Due to the impact highways can have on population numbers, mitigation measures that help limit and prevent fragmentation, increase genetic diversity, and achieve biodiversity net gain (BNG) are vital necessities, explains Terry Wilkinson, highways application engineer, at ACO Water Management.
The construction industry is in a unique position where its actions can directly impact the levels of wild biodiversity in the UK.
According to a 2021 Royal Society for the Protection of Birds (RSPB) report, the UK is the worst G7 country for natural wildlife lost due to human activity.
Transport infrastructure, such as road and rail, has a detrimental impact on wildlife populations across the UK. Between 2010-2020, transport infrastructure has caused a variety of issues including habitat loss, pollution, and fragmentation. As well as this, it’s also increased road traffic mortality.
In the last 40 years, one in seven of the UK’s wildlife species have either become extinct or threatened with extinction.
Natural England has also found that 40% of our most important habitats and 30% of our rarest species are still declining. Hedgehogs are a clear example of the impact transport infrastructure is having on the environment. The number of hedgehogs in the UK has halved since 2000, with experts stating that the population has dropped from 30 million to one million since the 1950s.
The Environment Act 2021
To protect against further damage to our ecosystems, the Environment Act, which became law in November 2021, will put environmental principles into action. The act aims to protect species and peatlands while boosting biodiversity and the number of woodlands.
One aspect of the act is that it will measure biodiversity net gain (BNG) by using a Natural England metric that was launched in July 2021. This metric will allow developers and associations to measure the amount of BNG accomplished. The toolkit can be used by any development project, consenting body or landowner that needs to calculate biodiversity net gain in England.
Super Amphibian Highways
One group of animals that needs immediate attention and protection is amphibians.
During their construction and use, roads are responsible for considerable loss and fragmentation of biodiversity with amphibians. Wherever possible, mitigation measures should be put in place to limit the negative impact on local habitats.
Mitigation measures can include:
- Materials: Materials should be tailored for the species' ecology. For example, surface residues on standard concrete can be fatal to amphibians and so polymer concrete material should be used.
- Habitat connectivity: It is important to create a safe link between habitats and water-borne areas by using guide walls and crossing tunnels. These allow animals to cross the road safely.
- Road kerbs and gullies: Amphibians can become trapped in traditional roadside gully pots due to them being naturally inclined to proceed along any vertical barriers in their way. A wildlife kerb with a recess can help protect amphibians due to their escape ladders or mesh material.
- Construction areas: Temporary fencing around construction areas can help prevent animal incursion into the site and mitigates any danger to site activity. This is of vital importance during breeding and spawning times.
In certain situations, mitigation measures cannot be used, leaving road developers with no choice but to use compensation measures. Compensation measures to grow the remaining habitats into suitable climates for biodiversity are vital if other mitigation measures cannot be used.
When designing roads, the Design Manual for Roads and Bridges guidance outlines general requirements for biodiversity design on the highway (LD 118) and procedures to follow when assessing and reporting on the environmental effects of a proposed scheme in line with the Environmental Impact Assessment directive (LA 104).
Sustainable Drainage Systems
Sustainable Drainage Systems (SuDS) are also a crucial aspect to consider when protecting biodiversity.
Under Chapter 6 of the Habitat guidance in CIRIA’s SuDS Manual (C753), it states that any new SuDS scheme should link to other habitats to help build and enhance its connectivity. By doing this, problems associated with habitat loss and fragmentation within urban areas can be avoided.
To conclude, decreasing the negative impact transport infrastructure has on wild biodiversity and habitats 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 wildlife faces are minimal thanks to simple changes and inclusions. Ensuring mitigation measures are in place allows animals to continue living in their habitats without suffering the consequences of human urbanisation.
