Groundbreaking Seagrass Map Reveals Global Distribution and Loss
Scientists have produced the first high-resolution map of seagrass ecosystems around the world, revealing that nearly 70% of global seagrass cover is concentrated off the coasts of just five countries. The study, led by researchers at Arizona State University and published in the journal Nature, used satellite imagery and artificial intelligence to map seagrass meadows across two periods: 2019-2020 and 2023-2024.
The team identified a total of 148,506 km² (about 57,340 square miles) of seagrass globally—an area larger than England—with the majority lying in subtidal areas. Only 21% of this seagrass falls within marine protected areas (MPAs), highlighting a critical gap in conservation coverage.
Methodology: AI and Satellite Imagery Power the Map
Jiwei Li, assistant professor at ASU’s School of Ocean Futures and lead author, explained that seagrasses—the only flowering plants in the ocean—have been understudied compared to coral reefs. “Seagrass is an underwater rainforest, but it’s not as shiny and colorful as coral reefs,” Li said, noting that this lack of attention motivated the large-scale mapping effort.
The team trained a deep-learning AI model to identify seagrass from satellite images. Partners around the world corroborated the data using research dives and underwater cameras. The model then analyzed four years of satellite data to generate the high-resolution map.
Key Findings: Concentrations and Losses
The map reveals that the Bahamas, the United States, Australia, Indonesia, and Cuba host the majority of the world’s seagrass. Over the four-year study period, nearly 4% of seagrass cover (5,969 km²) was lost, and an additional 6,220 km² in tropical regions was degraded. Importantly, nearly 80% of seagrass loss occurred outside marine protected areas.
Threats and Restoration Success
Seagrass meadows face threats from marine heat waves, hurricanes, disease, coastal development, and sediment runoff. However, the map also highlights restoration successes: improved water quality in South Bay, Los Angeles, and in Cuba led to natural seagrass recovery. “If the water conditions are good, and there is no disturbance from human activities, it comes back really fast,” Li said. “That gives us hope for seagrass conservation.”
Li emphasized that the data can inform targeted conservation actions, such as establishing new marine protected areas. “Our hope is that these maps enable more data-driven decisions for coastal management and climate mitigation,” he said.