First global seagrass map charts where meadows are vanishing
A new Nature study mapped 148,506 sq km of seagrass from 4.75 million satellite images, finding 4% lost in four years and only 21% inside protected areas.
Photo by Joachim Schnürle on Pexels
The first global seagrass map at high resolution was published in Nature on June 24, 2026, showing 148,506 square kilometres of seagrass in clear, shallow coastal water and how that cover changed over four years. Researchers led by Arizona State University’s Center for Global Discovery and Conservation Science built the map from 4.75 million Sentinel-2 satellite images, taken across two periods, 2019 to 2020 and 2023 to 2024, and processed with a deep-learning classifier trained on diver field data. The headline finding is a warning: about 4% of mapped seagrass was lost in four years, and only 21% of it lies inside marine protected areas.
The map records gains as well as losses. Seagrass expanded in South Bay near Los Angeles after a restoration project, and in Cuba as water clarity improved. The picture is one of a fast-moving coastal ecosystem that, until now, had no consistent global baseline to measure against.
What the global seagrass map found
The study, “Global high-resolution mapping of seagrass to support conservation”, maps extent at 10-metre resolution down to roughly 30 metres of depth. It splits the total into 5,961 square kilometres of intertidal seagrass and 142,545 square kilometres of subtidal seagrass, and tracks change between the two survey periods. The table below lists the headline figures as reported by the authors.
| Metric | Figure | Detail |
|---|---|---|
| Total mapped seagrass | 148,506 sq km | Clear, shallow water to ~30 m depth |
| Intertidal seagrass | 5,961 sq km | Exposed at low tide |
| Subtidal seagrass | 142,545 sq km | Permanently submerged |
| Concentration in five countries | 69% | Bahamas, Cuba, USA, Australia, Indonesia |
| Inside marine protected areas | 21% | Most seagrass sits outside protection |
| Lost over four years | 5,969 sq km (4%) | 2019-2020 vs 2023-2024 |
| Degraded, dense to sparse | 6,221 sq km (4.2%) | Tropical regions |
| Satellite images used | 4.75 million | Sentinel-2, 10 m resolution |
Source: “Global high-resolution mapping of seagrass to support conservation”, Nature (June 24, 2026), and Arizona State University.
Most of the world’s mapped seagrass is clustered in a few places. The Bahamas, Cuba, the United States, Australia and Indonesia together hold 69% of the total extent. That concentration makes the global figure sensitive to what happens in a handful of countries.
The protection gap
The map exposes a gap between where seagrass grows and where it is protected. Only 21% of mapped seagrass falls within marine protected areas, and nearly 80% of the loss recorded over the four years happened outside those areas. Much of the decline was linked to human activity, including coastal development in China and fertiliser pollution in Florida.
Beyond outright loss, a further 6,221 square kilometres of seagrass, about 4.2% of the total, shifted from dense to sparse cover in tropical regions over the same window. Thinning meadows store less carbon and shelter fewer fish, so the degradation figure matters alongside the headline loss. The pattern of decline matches the wider conservation case that Winss Solutions set out in 24 bold sustainability trends to watch in 2025 and 2026, where the 30×30 protection target features prominently.
How satellites and AI built the map
The map combines two technologies. Sentinel-2 provides frequent, free, 10-metre optical imagery of coastal waters, and a deep-learning classifier sorts seabed pixels into seagrass or not, after training on data collected by divers. Stacking 4.75 million images across two multi-year periods lets the model see through clouds, waves and changing water clarity, and measure change rather than a single snapshot. The result is a consistent global baseline that earlier, patchy national surveys could not provide.
That pairing of remote sensing and machine learning is the same approach Winss Solutions examined in AI and sustainability, a match made in heaven if well executed, where data quality decides whether the tool delivers. The seagrass maps have been added to the Allen Coral Atlas and released for public use, so conservation agencies can see their own coastlines at the same resolution as the global study.
Seagrass sits inside a broader ocean-health agenda. It supports fisheries, buffers coasts against storms, and stores carbon in its sediment, which is why it falls under SDG 14, life below water, in the 17 Sustainable Development Goals. A reliable map is the precondition for tracking progress against that goal.
About the Center for Global Discovery and Conservation Science
The Center for Global Discovery and Conservation Science at Arizona State University studies ecosystems at large scale using aircraft and satellite sensors paired with field data, and is directed by Gregory Asner, a senior author on the study. Its earlier work includes the Allen Coral Atlas, a global map of shallow coral reefs, which gave the team both the methods and the platform to extend mapping to seagrass. The center funds this work in part through a NASA Jet Propulsion Laboratory research partnership. By publishing a global seagrass map with four-year change detection, the center has given coastal managers the first consistent way to see where meadows are disappearing and where protection is missing, the gap the new data makes hard to ignore.
Sources: Nature; EurekAlert (Arizona State University); ASU News
Featured image: photo by Joachim Schnürle on Pexels (free Pexels license).
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I specialize in sustainability education, curriculum co-creation, and early-stage project strategy. At WINSS, I craft articles on sustainability, transformative AI, and related topics. When I’m not writing, you’ll find me chasing the perfect sushi roll, exploring cities around the globe, or unwinding with my dog Puffy — the world’s most loyal sidekick.
