Reducing global land-use pressures with seaweed farming

Agricultural expansion to meet humanity's growing needs for food and materials is a leading driver of land-use change, exacerbating climate change and biodiversity loss. Seaweed biomass farmed in the ocean could help reduce demand for terrestrial crops and reduce agricultural greenhouse gas emissions by providing a substitute or supplement for food, animal feed and biofuels. Here we model the global expansion potential of seaweed farming and explore how increased seaweed utilization under five different scenarios that consider dietary, livestock feed and fuel production seaweed usage may affect the environmental footprint of agriculture. For each scenario, we estimate the change in environmental impacts on land from increased seaweed adoption and map plausible marine farming expansion on the basis of 34 commercially important seaweed species. We show that similar to 650 million hectares of global ocean could support seaweed farms. Cultivating Asparagopsis for ruminant feed provided the highest greenhouse gas mitigation of the scenarios considered (similar to 2.6 Gt CO(2)e yr(-1)). Substituting human diets at a rate of 10% globally is predicted to spare up to 110 million hectares of land. We illustrate that global production of seaweed has the potential to reduce the environmental impacts of terrestrial agriculture, but caution is needed to ensure that these challenges are not displaced from the land to the ocean.

Automated summary

Agricultural expansion is a major cause of climate change and biodiversity loss. Seaweed farming in the ocean could reduce the demand for terrestrial crops and greenhouse gas emissions from agriculture. By modeling the global potential of seaweed farming, this study explores how increased seaweed utilization could affect the environmental footprint of agriculture. Results show that a large area of the ocean has the potential to support seaweed farms, and cultivating Asparagopsis for ruminant feed could have the highest greenhouse gas mitigation.