New seabed maps support long-term conservation around Ascension Island
The British Geological Survey (BGS) has delivered the first ever marine geology and habitat maps for Ascension Island – an isolated volcanic island located south of the equator in the South Atlantic Ocean. These new maps mark a significant step forward in understanding and protecting one of the world’s largest marine protected areas (MPAs).
The Ascension Island MPA covers a vast expanse of largely untouched ocean and supports a unique mix of deep-sea and open-ocean habitats, many of which remain unexplored. The surrounding waters are home to species found nowhere else on Earth, while the island itself provides nesting grounds for thousands of turtles and seabirds.
As part of the project, BGS conducted high-resolution bathymetry surveys and drop-camera sampling in the island’s nearshore areas. In several locations, the team collected data in areas that had never been surveyed before – providing valuable insights not only for conservation, but also for improving maritime safety.
Sandy sediments and rocky outcrops
Funded by the UK Government, the project brought together data from both BGS and the Royal Navy, including bathymetry (depth), backscatter (seabed composition) and ground-truth sampling (underwater video), to produce a comprehensive suite of geological outputs.
The resulting maps – covering seabed substrate, geomorphology and habitats – provide the first detailed picture of nearshore features around Ascension Island. They reveal a range of previously unmapped volcanic, erosion-depositional and coastal formations, including seamounts, lava flows, ridges, submarine landslides, channels, sandy sediments and rocky outcrops – many of which serve as vital habitats for marine life. Together, these outputs enhance understanding of the island’s seabed and geological processes and lay the foundation for long-term habitat monitoring and environmental management within the MPA.
Adapting existing technology
As part of the project, the BGS Marine team trained the Ascension Island Government (AIG) in using GIS software to view, edit and manage the data. This enables AIG to update the maps as new information emerges or management needs evolve. Despite its rich biodiversity, the region remains vulnerable to human activity and climate change. These maps will be a vital tool for the AIG Conservation team in protecting the area.
“Collecting data in such a remote and exposed location was a challenge, but an absolute privilege and pleasure. BGS had to adapt existing technology to work with the available survey platform within the limits of Ascension’s wonderfully varied and unpredictable operating environment,” commented Rhys Cooper, BGS project manager and senior surveyor.
Catriona Macdonald, BGS marine geoscientist, said: “The collection of new high-resolution datasets around Ascension Island allowed us to map the seafloor geology in unprecedented detail, uncovering critical geological features and habitats that support a rich diversity of marine life, and marks a significant milestone in our understanding of Ascension Island’s marine environment.”
The final maps were submitted to the AIG Department of Conservation in February 2025 to support the ongoing protection of its marine environment.
