Policy paper

Reducing marine noise

Published 21 January 2025

The issue

Our seas are becoming increasingly busy. They support our fisheries, tourism, and shipping industries, as well as being a crucial source of renewable energy.

Our seas are also home to diverse and precious marine life including a breadth of marine mammals that play a vital role in maintaining a healthy ecosystem. This includes 28 species of cetacean which have been recorded in the UK. Twelve are regularly seen, including:

• harbour porpoise
• bottlenose dolphin
• killer whale
• humpback whale

We are home to around 38% of the global population of grey seals and up to an estimated 449,000 harbour porpoise. As such, the UK government has pledged to protect the marine environment.

Marine mammals are facing a range of pressures. A key concern is the level of noise generated from a range of human activities including:

• pile driving for offshore wind farm foundations
• seismic surveys
• the detonation of unexploded ordnance from the seabed
• shipping

There is also a growing recognition that noise is impacting upon a wide range of other species, including fish and invertebrates.

In May 2023, international experts came together in a call for governments to take action to reduce man-made noise in our oceans.

What we mean by ‘marine noise’

Natural sound is an important cue within the marine environment. It is used by animals to:

• navigate
• communicate
• find food
• locate mates
• avoid predators

Sounds made by human activities, here referred to as ‘marine noise’, are increasing and can interfere with or obscure the ability of marine animals to hear natural sounds.

Marine noise is made up of impulsive and continuous noise.

Impulsive noise

Impulsive noise is characterised by sounds of short duration and high peak sound pressures (levels) across a broad frequency range. They can be generated by certain human activities such as:

• geophysical surveys
• impact pile driving
• active sonar
• acoustic deterrent devices
• explosive use

Continuous noise

Continuous noise refers to sounds of long duration in the marine environment, such as shipping or the operation of wind turbines.

Both impulsive and continuous noise have the potential for negative effects on marine mammals.

The UK government’s ambition is to be a global leader in managing and reducing marine noise. We want UK waters to be a safe haven for the wealth of marine mammals and noise sensitive species that are resident in our seas.

The UK’s commitments

The UK government has pledged to protect the marine environment and has made a number of commitments.

We have a target to restore at least 70% of protected features in relevant Marine Protected Areas to a favourable condition by 2042, with the rest in a recovering condition under the Environmental Targets (Marine Protected Areas) Regulations 2023. For marine noise, to maintain favourable conditions in harbour porpoise Special Areas of Conservation, we aim to keep noise disturbance below set thresholds. 

Under the Marine Strategy Regulations 2010, we are required to take the necessary measures to achieve or maintain Good Environmental Status in UK waters. This includes achieving Good Environmental Status for underwater noise by reducing both impulsive and continuous noise to levels that do not adversely affect populations of marine animals, as laid out in the UK Marine Strategy.

As the UK is a contracting party to the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR), we have commitments to reduce anthropogenic underwater noise to levels that do not adversely affect the marine environment as set out in the North-East Atlantic Environment Strategy 2030.

More recently, the Kunming-Montreal Global Biodiversity Framework was adopted in 2022. It sets out an ambitious pathway to reach the global vision of a world living in harmony with nature by 2050. One target is to reduce the negative impact of pollution from all sources by 2030 to levels that are not harmful to biodiversity and ecosystem functions and services. Noise is considered to be a source of marine pollution.

We have ambitious targets to meet and therefore are setting out here Defra’s ongoing work and upcoming plans to minimise noise in our seas.

What we have done so far

Across the UK, we are taking action to tackle marine noise.

Managing noise in harbour porpoise Special Areas of Conservation in England, Wales and Northern Ireland

The UK government is committed to ensuring an ecologically coherent and well-managed network of Marine Protected Areas. This means working to ensure the conservation objectives for each protected area are met. The UK has seven Special Areas of Conservation for harbour porpoise, the species often regarded as the most sensitive to marine noise.

To support the existing licensing regime for regulated activities, guidance was published by our statutory nature conservation bodies (SNCBs) in 2020. The guidance introduced noise disturbance thresholds in harbour porpoise Special Areas of Conservation in England, Wales and Northern Ireland and recommended Effective Deterrent Ranges representing the spatial extent of harbour porpoise disturbance from different noisy activities. Recent scientific evidence shows that adherence to the noise disturbance thresholds should avoid a potential adverse effect on the integrity of the protected area.

To maintain the habitat, it is essential that all licensing authorities and industries work together, and industry operates in line with their licence conditions and the mitigation hierarchy to avoid, reduce and mitigate impacts. This includes industries working together to consider the noise they are producing, both individually and collectively, to ensure noise levels do not breach the thresholds.

Preventing harmful blasts at sea

After both World Wars, large numbers of explosives were left undetonated in the marine environment. An increase in marine development is leading to greater detail on the location of these unexploded ordnance (also termed UXO) which need to be cleared to protect human life and infrastructure.

UXO clearance has previously been undertaken through high order detonation. The resulting blast can produce high levels of energy which can result in considerable impacts on the marine environment, including seabed damage, and injury and disturbance to marine species from the associated noise.

In 2021, Defra worked together with devolved governments, licensing authorities and SNCBs to provide the first UK government Joint Position Statement on minimising environmental impacts from UXO clearance. In 2024, a revised Joint Position Statement was published that set out stricter expectations in relation to high order detonations. The Joint Position Statement and its associated guidance should be considered ahead of any marine licence application related to UXO clearance from the seabed.

There are low noise alternatives to high order detonation that are safe, commercially available and cause less environmental harm. As set out in the revised Joint Position Statement, low noise methods of clearance should be the default method used to clear any type of UXO in the marine environment.

If there are extraordinary circumstances which mean a low noise method of clearance cannot be undertaken, applicants should discuss this with the appropriate licensing authority and SNCBs at the earliest opportunity. 

The following UK marine licensing authorities have confirmed that they expect to take this general approach when determining marine licence applications for activities relating to UXO clearance:

• Marine Management Organisation (MMO)
• Marine Directorate of the Scottish Government
• Natural Resources Wales
• Department of Agriculture, Environment and Rural Affairs in Northern Ireland
• Offshore Petroleum Regulator for Environment and Decommissioning.

Monitoring and Research

Monitoring programmes established since 2012 have provided an improved understanding of the levels of impulsive and continuous noise pollution in UK waters, with the UK Marine Noise Registry recording data on impulsive noise sources since 2015.

Defra has been working closely with scientists and advisors to deliver a dedicated programme of research. Since 2021, over 30 noise-related research projects have been funded through the Offshore Wind Enabling Actions Programme, with many more projects being steered and overseen through Defra’s involvement in a wide variety of other initiatives and programmes across the UK. This will continue to build our understanding of marine noise impacts on a wide range of species and identify where interventions are required. This will provide valuable evidence to support our decision-making.

The research reports published to date can be viewed online:

• Impacts of underwater noise from offshore wind - ME5610
• Management of underwater noise from offshore wind - ME5611

Next steps

It is vital that biodiversity is protected whilst meeting the important commitments to achieving net zero and supporting thriving industry. The UK government encourages all marine industries to take all necessary steps to reduce their noise. We plan to implement a series of further actions to support this which are set out below.

Reducing noise from offshore wind

The UK government has ambitions to radically increase renewables deployment to deliver our Clean Power by 2030 Mission whilst effectively supporting thriving marine and coastal ecosystems. In Defra, we recognise the impact construction on such a large scale can have on our environment, including through noise generated from piling during the installation of wind turbine foundations and offshore substations.

Due to the increased levels of noise anticipated over the coming years, it will be increasingly more difficult to determine no adverse effects on site integrity for harbour porpoise SACs. Industry should expect to see changes in the way noise is managed in the marine area. Industry’s adoption of noise reduction methods during piling will be vital for ensuring that licensing authorities can continue consenting works to go ahead, whilst remaining below the noise disturbance thresholds.

The UK government intends to consult on an offshore wind piling noise limit. Significantly reducing the noise produced during the construction of offshore wind developments will contribute to ensuring our Clean Power by 2030 Mission is delivered sustainably and in a way that continues to protect and enhance our marine environment.

Following the consultation on an offshore wind piling noise limit, Defra intends to work with offshore wind developers throughout 2025 and 2026 to gather data during piling activities to test and refine the outcomes of the consultation. We would welcome offshore wind developers joining this pilot programme. For further information, email: offshorewind@defra.gov.uk.

From January 2025, given the expected increase in noise levels over the coming years, and the above outlined policy commitments, we expect that all offshore wind pile driving activity across all English waters will be required to demonstrate that they have utilised best endeavours to deliver noise reductions through the use of primary and/or secondary noise reduction methods in the first instance.

Primary methods aim to reduce noise emissions at the source through modifications of the piling process (for example, alternative hammer types, alternative foundation types). Secondary methods aim to reduce the noise propagated through the water column during pile driving by employing systems such as casings, resonators and bubble curtains.

Applicants can propose the use of any noise reduction method (primary, secondary, or a combination of methods) in their marine licence application and/or their post-consent requirement discharge request. Technologies with more robust evidence regarding their efficacy and noise reduction capabilities are likely to face smoother consenting journeys with regard to noise related matters. Furthermore, given the current evidence gaps regarding harbour porpoise disturbance, developers can propose alternative Effective Deterrent Range values in their licence applications and/or post-consent requirement discharge requests, provided they are supported by robust evidence appropriate to the case in question. This will be considered by the relevant regulator during application determination in consultation with the relevant SNCBs. The greater the level of evidence provided to support justification of a lower Effective Deterrent Range, the more likely this will be accepted by the regulator. Early engagement with the relevant regulator is strongly encouraged. It remains the case that any and all applications for marine licences will be determined on a case-by-case basis, on the basis of the application that has been made and the individual circumstances.

Amongst other things, a wildlife licence may also be required to undertake piling and may only be granted where the licensing authority is content that it meets the legislative tests: for example, where there is no satisfactory alternative and the activities licensed are not detrimental to the maintenance of the population of the species concerned, at a favourable conservation status in their natural range.

Thorough consideration of noise reduction methods should therefore be undertaken by the applicant, including justification as to why applying noise reduction methods to your activity may not be considered a satisfactory alternative. The additional cost of a noise reduction system is unlikely to be a sufficient justification on its own merit to discount a satisfactory alternative, unless the cost renders the project financially unviable. Any additional justification such as lack of supply chain, contractual obligations, financial milestones, or technological incompatibility should be provided to explain why noise reduction systems are not a satisfactory alternative. Note that as technology develops and the supply chain improves, these arguments are likely to become less valid. This should be submitted to the relevant licensing authority for their consideration when undertaking a review of any application for a wildlife licence.

Developers who have secured the greatest possible noise reductions are less likely to face requests to further explore satisfactory alternatives and therefore delays in consenting, as they have demonstrated they have utilised best endeavours to secure a satisfactory alternative. Any applications for wildlife licences will be determined on a case-by-case basis, on the basis of the application that has been made and the individual circumstances.

Read the joint statement from statutory advisors.

Reducing noise from other sources

Defra recognises the impact that both continuous noise and impulsive noise from other sources can have on marine mammals and is committed to minimising these impacts. Innovations across all industries to minimise noise impacts are therefore encouraged.

We are supportive of the International Maritime Organisation’s Revised guidelines for the reduction of underwater radiated noise from shipping to address adverse impacts on marine life . We will be working across UK government and through research and industry engagement to understand where improvements and changes can be made. As per the Maritime and Coastguard Agency’s Marine Information Note, ships are encouraged to use the International Maritime Organisation’s guidelines in order to minimise the effects of underwater radiated noise and provide feedback on their use, where possible.

We are considering where improvements can be made across all industries undertaking geophysical and seismic surveying activities so that impacts are minimised as far as possible.

Consideration of UK wide noise threshold values

As part of ongoing work to meet our commitments through the UK Marine Strategy to achieve or maintain Good Environmental Status on underwater noise, Defra and the devolved administrations will be considering noise threshold values for introduction across all UK waters for both impulsive and continuous noise sources. 

These threshold values would be levels below which Good Environmental Status on underwater noise is expected to be achieved. These new values would be in addition to what currently exists in some harbour porpoise SACs. Introduction of such new threshold values may lead to changes to how activities are managed in the future, to keep noise below such levels.

We will be working together with devolved administrations, licensing authorities, SNCBs and scientific advisors such as the Centre for Environment, Fisheries and Aquaculture Science to evaluate options for these thresholds. Future introduction of thresholds across all UK waters would cement our existing commitments to reduce marine noise and protect UK waters.

International Cooperation

Many of the cetaceans found in UK waters are part of much larger populations whose range extends beyond UK waters. It is therefore important that we work together with other nations to take action. The UK government will continue working with all other contracting parties to OSPAR to agree a regional action plan for the North-East Atlantic by 2025, setting out a series of national and collective actions to reduce underwater noise pollution.

Outside of the North-East Atlantic, we are working closely with our international counterparts including the US and Australia through international multilateral fora to share information and collaborate on scientific, technological, and regulatory issues as they relate to marine noise.

Who we are working with

We will continue to work closely across the UK government, devolved governments, licensing authorities and SNCBs, as well as international organisations such as OSPAR, to develop and implement deliverable, robust and effective policies.

To develop and refine our work, Defra engages with relevant:

• licensing authorities
• SNCBs
• scientific advisors
• a wide range of industries
• environmental non-governmental organisations
• charities
• research institutions and academics

We will be engaging with industries to determine where noise reductions or modifications can be made. We look forward to continuing to work closely with all interested parties.