How London’s excavated soil helped create a thriving wildlife haven in Essex

A large nature reserve created using soil dug up from the Elizabeth line tunnels under London has proven so successful that it is to be substantially enlarged.

Wallasea Island at high tide (c) RSPB

The 740-hectare nature reserve in Essex, Wallasea Island, was started in 2006 with a small project to convert farmland into mudflats and salt marsh.

In 2012, when the Crossrail project was looking for somewhere to put all the soil it was about to dig up from under London, the Wallasea Island project was also planning a major expansion of the salt marshes and needed tons of soil to raise the farmland above sea level and create a network of slow-lying ridges to create seawater lagoons on the former farmland.

Some 3.2 million tonnes of London soil was taken by train to Gravesend and then by barges to Wallasea Island, where it was used to create the new nature reserve. In 2015, the sea wall that had protected the low-lying land for farmers was breached, flooding the farmland.

Since then, wildlife has returned en masse.

Spoonbills sift through the saline lagoons in spring and summer, and Black-tailed Godwits use the shallow pools to refuel on their migrations. The grassland on the reserve is managed for hunting birds of prey in winter, such as Short-eared Owls and Hen Harriers, while in summer, it becomes a habitat for Adders and rare invertebrates, such as the Shrill Carder Bee and Black Oil Beetle.

In 2023, the reserve broke its own records when a total of 38,000 birds were recorded on Wallasea Island in December’s monthly Wetland Bird Surveys.

Building on that, the RSPB, which manages the site, has acquired four more fields, totalling 100 hectares of farmland next to the nature reserve.

The expansion will be used for the nature reserve’s first freshwater pool, which they hope will attract Red-listed wading birds. Creating a freshwater pool will also offer feeding opportunities to ducks passing through for a pitstop on migration and the species that spend winter on our shores, like Teals, Shovelers and Wigeons.

Meanwhile, the other three fields will be developed into a mosaic of grassland and scrub, with additional wet areas, to provide extra bird habitat, including breeding Corn Buntings. Wallasea Island is already a stronghold for this lowland farmland bird, which has seen dramatic population declines across the UK.

The newly acquired land for the expansion will be grazed by roaming livestock using ‘fenceless grazing’ technology to create a diverse habitat, attracting a range of species. The use of cattle, rather than intensive human intervention, is part of the vision for Wallasea Island to act as a wild landscape.

The project also created about eight miles of coastal walks which are now open to the public.

If you want to visit and see where London’s soil dug up by Crossrail machines is now providing a home for wildlife, the easiest public transport access would be to take a Greater Anglia train to Burnham-on-Crouch and then catch the ferry to the nature reserve. Note that the ferry only operates between April and September.

Although Crossrail’s involvement was only one part of a much larger project, the success of the Wallasea Island nature reserve is rightly part of its legacy.

Updated 21st Jan – removed reference to cycle routes.