Biodiversity: A balancing act

Biodiversity across Great Britain is on a steep downward trajectory. The State of Nature Report 2023 shows that since 1970 UK species have declined by around 19% on average, and nearly one in six species (16.1%) are now threatened with extinction.

Counterintuitively perhaps, the land around the country’s 20,000 miles of rail track is home to a wide variety of plant and animal life. Thanks to a lack of public access, the ‘green corridor’ exists as an ecosystem relatively unharmed by mankind’s excesses – a refuge for endangered species including insects, lizards, and mammals. Protecting such sanctuaries is of the upmost importance, and Network Rail is taking concrete steps to regenerate the native wildlife living alongside the rails.

Following the 2018 Varley Review of Network Rail’s approach to vegetation management, in 2019 the Department for Transport’s (DfT) policy paper ‘Enhancing Biodiversity and Wildlife on the Lineside’ challenged the organisation with achieving “no net loss in biodiversity on its existing lineside estate by 2024 and to achieve net gain on each route by 2040”. The organisation was to work “in partnership with its lineside neighbours, local landowners, and environmental groups” to achieve this.

As a first step, Network Rail’s 2020 Biodiversity Action Plan outlined its ambitions for its biodiversity assets, and how it intended to protect, manage, and enhance their condition through CP6 and beyond. It also committed to the DfT’s key goal of no net loss in biodiversity by 2024 and set out a more ambitious task of achieving a biodiversity net gain by 2035.

In the four years since, Network Rail has engaged in numerous programs to protect its biologically valuable lineside assets and improved its communication of such initiatives – another stipulation of the DfT’s policy paper.

Replanting

Since 2019, Network Rail has worked with The Tree Council to ensure its vegetation management practices have a minimal impact on biodiversity. The Tree Council acts as a ‘critical friend’ offering advice on how it can manage its trees while creating wildlife corridors to encourage rewilding.

For example, back in 2018, a series of trial hedgerows was planted at Hadley Wood station on the border between Greater London and Hertfordshire. These mimicked the traditional ‘railway hedges’ made a legal requirement under the Railway Act of 1982 to protect rail lines from livestock. The hedges at Hadley Wood are a mixture of species such as hawthorn, hazel, guelder rose, blackthorn and dogwood, planted using different techniques.

The trial tested three different hedgerow creation techniques: planting whips (young trees), sowing a seed mix, and natural regeneration. Volunteers from the local community planted half of the whips with supervision from The Tree Council, while the other half were planted by contractors provided with a specification.

A review of the project in 2024 found that the sections planted with whips have formed an effective boundary around 3.5 metres high and hedgerow whips have begun producing flowers and fruits, supporting wildlife. However, natural regeneration did not lead to a hedgerow within the expected five-year timeframe, and while a hedgerow can grow from seed within five years, it is not as reliable as whip planting. Further research is needed to optimise the technique.

While this project has yielded promising results, it is not possible to replant along every mile of the railway boundary. Network Rail therefore employs many techniques to improve the diversity of species along the line in other ways. One example is veteranisation – making dead trees safe for the railway and perfect habitats for small creatures.

In 2024, Network Rail has been at work on the Chiltern Main Line from Beaconsfield, Buckinghamshire, to London, cutting trees back to the mandated seven metres from the railway’s edge. While doing so, its tree surgeons have cut away rings of bark low down on the trees, keeping the trunk standing but preventing any growth above stump level. They’ve then recreated some of the features of older trees using modern forestry techniques. For example, they’ve added fake lightening strikes by cutting cracks with chainsaws, and drilled fake woodpecker holes, and knots for creatures to crawl into.

Compensating

However sensitively handled, routine vegetation management risks some loss of habitat. As compensation for this, Network Rail balances the removal of trees and vegetation elsewhere on the railway.

In 2023 it completed a two-year pilot project to enhance the natural habitat near the iconic Glenfinnan viaduct. Network Rail and Forestry and Land Scotland (FLS) invested £300,000 to improve biodiversity in a part of the West Highlands that sits within Scotland’s endangered Atlantic rainforest zone – an area of international importance for biodiverse habitats. These habitats are home to a wide range of notable species including otter, which is a European protected species.

The first phase of work began in early 2023, with the clearing and removing of non-native species, such as rhododendron, across woodland and peatland habitats by hand. The project then saw trees planted across approximately 200 hectares to protect, restore, and expand rainforest and peatland habitats. Meanwhile, deer fencing was installed at Ardmolich to protect the newly planted native woodlands from overgrazing.

To date, this has been the most ambitious biodiversity enhancement project undertaken by Network Rail in Scotland.

Habitats

Network Rail’s vegetation management work goes hand-in-hand with its efforts to protect the habitats of endangered wildlife across the entire railway estate.

For instance, 18 species of bat are recorded in Britain and most of them use the country’s railway infrastructure for foraging and roosting. The railway provides the perfect refuge, being more densely vegetated and less brightly lit than roads and motorways. Among other initiatives, Network Rail has worked with Chichester local district council since 2021 to create a wildlife corridor around sections of the railway in Chichester, West Sussex. The project has included planting 400 native woodland tree and scrub saplings to diversify the local flora, placing bat boxes in trees to encourage roosting, and converting empty buildings along the line into bat houses.

The discovery of sand lizards near a railway station in the south of England is another example. As Britain’s rarest lizard, Sand Lizards are a conservation priority in England and Wales and are strictly protected under British law. Network Rail first recorded a small number of the creatures on a disused track bed on the lineside around Wareham Station in Dorset in 2013. Since then, it has worked with South Western Railway to transform an old, disused siding known as Old Bay Platform into a suitable environment for the lizards.

The programme has seen the creation of a mosaic of scrub, open grassy areas, and sandy patches which the creatures are known to prefer. The population has since grown, as has the population of Smooth Snakes, Britain’s rarest reptiles. Old Bay Platform is now classified as a ‘railway nature site’.

Furthermore, Network Rail has done much to protect the endangered dormouse, which is known to live along the edge of the railway, mainly in south England and along the Welsh border. The population of dormice has declined by over two-thirds since 2000, according to the People’s Trust for Endangered Species (PTES), but new habitats are currently being created in two fields on the outskirts of Okehampton, next to the Dartmoor line. Native trees and vegetation, including hazel, hawthorn and oak trees, brambles, and honeysuckle, also being planted to create a biodiverse habitat.

Technology

This is but one project underway to protect this species. Since late 2023, Network Rail ecologists have worked with the Zoological Society of London and tech-giant Google to monitor their numbers on lineside land. Camera traps and audio sensors have been placed with a particular focus on a site near Cowden in Kent. Monitoring equipment has also been placed in woodland near Calke Abbey in Derbyshire.

The equipment gathered images, videos, and audio recordings and the data was stored and analysed on GoogleCloud. It is now being used to develop artificial intelligence and machine learning patterns to identify dormouse presence remotely.

Indeed, technology is crucial tool in the mission to boost biodiversity along the lineside. One of Network Rail’s partners, the UK Centre for Ecology & Hydrology (UKCEH), has recently used images from satellites and aircraft to produce a detailed national map of all the habitats found alongside the railway. UKCEH has combined its information with millions of records of species to predict what animals and plants are likely to live in habitats near the railway. This data will ensure rail workers and contractors are aware of the possible presence of rare species when carrying out vegetation management. It will also inform Network Rail’s conservation measures to increase biodiversity and provide a baseline for monitoring future trends in biodiversity.

Balance

However, while encouraging and safeguarding biodiversity is a major concern, Network Rail’s first priorities are the passengers using its infrastructure and the workers maintaining it. Its duty is to remove trees and vegetation that could be dangerous or would impair the reliability of rail services.

Areas of vegetation must be cleared to enable trackside teams to examine or repair earthworks and structures, or as part of larger programmes of work such as electrification. Certain species such as poplar and sycamore must be cut back or removed to reduce the problems caused by leaves on the line. Additionally, the use of pesticides is essential to control weed growth which may otherwise hinder staff access or engulf track and train systems.

Clearly then, there is a delicate balance to be had when encouraging biodiversity and ensuring safety and reliability, but Network Rail’s programme of works in the last five years appear to be treading that fine line between the needs of society and the environment.

Image credit: Network Rail