A new scientific study has revealed that World War II ammunition dumps on the seabed—long regarded solely as hazardous legacy sites—also support surprisingly rich marine biodiversity. 

The findings suggest that, in addition to posing management and safety concerns, these munitions fields may now function as unintentional artificial reefs hosting complex ecological communities.

A hidden seascape of life

Researchers investigating underwater ammunition dumps discovered that corroding shells, casings and debris provide a structural habitat similar to natural rocky reefs. The scattered objects create hard surfaces where algae, sponges, bryozoans and soft corals can attach. These communities, in turn, attract invertebrates and fish, forming multilayered ecosystems that have expanded over the decades.

The study documents higher-than-expected species richness, including organisms typically associated with stable hard-bottom habitats. Observations indicate that even highly irregular piles of munitions can develop into functioning reef structures over time, as marine life colonises cavities, vertical faces and sheltered spaces.

Ecological value versus risk

The research does not downplay the hazards associated with underwater munitions, which include chemical contamination, metal corrosion and the risk of disturbance. However, it highlights a difficult conservation paradox: efforts to remove old ammunition could inadvertently destroy thriving habitats that have grown around them for more than 70 years.

In some locations, the dumps now harbour species of ecological interest and may even serve as local biodiversity hotspots. The findings underscore the importance of site-specific assessment, balancing environmental risk, habitat value, and safety. Blanket removal policies could overlook the ecological functions these structures have acquired.

A new perspective

Historically, underwater ammunition dumps have been viewed solely through the lens of pollution and hazard management. This new research broadens the perspective by showing how marine ecosystems adapt to anthropogenic substrates. The colonisation of munitions by reef-building species mirrors patterns observed on shipwrecks, concrete debris and offshore installations.

For marine managers and conservationists, the study suggests that some ammunition dumps may now play a more complex role in coastal and shelf ecosystems than previously recognised. Understanding these dynamics will be essential as governments plan remediation strategies in coming decades.