Mapping the Invisible: How the Pew Charitable Trusts’ Seagrass and Mangrove Survey Is Reshaping Jamaica’s Coastal Policy

Briefing

• Pew Charitable Trusts supports first comprehensive seagrass and mangrove mapping of Jamaica.
• Data covers both coasts and provides baseline for measuring future change.
• Mangrove loss estimated at 770-plus hectares between 1996 and 2006; decline continues.
• Seagrass meadows support sea turtles, manatees, and juvenile fish across multiple parishes.
• Data is being used to inform Jamaica’s NDC 3.0 coastal ecosystem commitments.

You cannot manage what you cannot measure. For Jamaica’s coastal ecosystems — the mangrove forests and seagrass meadows that buffer shorelines, support fisheries, and sequester carbon at rates that make them among the most ecologically valuable habitats on the planet per unit area — the measurement problem was acute. Decades of environmental monitoring had produced partial data: surveys of specific sites, inventories conducted as part of environmental impact assessments for individual development proposals, academic research on particular reef or wetland systems. What Jamaica lacked was a comprehensive, nationally consistent baseline against which change could be tracked and management decisions could be calibrated.

The Pew Charitable Trusts’ Ocean programme, working in partnership with Jamaican government agencies including the National Environment and Planning Agency and the Fisheries Division, undertook to fill that gap. The mapping project, which involved satellite imagery analysis supplemented by intensive field verification work, produced the most comprehensive picture yet available of the extent and condition of Jamaica’s coastal wetlands. The results were significant both in what they showed about the current state of the ecosystems and in what they provided as a foundation for future monitoring and policy.

What the Data Shows

The mapping confirmed that Jamaica has lost more than 770 hectares of mangrove cover since 1996, with the losses concentrated in areas of intense coastal development, particularly along the north coast and around the Kingston metropolitan area. The remaining mangrove stands are distributed unevenly, with significant concentrations in the Portland Bight area on the south coast — which contains Jamaica’s largest remaining mangrove forest — and in Portland parish on the north-east coast. Several of the larger mangrove systems along the resort-heavy north coast have been severely reduced or fragmented by development.

The seagrass mapping revealed extensive meadows in shallow inshore waters around much of the island’s coast, with particularly significant beds in Portland Bight, along the southern St Elizabeth coast near Treasure Beach, and in shallow embayments along the north coast. The seagrass beds support the island’s remaining West Indian manatee population, provide key foraging habitat for green sea turtles, and function as nursery ground for juvenile snapper, grouper, and other commercially important fish species.

From Data to Policy

The significance of the Pew mapping work extends beyond what it reveals about the current state of Jamaica’s ecosystems. It provides, for the first time, a baseline against which the effectiveness of conservation commitments can be measured. Jamaica’s NDC 3.0, submitted in late 2025, included specific targets for mangrove restoration and seagrass protection. Without the Pew baseline data, those commitments would have been assertions without measurement. With it, the government, civil society, and international partners can track whether the commitments are being honoured in practice, and can identify specific areas where management intervention is most urgently needed.

The data is also relevant to the planning decisions that will determine whether Jamaica’s coastal ecosystems continue to decline or begin to recover. Every EIA for a coastal development project should now be assessed against the Pew baseline: does this development’s footprint overlap with mapped seagrass or mangrove? Does the construction methodology adequately protect adjacent wetlands from sediment and nutrient runoff? The baseline makes these questions answerable in a way they were not before. Whether the planning system will ask them consistently is a different question.

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