Ecology
The Severn Estuary is internationally important for biodiversity. At low tide, large areas of mudflat, salt marsh and coastal floodplain provide feeding grounds for populations of several species of waterbirds.
The Avonmouth and Severnside Enterprise Area and the surrounding areas of coastal floodplain have been, and continue to be, the focus for development. This has reduced the amount of available habitat for wetland birds. To ensure economic development can continue within ASEA without adversely affecting the Severn Estuary, we will provide ecological mitigation in the form of newly created wetland habitat.
We are ensuring that a thriving environment will be established for people and wildlife, to last the rest of this century and beyond.
Protecting and boosting nature
Nationally, coastal wetland habitat is one of the most valuable natural habitats. But it is under threat from rising sea levels because of climate change. The Severn Estuary’s protected status means that we will create new habitat to replace wetland affected by new development within the Enterprise Area.
We will create a minimum of 80 hectares (the equivalent of around 112 football pitches) of new wetland habitat as locations for wildlife to thrive; providing “high-tide roosts” for birds. These new wetland habitats at Northwick and Hallen Marsh have been designed to attract waders and ducks including the European white-fronted goose, shelduck, gadwall, dunlin, redshank, wigeon, teal, pintail, pochard, ringed and grey plover, curlew and whimbrel. Find out more about where we are working in the wetlands here.
We are planting a combined total of two hectares (equivalent to about three football pitches) of native species of trees, including silver birch and hornbeam, and shrubs. These could last for centuries to come.
Creating valuable habitats
As we create the wetlands, we pay careful attention to the needs of these species. For example, wetland birds avoid areas with large trees that could provide roosts for their natural predators. So, we will focus on planting shrubs and wetland grasses to give the birds the habitat they need when the high tide has covered the mud flats where they feed. We will keep tree-planting to areas further away from the wetlands, largely in the area between the new flood defences and Severn Road, northwest of Northwick.
We will create ponds for Great Crested Newts in Northwick Marsh and behind the flood defences near Pilning. We are also using mitigation techniques to minimise the impact of our work on existing species.
We released water voles onto the Hallen Marsh wetland in the spring of 2023 and we're delighted that they have happily settled in . With its ditches and vegetation, the wetlands are the perfect habitat for these brown furry mammals which are amongst the most endangered species in the U.K. Find out more, and watch our video of the water voles arriving at their new home, here.
We have provided a replacement otter holt to ensure otters can continue to use an established commuting route. We will put up over 100 bat boxes across the project area, along with two barn owl nest boxes. One of these barn owl boxes has already been used to successfully raise three chicks.
We will create a network of ponds and areas of shallow water (that dry up in summer) called scrapes. They will attract wetland birds, which will be able to use the scrapes to feed and rest at high tide when the mudflats and saltmarsh in the Severn Estuary are underwater. To create the scrapes we will reprofile the land and work with the natural drainage system to trap rainwater.
We will re-use all the soil dug out for the wetland elsewhere in construction, for example creation of embankments.
Click on our ecology map to find out about how planting and how we are protecting and creating habitats.
Watch this short interview with Nicola Beech - Cabinet Member for Climate, Ecology, Waste and Energy, Bristol City Council.
Making it easier to appreciate nature
We’re creating improved walking routes, making it easier for everyone to enjoy nature and the spectacular views of the Severn Estuary. Read our Frequently Asked Questions or watch our flythrough video for more information.
The flood defence project will provide a huge boost to nature and wildlife by creating 80 ha of new wetland habitats to protect the bird species on the internationally important Severn Estuary and planting hundreds of native trees that will improve the environment for many years to come.
Bristol City Council, Cabinet Member for Climate, Ecology, Waste and Energy.
