Ridge-to-reef conservation avoids future deforestation and sediment exposure of coral reefs

Land and sea are ecologically connected, and effective conservation of coastal ecosystems requires integrated planning that addresses threats spanning both realms. Deforestation in tropical catchments delivers sediment, nutrients, and other pollutants to downstream coral reefs, where these can impair coral physiology and alter reef community structure and resilience. Failing to address these cross-realm threats impacts ecosystem services vital to forest and coastal communities. A growing body of work has developed ridge-to-reef modelling approaches to link land-use change to downstream marine impacts. Yet, integrating these dynamics into spatial conservation planning remains challenging, particularly at large spatial scales and while accounting for socio-economic costs. Here, we compare alternative ridge-to-reef spatial planning strategies that integrate conservation actions on land and sea, showing that explicit representations of land–sea connectivity can substantially reduce future sediment exposure on reefs. Across the hyper-diverse Wallacea bioregion in Indonesia, we estimated sediment yields from terrestrial catchments for present and future deforestation scenarios. We then quantified and mapped how runoff affected downstream turbidity on reefs. Projected future sediment runoff to reefs varied widely, with the greatest impacts concentrated near large river catchments and deltas, especially in central-southeast Sulawesi. Joint land–sea conservation scenarios reduced reef sedimentation by 25% more than strategies that treated land and sea separately, with approaches that account for where sediment reaches reefs outperforming simpler proxies based on adjacency or distance. In the face of widespread deforestation and reef decline across the tropics, applying data-driven ridge-to-reef conservation approaches could provide major benefits for people and biodiversity.