A year-long partnership between the Seychelles Islands Foundation (SIF) and French expedition cruise company Ponant has produced the most detailed satellite-driven portrait yet of Aldabra atoll, with the first mapped images being released to the public this month.
The collaboration, which concluded in April, centred on commissioning high-resolution imagery from WorldView-2, a commercial satellite operated from 770 kilometres above the Earth. SIF says the data has now been processed into four concrete conservation deliverables, all of them directly relevant to how the atoll is managed.
Two of the outputs will change how ecologists understand the atoll. The first is a clean map of freshwater pools on Grande Terre, the largest of Aldabra’s four main islands. The second is a confirmed habitat map for the dugongs that still graze the lagoon seagrass. Aldabra is the only known Seychellois site where the marine mammal still occurs regularly, so the habitat layer will feed directly into the protected-area monitoring plan that SIF already runs through its Seychelles Fishing Authority partnership.
The other two outputs target a longer-running problem. Researchers used the new imagery to take a fresh snapshot of the planned rat and cat eradication campaign, an effort that, if successful, will remove two of the most damaging invasive predators on the atoll. The fourth deliverable maps the broader ecosystem change in the atoll’s lagoon, a feature that covers more than 2,500 square kilometres of protected marine and land area.
WorldView-2’s value to the project is its spectral range. The sensor captures eight multispectral bands, including coastal blue, blue, green, yellow, red and near-infrared. Bands at shorter wavelengths can penetrate the lagoon water column and reveal benthic features invisible from the surface, while the second channel captures high-resolution panchromatic imagery that, once fused with the colour bands, is sharp enough to pick out individual plants and even Aldabra giant tortoises. False-colour composites already published by SIF and Ponant from the May 2025 acquisition show healthy vegetation in vivid green and shallow reef structure in bright red, with depth gradients running from turquoise to dark blue across the lagoon floor.
Aldabra is the largest raised coral atoll in the world by land area, with about 155 square kilometres of land and roughly 2,400 square kilometres of enclosed lagoon that empties and refills twice a day. It sits more than 1,000 kilometres southwest of Mahé and is one of the most undisturbed atolls on the planet, in large part because its isolation, rough terrain and lack of freshwater kept permanent settlement out. It was inscribed as a UNESCO Natural World Heritage Site in 1982 and is managed as a special reserve by SIF. The atoll hosts the world’s largest population of Aldabra giant tortoises and is the only place in the Western Indian Ocean where both giant tortoise and flightless bird lineages survive.
Ponant, which runs regular expedition cruises that include Aldabra landings under SIF biosecurity conditions, funded the imagery and the associated analysis. SIF has committed to publishing the full set of findings in the coming months, with TCarta leading the core technical work on the imagery. The two organisations describe the project as a proof of concept for using commercial remote-sensing data as a routine tool in atoll-scale conservation.
The timing matters. SIF is in the middle of an environmental and social impact assessment covering 2023 to 2026, with the management plan for Aldabra up for renewal in the same window. Having a defensible, repeatable map of the lagoon, the giant tortoise habitat, the dugong range and the invasive-species frontline will give SIF a baseline it can return to every few years, instead of relying on periodic field campaigns alone. Aldabra’s biodiversity, in other words, is no longer something that has to be measured on foot.
Source: SN
Photo: David Stanley, CC BY 2.0, via Wikimedia Commons.
