RSPB Wallasea Island: Turning farmland into a wetland for birds

Every day, hundreds of thousands of people travel along the Elizabeth line. As these commuters, tourists and visitors make their way beneath London, they probably aren’t aware that they’ve helped another set of travellers – birds.

More than three million tonnes of soil excavated during the construction of the line’s tunnels was taken to the Royal Society for the Protection of Birds’ (RSPB) reserve on Wallasea Island, where it was used to make an enormous nature reserve as part of the UK’s largest coastal habitat creation project.

What was once farmland is now being reclaimed by nature, helping to buffer the UK’s coastline against erosion and rising sea levels.

The island’s mud is now full of shellfish and worms, providing prime feeding grounds for migratory birds. Rachel Fancy, who manages the RSPB’s nature reserve on Wallasea, says that it’s already a hit with our feathered friends, with record numbers of birds recorded at the site this winter.

“Thanks to our efforts, and the sea doing its bit, this site is now an excellent feeding and wintering habitat,” Rachel says. “There have been high numbers of birds like red knot, grey plover and avocets at Wallasea, which has been great to see.”

But how did this project come together? To find out, we need to go back to the beginning.

Coastal wetlands: Crucial for nature

A long time ago, Wallasea Island formed part of a wider network of coastal wetlands stretching along the coast of the UK. These ecosystems, including habitats like salt marshes and mudflats, are estimated to have once covered around 4% of England and Wales.

As well as providing food and shelter for birds and young fish, these wetlands have wider impacts on the planet. They absorb large amounts of carbon dioxide as they grow, burying it in the mud. Meanwhile, they slow down waves hitting the coast, reducing the effects of erosion.

Yet, these benefits often go unrecognised. Around 90% of England’s wetlands have been lost in the past 500 years as areas were drained and converted to other uses. This has put coastal wildlife under pressure and contributed to the UK becoming one of the most nature-depleted countries in the world.

Even in the 1990s, areas of coastal wetland were still being drained for development. The introduction of new laws, however, meant that when two sites in eastern England were used for port expansion, parts of Wallasea were selected to offset the losses.

Turning the tide for UK wetlands

The initial work to restore the island’s salt marshes and mudflats in the mid-2000s drew the attention of the RSPB. They were looking for a coastal site for a new reserve, and when a former farm on the island came up for sale, they made a deal to buy the land.

Their aim was to create a nature reserve that would provide valuable habitat for wildlife for years to come. This involved a process known as managed realignment, where sea walls are moved further inland to allow new areas of salt marsh and mudflats to develop.

However, the process isn’t quite as easy as it sounds.

“Creating this habitat isn’t just a case of knocking down the sea walls,” Rachel says. “Our modelling found that breaching the wall on its own would bring an extra 11 million cubic metres worth of water onto the site on each spring tide, which would have flooded the entire area.”

“Not only that, but Wallasea is a special case due to its position between the River Crouch and River Roach. Just letting the water in would have had quite catastrophic effects on fisheries, flood defences and other coastal habitats in the surrounding area.”

However, modelling revealed that allowing just up to two million cubic metres of water onto the site, enough to fill London’s Millennium Dome, wouldn’t affect the wider estuary but would allow the wetlands to start developing. To achieve this vast amounts of earth would be needed to raise the land before breaching the existing seawalls.

Fortunately, over in London, millions of tonnes of soil would soon need somewhere to go.

Wetland restoration

Given the go-ahead in 2008, the Crossrail Project aimed to link up existing railway lines to the east of London to those to the west by building the Elizabeth line. At one point it was the largest construction project in Europe, creating 21 kilometres of new tunnels.

In total, this meant moving around seven million tonnes of soil out from under the capital. While it was originally destined for landfill sites around the UK, plans changed when Crossrail learned of the RSPB’s vision, and nearly half of it was sent to Wallasea instead.

Getting the soil to the Essex island, which lies more than 35 kilometres beyond the end of the Elizabeth line in Shenfield, was no easy task. It took a mammoth operation, involving boats, trains and trucks, to get the earth out to the new reserve.

Rachel began working on the island midway through this transformation. She describes the island as looking like a “moonscape” when she arrived, with an enormous conveyor system and dumper trucks shifting the incoming soil around.

“The first job was building up a new seawall behind the old one, at the top of a gradual slope made from the transported soil,” she recalls. “This means that, even as climate change causes sea levels to rise, we’ll be able to keep a full range of habitats from grassland to salt marsh and mudflats.”

“We then sculpted the rest of the area with the remaining Crossrail material, building a series of islands and lagoons. This gave the birds areas to roost beyond the tides when they weren’t feeding on the mudflats.”

Eventually, in July 2015, it was time to let the sea come back to Wallasea. Three breaches were made in the old sea wall during low tide, and as it rose, seawater washed over parts of the island it hadn’t touched in more than 400 years.

It’s now been almost a decade since the forces of nature began restoring the new area of the reserve, named Jubilee Marsh. Wallasea is now well on its way from farmland to wetland.

A hub for migratory birds

The changes to Wallasea were slow at first. As waves lapped the shores of the former farm, the seawater washed in new sediments and seeds, building up the mudflats and salt marshes that are so important to coastal biodiversity.

Beneath the surface, the land was starting to recover too. Cockles and ragworms were among the animals drawn to the mudflats, which in turn brought in the birds that feed on them. As a result, there were more than 12,000 birds wintering at the site within just two years. Within nine years, there were 38,000.

Malcolm Ausden, a Principal Ecologist at the RSPB, says that the site is continuing to develop as Jubilee Marsh reaches its first decade.

“Numbers of birds using Wallasea are still increasing as the habitat continues to develop and more birds discover the site. We’re also continuing to make small tweaks to improve the habitat for wildlife, such as creating more islands for birds to nest and roost on.”

RSPB Wallasea Island is an increasingly popular stopover point for birds as they migrate from as far away as Sub-Saharan Africa to breeding grounds in the Arctic along the East Atlantic flyway. The island’s importance has been recognised nationally and internationally, forming part of a proposed UNESCO World Heritage Site.

“The UK is a vital part of this wider system for many different migratory birds,” Malcolm adds. “Its large tidal range and long coastline provide a lot of intertidal habitat for birds to stop off and feed during their epic journeys.”

“This makes the country an amazing meeting point for birds that breed across the northern hemisphere, including brent geese, bar-tailed godwits and dunlins.”

Searching for the next Wallasea Island

As Wallasea continues to mature as a reserve, the RSPB is on the lookout for new opportunities for large-scale conservation projects.

“We’re desperate to do ‘another Wallasea’ as it’s often referred to,” Malcolm says. “We’re doing a lot of other coastal restoration work at the moment, but nothing on quite this scale.”

“We’d love to work with other major infrastructure projects to make our planet better for both people and nature.”