Mapping Island Mangrove Futures for Coastal Risk Reduction in the Asia-Pacific

Challenge

Coastal communities depend on mangroves, yet land use change and climate hazards threaten future protection and benefits.

Solution

Build 2050 land‑cover scenarios and map mangrove ecosystem services to inform hazard mitigation and adaptation choices.

Overview

Mangroves buffer coasts from storm surge and waves, store blue carbon (organic carbon in marine ecosystems), and support livelihoods. Planning for their future requires more than snapshots of current cover.

This project, supported by the Asia‑Pacific Network for Global Change Research (APN), was led by Shizuka Hashimoto (The University of Tokyo, Japan). The project developed spatially explicit 2050 scenarios for island mangroves and quantified how key ecosystem services might change under different land‑use trajectories and pressures.

The work covered six island locations grouped across five country teams: Ba River Delta (Fiji), Andaman Islands and estuarine island mangroves in Odisha (India), Ishigaki Island (Japan), Oriental Mindoro (Philippines),  and Tamsui River Estuary (Taiwan). In each site, the project team prepared land use/land cover (LULC) baselines, analyzed past change, and constructed exploratory scenarios to 2050 reflecting local drivers from social, environmental, economic, and policy domains.

The team then mapped priority mangrove ecosystem services using the InVEST toolset (Integrated Valuation of Ecosystem Services and Tradeoffs) and related methods, producing indicators for coastal vulnerability reduction, carbon storage, sediment retention, nutrient retention, and habitat quality.

Study approach and toolset

Each site used a common workflow adapted to local data: assemble and classify LULC datasets, assess accuracy, and build scenario assumptions with local partners; simulate 2050 LULC; and run ecosystem service models to produce comparable maps. The InVEST coastal vulnerability model connected mangrove extent and configuration with exposure to waves and surge. Carbon storage estimates summarized aboveground and belowground pools associated with different LULC classes.

Sediment and nutrient retention models provided indicators of regulating services that affect water quality and reef health. Habitat quality indices captured the condition of mangrove ecosystems under alternative futures. The resulting maps and statistics were designed for decision support rather than prediction, helping agencies weigh trade-offs among conservation, restoration, and development.

Site highlights (selected)

Ba River Delta, Fiji

Island delta mapping linked mangrove condition with exposure to coastal hazards, supporting targeted nature‑based interventions in vulnerable zones.

Andaman Islands and Odisha, India

Historical LULC analysis and scenario mapping identified areas where mangroves risk conversion to built‑up uses and where restoration could reconnect patches. Drivers of change were prioritized through participatory assessment to guide conservation and ecosystem‑based adaptation.

Ishigaki Island, Japan

Ecosystem service mapping captured both regulating and cultural services, showing how changes in mangrove extent and use could alter protection, carbon storage, and locally valued experiences.

Oriental Mindoro, Philippines

Scenario maps and service estimates highlighted trade‑offs between coastal development and mangrove protection, informing options for hazard mitigation and adaptation planning.

Tamsui River Estuary, Taiwan

Custom land‑use reclassification enabled mangrove mapping in a data system that lacked a dedicated mangrove class, allowing service assessments tailored to the estuary context.

Outcomes and results

• Maps produced for historical LULC change, 2050 land‑use scenarios, and 5 ecosystem services (coastal vulnerability reduction, carbon storage, sediment retention, nutrient retention, habitat quality) at all study sites.
• Developed understanding of historically and locally important drivers of mangrove loss, with site-specific conservation and restoration priorities.
• Land‑use scenarios simulated the future extent of mangrove cover and mapped likely changes in ecosystem services under alternative pathways.
• Capacity built through training: 4 doctoral students and 1 master’s student were supported.
• Research outputs completed: over 14 peer-reviewed articles,  7 book chapters and detailed case reports for the five study sites were published drawing on project work.
• Partnerships expanded: collaboration with the International Union for Conservation of Nature (IUCN) and UNESCO and joint workshops for outreach; roundtable sessions held with local stakeholders to disseminate results.

Project details

Acknowledgements

This project was supported by the Asia-Pacific Network for Global Change Research (APN) under its Collaborative Regional Research Programme (CRRP). Acknowledgments also go to the Institute for Global Environmental Strategies (Japan), National Environmental Engineering Research Institute (India), Wildlife Institute of India (India), University of the Philippines (Philippines), National Taiwan University (Taiwan), Research Institute for Humanity and Nature (Japan), and WWF‑Pacific (Fiji).