Highways England is driving a new initiative which will have wide-reaching benefits for the environment and biodiversity – and the answer lies in the soil.
The company has announced a step change in the way it improves roads, which will breathe new life and colour into the verges and land around the country’s motorways and major roads – a policy which will cover hundreds of miles in the second road investment period.
The key is creating the type of soils on the verges and roadsides which encourage the growth of wildflowers. More fertile areas with lots of topsoil – rich in potassium, phosphorus and nitrogen – favour aggressive grasses, dock and nettle, which are all fast-growing plants that can out-compete delicate wildflowers for water, nutrients, space and light.
On all major schemes, contractors are now being instructed to follow a new Low Nutrient Grasslands policy aimed at keeping away the ‘bullying’ plant species which love high nutrient soil, and allowing wildflowers to thrive, creating vital habitat for insects and other wildlife.
Highways England Environmental Advisor Ben Hewlett said:
Wildflowers thrive on low nutrient soil and the new policy is focused around the management of topsoil – or rather removing it from new grassland areas to lower the nutrient level, creating the perfect conditions for the flowers.
Removing soil nutrients slows growth rates of vegetation, reducing mowing and management requirements, while improving biodiversity by allowing wildflowers to germinate and thrive without competition from more vigorous plants.
The new initiative will see all grassland areas on improvement schemes finished with subsoil or bare substrate such as chalk. These will then be allowed to regenerate naturally or be seeded with wildflowers and grasses appropriate to the substrate type to create open grasslands high in biodiversity, which in turn support pollinators and other wildlife, while providing road users with a more aesthetic landscape.
By adopting this new policy, Highways England is hoping to:
- improve safety by reducing the number of maintenance visits;
- reduce the carbon footprint through fewer maintenance visits;
- maximise grassland biodiversity of new construction projects;
- reduce long-term maintenance costs by reducing vegetation growth;
- capitalise on potential cost savings by eliminating the need for topsoil import and haulage.
The new grasslands initiative is being rolled out on all major projects initially, and will be implemented by Highways England’s supply chain within the Major Projects Project Control Framework on a scheme-by-scheme basis, and the aim is to apply the instruction to operational projects and wider standards in due course.
Over the last few years a number of biodiversity schemes have been undertaken by Highways England, including extensive habitat connectivity planting, species-rich grassland creation and management and a project to protect and promote the habitat of the narrow-headed ant, England’s rarest, on the A38 in Devon.
A Highways England wildflower scheme, the size of eight football pitches and visible during spring and summer along the A38 between Ashburton and Ivybridge in Devon, has won a Pollinator Award in the Big Biodiversity Challenge run by CIRIA (Construction Industry Research and Information Association). The scheme was started in 2018 with seeds from over 20 variety of flowers – including cornflowers, oxeye daisies, yellow rattle and poppies – sown over five hectares of verge, adding to 10 hectares recently created along the A38 and A30 in Devon and Cornwall.
Highways England has also been working with Cumbria Wildlife Trust, to boost pollinator habitats alongside key A roads, including the A590 and A66, and the verges and embankments of the A303 Stonehenge scheme, recently given the green light by Government, will create a flower-rich, six-mile long butterfly highway and large areas of species-rich chalk grassland.
A successful case study is Dorset Council’s Weymouth Relief Road where wide chalk cuttings were left bare, with minimal top soil (max 15mm thick), and seeded with wildflowers that thrive in chalk. These cuttings are now supporting over 140 plant species and 30 species of butterflies and in the 10 years since construction, the verges have required minimal maintenance, some none at all.
Dr Phil Sterling, Building Sites for Butterflies Programme Manager at the Butterfly Conservation charity, said:
Clare Warburton, Natural England’s Green Infrastructure Principal Advisor, said:
Dr Kate Petty, Plantlife’s Road Verge Campaign Manager, said: