SPARC GIScience Lecture Series

Lecture Title: Global high-resolution mapping of seagrass to support conservation

Speaker: Jiwei Li, Assistant Professor, ASU School of Ocean Futures 

About the Talk: Seagrass ecosystems underpin coastal biodiversity and provide vital ecosystem services, including shoreline protection, food security and climate mitigation. Despite growing recognition as a nature-based climate solution, seagrasses are among the least mapped and most poorly understood vegetated coastal ecosystems. We present, to our knowledge, the first global 10-m spatial resolution maps and change analysis of seagrass extent in clear, shallow coastal waters, derived from 4.75 million Sentinel-2 MSI satellite images for two periods (2019–2020 and 2023–2024). Using a deep-learning classifier trained on curated reference data, we identified 148,506 km2 of seagrass globally, including 5,961 km2 of intertidal and 142,545 km2 of subtidal areas. Sixty-nine per cent of global seagrass extent is concentrated in The Bahamas, Cuba, the U.S., Australia and Indonesia, yet only 21% of seagrass areas are located within marine-protected areas. Over the four years of the study, 5,969 km2 (4%) of seagrass was lost, and an additional 6,221 km2 (4.2%) was degraded from dense to sparse cover in tropical regions. Our findings identify seagrass meadow hotspots and vulnerable regions to inform conservation and climate policy.

Speaker Bio: Jiwei Li is a remote sensing scientist, biological oceanographer and computer scientist. Li’s research stands at the forefront in exploring interactions between human and natural systems, especially at the land-ocean interface. Li combines remote sensing with globally scalable physical analytical algorithms, big data analysis, cloud computing, and machine learning to understand the influences of human activities on the aquatic systems to protect the Earth’s resources and achieve a more sustainable future.