Chapter 13 Mitigation and enhancement

Mitigation and enhancement | Mitigation

Part 5: Mitigation and enhancement

Chapter 13: Mitigation and enhancement


When all the surveys are complete and the impacts of the development have been assessed, it will be possible for an ecologist to draw up detailed mitigation proposals, which can be used to mitigate the impacts of the development. The Thomson ecological mitigation calendar shows when it is appropriate to undertake mitigation actions including when development activities can be timed to mitigate negative impacts upon protected species.

Why undertake ecological mitigation and enhancement?

There are a number of reasons for undertaking ecological mitigation and enhancement in association with proposed developments. These include:

  • Compliance with wildlife legislation to avoid prosecution for wildlife offences; this tends to be the minimum level of effort required
  • Compliance with best practice guidelines produced by the licensing authority and others; this may be more than might be required simply to avoid prosecution and includes post-development habitat management and population monitoring
  • Mitigation required to obtain a licence from the appropriate licensing authority in order for the development to proceed lawfully; the proposed mitigation would be expected to comply with best practice guidelines
  • Meeting the requirements of the planning authority (planning conditions or section 106 agreement) or licensing authority; this may be over and above the legal minimum and tends to reflect best practice guidelines
  • Compliance with the mitigation measures set out in an Environmental Statement produced under the EIA Regulations (now a legal requirement, regardless of any planning obligations)
  • Satisfying local concerns about proposed developments based on the impact on local wildlife
  • Improving the overall design for the end user of the development by incorporating features which increase contact with nature and wildlife
  • Meeting corporate objectives on biodiversity, such as ensuring no net loss of biodiversity as a result of corporate activities
  • Meeting sustainability targets set out in environmental best practice documents, such as Building Research Establishment Environmental Assessment Methodology (BREEAM) and the Civil Engineering Environmental Quality assessment and award scheme (CEEQUAL)


Ecological mitigation in its broadest sense includes avoidance, mitigation and compensation measures. These are described as follows:

  • Avoidance: this means measures taken to avoid adverse impacts completely, like adjusting the layout of a scheme so that areas of high nature conservation value are not destroyed, or altering the timing of works so that the site is left undisturbed during sensitive times, such as the breeding season.
  • Mitigation: this means measures taken to reduce adverse impacts, such as using pollution interceptors to minimise pollution of watercourses, screens to reduce visual disturbance to birds, tunnels under roads to allow wildlife to pass from one side to the other and so on.
  • Compensation: this means measures taken to offset the damage caused by a development where avoidance and mitigation are not possible, for example by creating new habitat or enhancing existing habitat.


Chapter 13 Mitigation and enhancement
Thomson Handbook Chapter 13 Mitigation and enhancement Mitigation and enhancement | Mitigation