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Biodiversity

A key commitment for the Crossrail project has been to minimise any negative environmental impacts while we build the railway and to take advantage of opportunities to provide environmental mitigation. Our main biodiversity focus has been on wildlife and habitat protection.

Wildlife is supported everywhere across the Elizabeth line, even in the dense, heavily populated urban environment of central London so it was important that Crossrail sought opportunities to provide green spaces wherever possible. The land surrounding our portals, shafts, depots and the surface railway to the east and west provided a greater opportunity, you can learn more about our initiatives below.  

The impacts of constructing the project were assessed as part of Crossrail’s  Environmental Statement. 

During the main construction period, the focus has been on protecting wildlife. For example, wild orchids, reptiles, newts and giant eels were all re-homed from the Stockley Junction area in West London, slow worms were moved from the Old Oak Common worksite and fish rescues were carried out from the docks at Canary Wharf and the Royal Docks at Connaught Tunnel. Biodiversity improvements have also been achieved in some areas as a result of the Crossrail Community Investment Programme which supports the local communities and environment. For example, a new wildlife habitat was created on a section of the River Lea. 

As we reach the final stages of construction, we are also exploring opportunities to encourage greater biodiversity at several locations along the Elizabeth line. 

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Biodiversity Accounting

Although the Department for Environment, Food and Rural Affairs (DEFRA) methodology of accounting for biodiversity was developed after the construction works for Crossrail had started, the project adopted the methodology as a way of describing the loss of biodiversity as a result of the project. The methodology gave Crossrail guidance on proposals for restoring worksites that have been used for construction in order to increase biodiversity value. On the surface sections of the route, where the works are being predominantly undertaken by Network Rail, it is also being used to investigate the potential for off-site compensation. The results of this work are presented in the Crossrail Biodiversity Accounting report available on the Crossrail Learning Legacy. 

The project identified a number of biodiversity initiatives to turn some of the loss into a gain, from reuse of excavated material to green roofs and landscaping. 

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Turning Waste Into Gain

Over 8 million tonnes of excavated material were created as a part of Crossrail’s construction programme. This material was beneficially reused to create new habitats, restore landfills and create a golf course. This map shows the top 10 sites that benefitted from the excavated materials. Material was used in varying quantities - at Pitsea Landfill [9], over 180,000 tonnes of chalk from the tunnels between North Woolwich and Plumstead was used; at Wallasea Island [8] 3 million tonnes of material from the central London tunnels and station construction was used.  

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Wallasea Island

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• Excavated material from Crossrail’s tunnels and stations was used to create a RSPB nature reserve at Wallasea Island, Essex
• 1528 shipments have delivered excavated material to the island
• Nearly 80% of excavated material (on a tonne per km basis) was transported by rail and water, removing approximately 150,000 lorries from London's roads

In a landmark partnership with the Royal Society for the Protection of Birds (RSPB), 3 million tonnes of material excavated from Crossrail’s tunnels and stations has been used to create a flagship wetland nature reserve at Wallasea Island in Essex. It has provided a home for tens of thousands of migratory birds and aims to combat the threats from climate change and coastal flooding. The Crossrail material was used to re-engineer the arable landscape and our construction teams breached the sea walls in 2015 to create the new wetland landscape. 

Water voles inhabit most of Wallasea Island’s main ditch and Soke Dyke systems and as our construction programme at the island included an extensive re-shaping of the existing water courses, the voles needed to be re-homed.

A total of 150 voles were captured through organised ‘trappings’ and relocated under licence. A paper  published  by the Chartered Institute of Ecology and Environmental Management (CIEEM)  provides a summary of a large scale water vole displacement study that was undertaken at the Wallasea Island site in 2013 and 2014 in order to test the effectiveness of natural displacement and live cage trapping. In addition to the voles over 8,200 common lizards and 30 adders have been rehomed as part of the works at Wallasea. 

“The RSPB worked with Crossrail to produce Jubilee Marsh and the seawalls around that. They also dug out some lagoons for us, and that’s where we manage how much water comes in and out, and we can do that depending on what we feel the birds need and the other wildlife. During winter we will shut some of the sea off so that it can freshen up with rainwater and then very early in spring we will let it out. Some of that fresh water will come out and the sticklebacks and other fish follow the freshwater trail back up into the lagoons for the birds to feed on and for the fish lifecycles to complete.” Rachel Fancy, RSPB Site Manager for Wallasea Island, June 2021. 

In both January 2020 and January 2021, the RSPB counted over 30,000 wintering birds on site across the entire reserve. Other winter months regularly have counts of 25,000 or more. These numbers are predominantly made up of a few species – teal, wigeon, grey plover, golden plover, lapwing, dunlin and knot – and about half the birds are found on Jubilee Marsh. 

There have also been good numbers of breeding birds on the island. Over 100 pairs of breeding avocets are found across the reserve, with about one third on Jubilee Marsh. About half of the 2,000 pairs of black-headed gulls and half of their 70 pairs of common terns are found also on the islands in Jubilee Marsh. 

Twenty-five nationally scarce invertebrate species have been found on the reserve along with ten nationally scarce plant species. Five of these plants enjoy the saline and disturbed ground found on the site. 

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Biodiversity In Central London - Green & Brown Roof Systems

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In central London, where construction sites are surrounded by dense urban infrastructure, biodiverse roofs and brown roofs have been integrated into the designs at stations and shafts. The two are different - biodiverse roofs are where seed or plants are introduced into the substrate at the time of construction. A brown roof is where the substrate surface is left to self-vegetate from windblown and bird lime seed dispersal. 

The shaft headhouses have a wildflower turf roof, which is a UK native turf consisting of 41 wildflowers and grasses. The turf naturally produces a bio-diverse habitat supporting birds, mammals, bees, butterflies and other invertebrate species. As part of the C360 Crossrail Contract, when Costain Skanska Joint Venture (CSJV) were reinstating the soft and hard landscaping areas of the Stepney Green shaft, they included an excavation for a pond to be further developed by the London Borough of Tower Hamlets and Stepney City Farm. 

The new Whitechapel Elizabeth line station ticket hall and walkway is topped with a green roof of carbon-cleansing sedum plants, improving both biodiversity and energy efficiency. Further green roof systems are included on the Durward Street and Cambridge Heath shafts and GSM building, also located at Whitechapel.   

At Woolwich, a brown roof sits above the main Elizabeth line station entrance. 

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Planting At Portals, Depots And The Surface Railway

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Soft landscaping has been an important part of the Crossrail projects biodiversity initiatives, including tree planting, grass seeding, living wall installation and shrub planting. 

At Pudding Mill Lane portal, restoration and urban realm works including a green wall, shrub, herb, grass seeding, woodland and street trees were completed by the contractor Morgan Sindall. At Royal Oak portal, Costain, as well as providing replacement ballast areas, planted shrub and grassland, wildflower meadow and trees. At the Ilford and Plumstead depots, shrubs and trees have been planted, and at the Old Oak Common depot bank and woodland enhancement have been completed with native along with landscape creation with wildflower and grass, and tree planting. 

On the surface section, at Stockley Flyover the restoration works included planting by Network Rail of broad-leaved woodland, scrub woodland, marginal vegetation and neutral grassland along with the installation of a pond area. At Acton yard, tree species such as English Oak have been planted and a new species rich grassland has been created.

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Crossrail Learning Legacy

You can learn more about Crossrail's Sustainability initiatives, including our approach to biodiversity at our knowledge sharing site, the Learning Legacy.  

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