Generating affordable protection of high seas biodiversity through cross-sectoral spatial planning

Over the past 20 years, industrial activities have accelerated in the open ocean. Fishing, shipping, and deep-sea mining are major drivers of this "blue acceleration,"with each having its own suite of impacts on species, communities, and ecosystems. We use a systematic conservation planning approach combining ecological and socioeconomic data from the fishing, shipping, and deep-sea mining sectors to examine the utility of a cross-sectoral approach. Applying our framework to the Indian Ocean, we show that the cross-sectoral spatial plan meets the same conservation targets at a lower overall cost and using a smaller area compared with sectorspecific plans implemented simultaneously. In addition, we identify areas that are best suited to conservation using a replacement cost metric. Our approach ensures affordable biodiversity protection throughout the water column and can serve as a first step toward the implementation of the recently signed High Seas Treaty.