Putting Seagrass on the Map
Across the Western Indian Ocean, a regional collaboration is mapping seagrass, creating the data needed to protect these critical ecosystems
Roughly 1 in 5 fish that people eat will have spent part of its life in a seagrass meadow. Seagrasses cover less than 1% of the ocean floor, yet their sediments store approximately 10% of the carbon buried in the ocean each year. They buffer shorelines from storm surge, improve water quality, provide habitat for fish and other marine life, and support the fishers and communities who live alongside them.
Yet these ecosystems remain among the least understood and least protected of the ocean’s habitats.
Part of the reason is a lack of visibility: Seagrass grows underwater, often in shallow coastal waters, and is easily confused with seaweed or algae. The deeper challenge, though, is data. There are few field-verified seagrass maps. Country-level estimates can vary widely, with figures for the same areas sometimes ranging from a few hundred to several thousand hectares. Without verified baselines, governments cannot reliably monitor seagrass, include it in their climate commitments under the Paris Agreement on climate change, or direct conservation resources where they are needed most.
The Large-Scale Seagrass Mapping and Management Initiative, known as LaSMMI, is helping close that data gap in the Western Indian Ocean, one of the most seagrass-rich regions on Earth. Active in Kenya, Madagascar, Mozambique, Tanzania, and Zanzibar, LaSMMI brings together local research institutions, the University of Southampton, the Western Indian Ocean Marine Science Association (WIOMSA), and The Pew Charitable Trusts. Together, these partners work to:
- Map seagrass using a single standardized method.
- Estimate the carbon stored in these ecosystems.
- Highlight the importance of seagrass conservation as a way for countries to meet biodiversity and climate objectives.
The accompanying video introduces some of the scientists and community members making this work possible.
The initiative’s highly collaborative approach to mapping is built on success within the region. In 2021, Seychelles committed to mapping and protecting 100% of its seagrass ecosystems by 2030, which led to the development of the first field-verified seagrass map and comprehensive carbon assessment for seagrass in Africa. That work identified approximately 160,000 hectares (about 395,000 acres) of seagrass meadows. These meadows store about the equivalent of 510,000 tons of carbon dioxide each year, an amount nearly equal to the country’s annual energy sector emissions and almost three times its annual transportation sector emissions.
The Seychelles seagrass conservation commitment shaped LaSMMI’s development and showed what governments can do when they leverage scientific evidence. Now, the maps and carbon estimates LaSMMI produces will be tools that countries can use to better protect seagrasses and safeguard these critical ecosystems for generations to come.
Stacy Baez works on The Pew Charitable Trusts’ advancing coastal wetlands conservation project.
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