed policies can exacerbate trade-offs, particularly in water-stressed regions or biodiversity hotspots. The review underscores the need for holistic policy frameworks that incorporate nexus thinking to minimize adverse impacts and maximize sustainable outcomes. Objectives include providing a comprehensive synthesis of current evidence, identifying knowledge gaps, and proposing directions for future research to support equitable and effective climate action.