Satellites supporting coastal resilience in Madagascar and Comoros
Across the western Indian Ocean, coastal ecosystems play a vital role in protecting communities, sustaining livelihoods, and responding to climate change. Mangrove forests, saltmarshes, and productive fishing grounds underpin food security, economic activity, and natural climate solutions. Yet these ecosystems are under growing pressure from environmental change and human activity, while reliable, up-to-date data to support decision-making often remains limited.
To help close this gap, a collaborative initiative supported through the Global Development Assistance – Fast EO Co-Financing Facility (GDA-FFF) has demonstrated how satellite Earth observation can provide timely, practical insights for coastal management in Madagascar and Comoros.
Working closely with the World Bank and national stakeholders, European Earth observation service providers delivered new information products designed to support policy, planning, and sustainable development across both countries. The collaboration also ensured that the technical outputs were aligned with ongoing policy dialogue and investment priorities supported by the World Bank.
Revealing Madagascar’s Blue Carbon Potential
Madagascar is home to some of Africa’s largest and most diverse mangrove systems. These coastal forests store large amounts of “blue carbon” ( carbon captured and held in vegetation and soils), while also protecting shorelines, supporting fisheries, and sustaining local communities. Despite their importance, national-scale information on mangrove extent, condition, and carbon storage has historically relied on global datasets that are often too coarse for local planning.
Through the GDA-FFF project, high-resolution satellite imagery was used to map mangroves and saltmarshes along Madagascar’s west coast at multiple points in time. This allowed changes in ecosystem extent to be tracked over more than two decades and provided a clearer picture of where mangroves have been lost, where they have recovered, and where restoration opportunities may exist.
Figure 1 shows the mangrove extent along the western coastline of Madagascar and the latitudinal distribution of mangrove presence as well as the locations of mangrove losses and (natural) recuperation between 2010 and 2020.
Beyond mapping ecosystem extent, the project estimated how much carbon is stored in mangrove vegetation and soils. Biomass was estimated using satellite-based models that combine optical imagery with spaceborne laser measurements, allowing vegetation structure to be assessed consistently across large and remote coastal areas. These biomass estimates were then converted into carbon content and cross-checked using data from NASA’s Global Ecosystem Dynamics Investigation (GEDI) mission, strengthening confidence in the results while highlighting priorities for future field-based validation (Figure 2).
While these results are intended for national and regional-level assessments rather than site-specific accounting, they represent a major step forward in understanding Madagascar’s blue carbon resources. For decision-makers, this information supports climate strategies, conservation planning, and exploration of future blue carbon financing mechanisms.
National institutions of Madagascar responded positively to the improved level of detail. Compared to previously available global products, the new maps offer clearer insights into regional differences and local dynamics. To make the results accessible beyond technical specialists, the project team also developed a user-friendly web platform where stakeholders can explore mangrove extent, carbon stocks, and changes over time through interactive maps, as shown in Figure 3.
Supporting Sustainable Fisheries in Comoros
In the island nation of Comoros, fisheries are central to food security, employment, and economic stability. Most fishing activities take place in coastal and offshore waters that are highly sensitive to environmental conditions such as temperature, productivity, and ocean currents. Managing these resources sustainably requires a better understanding of how fish habitats vary across space and time.
The GDA FFF project addressed this need by developing satellite-based decision-support tools for fisheries management in Comoros. Focusing on two ecologically and economically important species, the project used long-term ocean data to identify where environmental conditions are most suitable for fish populations throughout the year.
The resulting habitat suitability maps reveal seasonal and spatial patterns that are not easily observed from the ground. For example, certain areas consistently offer better conditions during specific months, while others show signs of gradual habitat degradation over time. These insights can help authorities improve fisheries planning, support sustainable harvesting practices, and explore measures to reduce by-catch and protect vulnerable species.
Figure 4 shows the multi-annual habitat suitability index maps for the silky shark based on the environmental envelope of this species.
Crucially, the approach is designed to be adaptable. While demonstrated for two species, the same methods can be extended to others, supporting a broader ecosystem-based management strategy. By translating complex environmental data into intuitive maps and indicators, the tools help bridge the gap between science and policy.
From data to impact
Although the Madagascar and Comoros activities addressed different sectors, blue carbon and fisheries, together they illustrate the value of Earth observation for coastal development challenges. In both cases, freely available satellite data were transformed into practical information tailored to national priorities, delivered within a short timeframe, and aligned with real policy needs.
The project also highlights important next steps.
In Madagascar, stakeholders emphasised the need to complement satellite analysis with targeted field measurements to further reduce uncertainty and support future blue carbon initiatives. In Comoros, the fisheries tools provide a foundation for longer-term monitoring and integration into national management frameworks.
Overall, the GDA-FFF initiative demonstrates how rapid, targeted Earth observation support can strengthen evidence-based decision-making in data-limited contexts. By improving understanding of coastal ecosystems and making information accessible to non-technical users, satellite-based services can help countries better protect natural resources, enhance resilience, and support sustainable economic development across the western Indian Ocean region.
