Coastal Squeeze

The coast is a dynamic environment, continually changing. As sea levels rise, coastal habitats naturally need to migrate/shift landwards to adapt to the changing conditions. But when man-made constructions such as sea walls impede their progress, the habitats are squeezed, resulting in the loss of valuable life sustaining ecosystems. These include saltmarsh, intertidal mudflats, beaches, sand dunes and lagoons. This effect is known as coastal squeeze.

In some areas of the coast where rates of sea level rise are increasing more rapidly, and/or sediment supply is lower, so less availability of sands, muds and gravels that help nourish those coastal habitats, the habitats are more vulnerable to coastal squeeze.

Along the south and southeast coast of the UK, these types of conditions are more prevalent. Sea level rise is predicted to increase at a faster pace and in areas such as Chichester Harbour, hard sea defences also hinder the natural supply of sediment, so critical for the stabilisation of healthy coastal habitats.

How is coastal squeeze impacting the natural environment in Chichester Harbour?

Natural England estimates that Chichester Harbour has lost 58% of the saltmarsh habitat since 1946 and that it continues to lose 2.54ha of saltmarsh per year (the size of 3 football pitches). Coastal squeeze is a significant factor contributing to this loss and its impact is predicted to increase as sea levels rise at an accelerating pace.

These images of Chichester Harbour show the contrast between a natural coastline, and a coastline defended by a hard sea defence which is contributing to coastal squeeze. If we wish to maintain and improve the quality, extent and beauty of the natural Harbour landscape, we need to address the widespread occurrence around the Harbour of existing sights like those shown in the second photograph.

If we wish to continue to enjoy watching the birds, we need intertidal feeding areas, roosting and nesting sites. If we relentlessly maintain hard defences, saltmarshes will continue to disappear as they have nowhere to go. Sea level rise will increase intertidal habitat loss and where their vital habitat disappears, so do the birds.

For those who enjoy the Harbour’s coastal walks, as intertidal habitats disappear, enjoyment of the seaward landscape will become increasingly restricted to shrinking mudflats, water and boats. If we always fight to maintain the coastal footpath along its current route, the view of the landscape we enjoy will continue to deteriorate in this way. Allowing the footpath to gradually move landwards still maintains a footpath and access to the Harbour, but also enables the intertidal habitat to migrate landwards, helping to protect the views we enjoy today.

We all (people, plants and animals) want a Harbour in the future that provides us with the same or better experience that we enjoy today. We are witnessing the decline and habitat loss now. We need to find ways to address the pressures of coastal squeeze, work with natural coastal change and help reverse this declining trend.

Further information on coastal squeeze can be found in the report published by the Flood and Coastal Erosion Risk Management Research and Development programme and Environment Agency.