The Ascension Island Marine Protected Area (MPA) is one of the largest areas of protected ocean in the world and safeguards a unique ecosystem in the south Atlantic Ocean. It supports many species that are found nowhere else on Earth in a mixture of deep sea and open ocean habitats that remain largely untouched and unexplored, whilst the island itself is home to thousands of nesting turtles and sea birds.
The British Geological Survey (BGS) recently completed a programme of high-resolution bathymetry surveys and drop-camera sampling within the nearshore areas of the island. The survey team even managed to collect data where no other survey had ever been undertaken before, which, in addition to supporting conservation efforts, will enable safer navigation in future.
Funded by the UK Government, the project utilised both BGS and the Royal Navy’s bathymetry (depth) and backscatter (seabed composition) data alongside ground-truth sampling (underwater video footage) and many other derived data layers to create a suite of bespoke geological outputs. The maps, which include seabed geology (substrate and geomorphology) and habitat, are the first to be created for the island and determine the character, distribution and extent of the nearshore habitats of the MPA.
The geomorphological map reveals a collection of previously unmapped volcanic, erosion–depositional and coastal features including seamounts, submerged lava flows, ridges, submarine landslides and channels. Meanwhile, the substrate map focuses on the nearshore areas, which are composed of the sandy sediments and rocky outcrops that are fundamental habitats for the marine communities. Both maps have enhanced the understanding of both seabed and geological processes occurring around Ascension Island, enabling the creation of seabed habitat maps that provide unprecedented insight into the diverse ecosystems present in the surrounding waters.
As part of the project, the BGS Marine team provided training to the Ascension Island Government (AIG) in how to effectively use GIS software to view, edit, query and manipulate the data. The intention is for AIG to modify these maps as new data and knowledge become available and the management requirements of the protected area change. Although the region is rich in biodiversity, it is one of the habitats most at risk from anthropogenic (human-induced) development and climate change. The maps and data will be a vital resource for the AIG conservation team as they continue to manage and safeguard the region.
Rhys Cooper, project manager and senior surveyor, BGS, said: “Collecting data in such a remote and exposed location was a challenge, but an absolute privilege and pleasure. We had to adapt existing technology to work with the available survey platform within the limits of Ascension’s wonderfully varied and unpredictable operating environment.”
Catriona Macdonald, marine geoscientist, BGS, said: “The collection of new, high-resolution datasets around Ascension Island allowed us to map the sea-floor geology in unprecedented detail, uncovering critical geological features and habitats that support a rich diversity of marine life. This marks a significant milestone in our understanding of Ascension Island’s marine environment.”
The final maps were delivered by BGS to the Ascension Island Government’s Department of Conservation in February 2025 and will be used by the team to manage the marine environment for future generations.
Tiffany Simpson, Director of Conservation and Fisheries, Ascension Island Government, said: “AIG are excited to have access to such high-quality bathymetry and habitat maps. They will be transformative in our nearshore research and monitoring and allow for much more evidence-based conservation management.”
