Mitigating the impacts on wildlife

Potential Impacts of Highway on Wildlife

Transport infrastructure can have negative impacts on wildlife populations, either through habitat loss, fragmentation or pollution. 

The council has a duty through the Natural Environment and Rural Communities Act 2006 (NERC Act) and the Environment Act (2021) to provide for the enhancement and improvement of biodiversity. 

The Environment Act 2021 (“Act”) contains provisions for the protection and improvement of the environment, including introducing mandatory biodiversity net gain (BNG). BNG is an approach to development, and/or land management, that aims to leave the natural environment in a measurably better state (10%) than it was beforehand. 

The council is considering whether and how BNG might apply to highway land proposed for adoption prior to agreeing an approach.

Roads can create barriers to the movement of wildlife, and animals can become trapped in traditional highway assets. Mitigation measures that help prevent habitat fragmentation and enable wildlife to navigate highway are an important part of road design and should be discussed at an early stage with planning ecologists and the council to ensure effective provision of infrastructure and achieve biodiversity net gain. Specialist ecological advice should be sought during the design phase.

Rainfall runoff from highway and spillages caused by accidents can have negative impacts on nearby watercourses and associated wildlife. This risk can be mitigated through the provision of filter strips or other proprietary water treatment systems (see “Highway Drainage Systems”). The council does not typically adopt such interventions.

Principles of Mitigating Impacts

Consideration must be given through the design process to the measures required to help reduce these impacts. The requirement for mitigation will be assessed through the production of an Environmental Impact Assessment as part of a planning application. The council will facilitate the inclusion of mitigation measures as part of the highway aspect of new development. 

The council requires that best practice mitigation measures, such as mammal passes, inset kerbs, tunnels, drains with wildlife exit routes, and arboreal hop-overs are incorporated along known or potential wildlife corridors.

Any mitigation measures, such as badger or amphibian tunnels, must meet the principles of good asset management regarding durability and ease of maintenance, this work should be discussed with the appropriate specialists and the council at an early stage.

National Guidance on Protecting Wildlife

Guidance can be found on environmental design and construction of road schemes in LA 117 of the Design Manual for Roads and Bridges (DMRB). This guidance should be used to help identify areas and issues where environmental factors must be carefully considered. Ciria’s “Environmental good practice on site guide” (C741) provides practical advice about managing construction on site to minimise environmental impacts.

Some plants and animals are given special protection under UK and European law, and LA 108, 115 and 118 of DMRB will give detailed information and advice. These documents will provide information on who must be consulted, together with other advice including: 

  • Annex 1 - Seasonal constraints on animals including birds and fish; 
  • Annex 2 - List of the relevant conventions and legislation; 
  • Annex 3 - Species advice; 
  • Annex 4 - Habitat advice.

There are also British Standards relating to biodiversity:

  • BS 42020:2013, Biodiversity. Code of practice for planning and development;
  • BS 8683:2021 A process for designing and implementing Biodiversity net gain. 
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