The environment of the Severn Estuary is unique and diverse, with many different habitats including wetlands, saltmarsh, sandy shores, rivers, rocky coasts, and biogenic reefs. In fact, the intertidal zone of mudflats, sandbanks, rocky platforms, and saltmarshes is one of the largest in the UK, covering an area of 9,971 ha2. Each winter the intertidal zones of the Severn Estuary host an average of 74,000 birds, which migrate from colder climates. Shelduck, oystercatcher, dunlin and ringed plover scour the muds for food and roosting grounds.
In the Estuary’s waters, fish such as sprat, herring and common goby are found swimming downstream to their spawning grounds. Their larvae will then swim up the Estuary to reach the more sheltered nursery grounds. River fish such as salmon, twaite shad and river lamprey make use of the 600 rivers which drain into the Estuary, that carve out a ‘blue motorway’ for boats, people, and animals alike. The River Severn is the longest river that drains into the Estuary at 180 miles (290 km) long, though many other rivers including the Wye, Usk and Avon also drain into the Estuary.
The nature conservation features of the SAC, SPA and Ramsar are laid out in sections below.
The Severn Estuary is internationally important for its wading birds and wildfowl. The species in this section are all features for which the Severn Estuary is designated as a SSSI, SAC, SPA and Ramsar.
The Severn Estuary and Bristol Channel support one of the most diverse fish assemblages in the UK, with over 110 fish species. There are a wide range of migratory and estuarine species.
The Severn Estuary is the largest example of a coastal plain estuary in the UK, covering an area of almost 74,000 ha. It is unique for its immense tidal range, which affects the physical environment and biological communities.
