Abstract
In 2020, the Joint Nature Conservation Committee (JNCC), Natural England (NE) and the Department of Agriculture, Environment and Rural Affairs in Northern Ireland (DAERA) published advice to competent authorities on what could constitute significant disturbance within harbour porpoise Special Areas of Conservation (SACs) in England, Wales and Northern Ireland marine areas. In addition, guidance was provided on a noise management approach, based on area-time thresholds of disturbance, to keep underwater noise within levels that do not affect a site’s integrity. A key element of that approach is the estimation of the disturbance footprints resulting from impulsive noise-generating activities within and around the SACs. The recommendation was that for each activity of concern, a fixed Effective Deterrence Range (EDR) would be used to estimate the area where harbour porpoise could be disturbed or deterred. Default EDRs were recommended for seven broad categories of activities, informed by published empirical ranges where the bulk of the effect (reduction in porpoise vocal activity or sightings) had been detected.
There was also a commitment in the guidance to regularly review the suitability of the EDRs, considering emerging evidence such as that gathered through monitoring and research. The first such review was conducted in 2025 through two commissioned reports: Brown et al. (2025) and Majewska et al. (2025). The aim of these was to recommend default EDRs, through a review of the evidence underpinning the current EDRs and subsequently published studies (empirical and modelled) and, where possible, through revisiting existing data with the aim of defining EDRs in a more standardised way.
JNCC, NE and DAERA have considered the outcomes of the two reports, the robustness of the evidence reviewed and the remaining uncertainty. The updated EDRs (Table 1) provided in this advice note remain precautionary but they are more robustly underpinned by the existing evidence than those in 2020. In addition to updating the seven EDRs provided in 2020, this advice introduces twelve new EDRs. Some of these sub-divide previous noise sources while others relate to noise sources not previously considered.