Highway Magazine – Commentary: Protecting wildlife in highway designs

Because of the impact highways can have on population numbers, mitigation measures that help reduce and prevent fragmentation, increase genetic diversity, and achieve net biodiversity (BNG) gains are vital, explains Terry Wilkinson, Highway Application Engineer, In ACO Water Management.

The construction industry is in a unique position as its actions can directly impact the levels of wild biodiversity in the UK.

According to the 2021 Royal Society for the Protection of Birds (RSPB) report, the UK is the worst country in the G7 in terms of natural wildlife loss due to human activity.

Transport infrastructure, such as roads and railways, is having a detrimental effect on wildlife populations across the UK. Between 2010 and 2020, transportation infrastructure caused a variety of problems including habitat loss, pollution, and fragmentation. In addition, it has also led to an increase in the death rate of road accidents.

In the past 40 years, one in seven of the UK’s wildlife species has become extinct or threatened with extinction.

The Natural England website also found that 40% of our most important habitats and 30% of the rarest species are still in decline. Hedgehogs are a clear example of the impact of transport infrastructure on the environment. The number of hedgehogs in the UK has halved since 2000, with experts reporting that the number of hedgehogs has fallen from 30 million to a million since the 1950s.

Environmental Law 2021

To guard against further damage to our ecosystems, the Environment Act, which became law in November 2021, will put environmental principles into practice. The law aims to protect species and peatlands while promoting biodiversity and the number of forested lands.

One aspect of the law is that it will measure Biodiversity Net Gain (BNG) using the Natural England Scale launched in July 2021. This metric will allow developers and associations to measure how much BNG is being accomplished. The toolkit can be used by any development project, approval body or landowner who needs to calculate the net gain of biodiversity in England.

Super Amphibious Highways

One group of animals that need immediate attention and protection are amphibians.

During their construction and use, roads are responsible for significant loss and fragmentation of biodiversity with amphibians. Where possible, mitigation measures should be put in place to reduce the negative impact on local habitats.

Mitigation measures could include:

  • Materials: The materials must be designed for the species’ environment. For example, surface residues on standard concrete can be fatal to amphibians and so polymer concrete should be used.
  • Habitat Connection: It is important to establish a secure link between habitats and water-borne areas using guide walls and transit tunnels. These allow animals to cross the road safely.
  • Roadblocks and Gullys: Amphibians can become trapped in traditional roadside canyon pots because they naturally tend to move forward along any vertical barriers in their path. Curbing wildlife with a respite can help protect amphibians due to escape ladders or mesh materials.
  • Construction areas: Temporary fencing around construction areas can help prevent animal intrusion into the site and mitigate any danger to site activity. This is of vital importance during breeding and spawning times.

In certain cases, mitigation measures cannot be used, leaving road developers with no choice but to use compensation measures. Compensation measures to develop the remaining habitats into climates suitable for biodiversity is vital if other mitigation measures cannot be used.

When designing roads, the Road and Bridge Design Manual sets out the general requirements for designing a biodiversity highway (LD 118) and the procedures to be followed when assessing and reporting the environmental impacts of a proposed scheme in line with Environmental Impact Assessment (LA 104) guidance.

sustainable drainage systems

Sustainable drainage systems (SuDS) are also an important aspect to consider when protecting biodiversity.

Under Chapter 6 of the CIRIA SuDS Handbook of Habitat (C753), it states that any new SuDS scheme should relate to other habitats to help build and enhance connectivity. By doing so, problems associated with habitat loss and fragmentation within urban areas can be avoided.

In conclusion, minimizing the negative impact of transportation infrastructure on terrestrial biodiversity and habitat is essential to ensure that animals, such as the hedgehog, are protected from extinction.

By including wildlife protection solutions in highway designs, the impact and intrusion on wildlife faces is minimal thanks to simple changes and additions. Ensuring that mitigation measures are in place allows animals to continue to live in their habitats without suffering the consequences of human urbanization.