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Nature Reserves: ​How Elizabeth Line Excavations Created a Record-Breaking Haven for Birds

5 December 2025
Special Feature By James Hamilton
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Knot are thriving. Image by Andy Hay (rspb-images.com)

​What happens when three million tonnes of London clay meet a windswept island on the Essex coast? If you’re a birdwatcher, the answer is pure magic.

Last winter, nearly 40,000 birds — a record-breaking number — flocked to Jubilee Marsh on the RSPB’s Wallasea Island nature reserve. It’s hard to believe that just over a decade ago, this thriving wetland was little more than a construction site in waiting.

A Modern Marsh Built From a Mega-Project

​Wallasea Island had been locked away from the sea for centuries. But when the RSPB took it on in the mid-2000s, the dream was to restore it to a wild, salt-kissed haven once again. Enter Crossrail (now the Elizabeth line).

As London tunneled its newest high-speed railway, millions of tonnes of excavated soil needed a home. Instead of disposal, it became the foundation, literally, for a conservation triumph. The soil was shipped to Essex and used to sculpt wetlands: lagoons, saltmarshes, island clusters, and intricate channels designed with wildlife in mind.
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Then came the moment of transformation. In July 2015, portions of the seawall were removed, and for the first time in 400 years, the tide surged back into Wallasea. The island exhaled, rewetting its ancient landscape.

A Home for Thousands — And Growing

Fast forward ten years, and Jubilee Marsh is humming with life:
  • 800 Avocets — a flagship species for the site
  • 10,000+ Knot
  • Nearly 3,000 Grey Plovers and Bar-tailed Godwits
  • And an astonishing 39,000 overwintering birds last year

For many bird species, these wetlands offer precious feeding grounds and safe places to nest or rest during long migrations. For birdwatchers, it’s become one of the most exciting sites on England’s east coast—a living example of what happens when conservation and engineering work hand in wing.

A Potential World Heritage Treasure

​These wetlands are so ecologically important that England’s east coast, from the Thames Estuary to Lincolnshire, now sits on the UK’s Tentative List for UNESCO World Heritage status. If accepted, these habitats would join the ranks of the Galapagos Islands and the Great Barrier Reef.

“An Almost Unbelievable Transformation”

​RSPB staff still marvel at what the site has become. “When I first started working at Wallasea Island it looked an awful lot like a construction site,” says Rachael Fancy, Site Manager. “But ten years on… there’s just thousands and thousands of birds who now use it as a refuge, shelter, and nursery for their chicks.”

And from TfL’s perspective, the transformation reinforces the idea that infrastructure can support nature, not just disrupt it. As Isabel Coman of TfL puts it, Wallasea is “a lasting, positive contribution” born from the creation of the Elizabeth line, now the UK’s busiest railway.

Visit the reserve 👉 rspb.org.uk/days-out/reserves/wallasea-island
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Rejuvenated wetlands. Image by Ben Hall (rspb-images.com)
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