Marine INNS Risk Assessment for Navigational Dredging and Disposal Activities

APEM Group supported Natural England with a comprehensive risk assessment of the dredging pathway, evaluating the risk of marine invasive non-native species (INNS) spread associated with navigational dredging and disposal activities. Drawing on our expertise in marine ecology services, invasive non-native species management, and environmental risk assessment, this project delivered the first detailed evidence base of its kind in the UK, helping to inform national guidance, strengthen marine biosecurity, and support sustainable dredging operations.

Project Summary

Navigational dredging is essential to maintain safe and efficient ports, harbours, and waterways, forming a key part of ports and harbours infrastructure. However, its role as a pathway for the spread of INNS remains poorly understood.

Natural England commissioned APEM Group to undertake a detailed evidence review and risk assessment to better understand how dredging and disposal activities could contribute to INNS introduction and spread, supported by our experience in INNS, dredging and marine licensing.

Using a science-led and collaborative approach, APEM Group identified key risk pathways and developed practical recommendations to support biosecurity planning, regulatory advice, and future research to address remaining evidence gaps

Project Context

Marine INNS pose a significant threat to biodiversity, ecosystem stability, and coastal economies. Managing these risks is a key focus of marine environmental impact assessment. While other pathways such as shipping and aquaculture have been widely studied, navigational dredging has received limited research and regulatory attention.

Dredging activities can create several potential pathways for INNS transfer. These include vessel movements, dredging equipment, and the relocation of sediment to disposal sites. Risk is particularly relevant in coastal and marine development projects, where dredged material may be reused for coastal defence or habitat creation.

Natural England required a clear evidence-based understanding of these risks to ensure that guidance to regulators and industry is accurate, consistent, and aligned with current environmental policy.

Key Insights

First of its kind

First comprehensive UK assessment of INNS risks linked to navigational dredging and disposal

Evidence base

Review of peer-reviewed research and grey literature

Engagement with industry stakeholders to validate operational insights

Framework development

Detailed pathway analysis covering entrainment, transport, survival, and establishment of INNS

All images used in this case study are for illustrative purposes only and do not depict the project featured.

Large yellow floating excavator mounted on a barge in calm coastal waters, with its oversized bucket suspended above the surface. Black support piles rise from the vessel, and the machine is reflected in the water under a clear blue sky.

Project Challenges

Delivering a robust and practical assessment required overcoming several challenges:

Limited existing research on dredging as a pathway for INNS spread

Complex and variable dredging operations affecting risk

Need to adapt existing pathway analysis methods to a new application

Expanding project scope as additional risk factors were identified

Requirement to provide outputs that support both scientific credibility and regulatory use

Solution

APEM Group brought together specialists from its INNS team, marine consultancy, and maritime advisory experts at NASH Maritime, a specialist consultancy within the Group, to deliver a comprehensive solution.

Evidence-led review

Detailed review of scientific literature and industry reports

Interviews with key stakeholders to capture real-world dredging practices

Integration of internal expertise in marine ecology and INNS risk and management

Pathway risk assessment

Step-by-step assessment of the dredging process

Identification of conditions required for INNS to:

enter dredging systems

be transported via vessels and sediment

survive disposal processes

establish in new locations

Evaluation of risk according to site conditions, dredging methods, and species characteristics

Biosecurity and mitigation framework

Identification of high-risk activities and locations

Assessment of potential impacts on protected sites and wider marine environments

Development of targeted recommendations for biosecurity, monitoring, and future research

This approach combined scientific rigour with practical application, ensuring outputs could be used effectively by regulators and industry.

Outcomes and Impact

The project delivered measurable benefits for environmental management and regulatory decision- making.

Environmental outcomes

Improved understanding of how dredging contributes to INNS spread

Identification of key transfer mechanisms and risks

Greater insight into survival and establishment potential of invasive species

Commercial and regulatory benefits

Strengthened evidence base for Natural England guidance and advice

Supported development of future guidance on beneficial use of dredged material

Enabled alignment with national marine policy and legislation

Lasting value

Established a framework for future INNS risk assessments

Identified knowledge gaps to guide future research

Provided a foundation for further APEM projects assessing site-specific dredging risks

‘‘

This project helped to address a key evidence gap concerning the mechanisms by which navigational dredging and disposal activities could spread INNS and their potential risks to the marine environment. The report is a valuable output and has been shared with the ports sector through the UK Major Ports Group and the British Ports Association. We also continue to share it with our staff working on relevant projects within Natural England. The findings helped to consolidate Natural England’s sustainable development casework advice for dredging and associated disposal activities. We welcomed APEM’s approach to the project, the quality of the literature review and direct engagement with stakeholders, as well as the expert knowledge available within the team to develop the evidence.

Jan Maclennan – Senior Specialist (Marine recreation and Marine Invasive Species)

Natural England

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Supporting Sustainable Dredging and Marine Biosecurity

This project highlights how APEM supports sustainable marine development by combining ecological expertise with practical industry knowledge.

We help clients to:

Identify and manage invasive species risks in marine environments

Implement effective biosecurity planning and mitigation strategies

Meet regulatory requirements with confidence

Balance operational needs with environmental protection

Additional Support

APEM’s INNS specialists deliver tailored, evidence-based support across marine, freshwater, and terrestrial environments.

Our services include:

INNS risk and impact assessments for marine and dredging activities

Biosecurity planning and implementation

Monitoring, surveillance, and mapping of INNS

Rapid response and contingency planning

Development of bespoke frameworks for regulatory compliance

Our adaptive approach ensures that INNS management strategies remain effective as risks evolve. This helps reduce environmental impact while supporting efficient project delivery and long-term cost savings.

View the Natural England report here: https://publications.naturalengland.org.uk/publication/5042533200297984

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