Estuarine Habitats

This plan covers the Humber Estuary and associated habitats, including mudflats, saltmarsh and reedbeds. The Estuary makes up over 4% of Kingston upon Hull, therefore estuarine habitats are particularly important.

The Estuary itself is home to many species including Grey Seals, and Lamprey (a primitive type of fish); both Sea Lampreys (Petromyzon marinus) and River Lampreys (Lampetra fluviatilis) are found in the Humber. Other fish such Flounder (Platichthys flesus) move up into the Estuary to feed, and it also provides important nurseries for North Sea fish populations, including Codling.

Over one third of the Humber Estuary is exposed as mud or sand flats at low-tide. These intertidal flats are of national and international importance for wildlife. Mudflats are attractive habitats for invertebrates such as burrow-dwelling worms and bivalves. The large numbers of invertebrates which occur on the flats support fish and are winter food for wading birds from both Britain and Europe, including Dunlin (Calidris alpina), Redshank (Tringa totanus) and Ringed Plover (Charadrius hiaticula).

Saltmarsh occurs on sheltered parts of the Estuary. It can be thought of as a habitat between fully marine and land conditions. Saltmarsh vegetation consists of a limited number of salt-loving species that are adapted to regular covering by the tides. Saltmarsh habitats are probably best known in conservation terms for their breeding birds, as feeding areas for wintering wildfowl and waders and as high-water roosting sites for large numbers of gulls, terns, waders and wildfowl. However, saltmarshes are also home to many other species including molluscs, for example the Dun Sentinel (Assiminea grayana) and Mouse-eared Snail (Ovatella myosotis) and many insect species. The Humber Estuary supports extensive areas of Common Reed (Phragmites australis). This habitat supports a variety of birds such as Reed Warbler (Acrocephalus scirpaceus), and Sedge Warbler (Acrocephalus schoenobaenus).

Both mudflats and other intertidal areas are very important for coastal defence. They break-up wave energy, so reduce the risk of eroding saltmarshes, damaging coastal defences and flooding low-lying land. Saltmarshes are important in defending the land against erosion and they also trap sediments and pollutants.

Current Status

The total UK estuarine resource has been estimated as about 588,000 hectares of which 55% is intertidal area, mostly mud and sandflats with a lesser amount of saltmarsh. The UK has about 15% of the north-west European estuarine habitat. The mudflats of the Humber exposed at low-tide cover an area of 1300 hectares, representing 4.5% of the British resource.

The southern boundary of Hull, which runs from west of Hessle to Salt End, stretches well into the River Humber, and includes 314 hectares of water, about 4.4 % of the City area. Within the Hull boundary there are extensive areas of mud flat, and some important areas of reedbed and saltmarsh exist west of St Andrew's Dock.

Current Factors Affecting the Habitat

The Humber and its wildlife face a number of serious threats, ranging from long-term, estuary-wide threats such as sea level rise and industrial and port related development, through to much more localised problems, such as recreational disturbance at sensitive sites.

• Sea level rise is the greatest threat to the Estuary's wildlife. Average sea levels are rising by about 6 mm per year in the Estuary. The Humber is held back for the most part by an extensive fixed line of flood defences. As the sea level rises, the intertidal areas will gradually decrease in a process known as 'coastal squeeze'. Estimates suggest that hundreds of hectares of intertidal habitat are likely to be lost in this way over the next twenty years, leading to significant losses of feeding and roosting habitat for shore birds, which may lead to a decline in their wintering, passage and breeding numbers on the Estuary. In Hull, this may lead to loss of large areas of mudflat and complete loss of saltmarsh habitat, with no means of recreating it within the city boundary because of the flood defence line.
  
  
• Pollution from agriculture, industry and urban areas is still a threat to the Estuary's wildlife, although water quality has been improving for many years.
  
  
• The Humber is an important national location for many industries. Infrastructure development, such as power station cooling systems, gas and chemical pipelines and electricity cables across the intertidal area, can have significant impacts on the Estuary's wildlife. Port development may need direct access to deep-water channels, which can result in direct loss of habitat.
  
  
• Unregulated recreational activity can have a severe impact on wildlife, mainly through disturbance. In the most sensitive areas, such as high-tide wader roosts, even normally harmless activities such as dog walking, can force birds to leave traditional sites.
  
  
• Dredging for navigation or aggregates may have an important effect upon the animal and plant life of the sediment, and sediment supply and transport.

Current action

Legal Status

Some areas of the Humber Estuary are designated as Special Protection Areas (SPA); this is the European designation for the protection of specific species of bird. The extension of this designation to the whole of the Humber is being considered. The whole of the Humber is recommended as a Special Area of Conservation (SAC), the European designation for the protection of specific habitats and species, giving it the status of a 'European Marine Site'. The United Kingdom is required to set and meet conservation objectives for European Marine Sites. The whole of the Humber is also proposed as a Site of Special Scientific Interest.

Management, Research and Guidance

A number of local, statutory and public bodies have created the 'Humber Management Scheme' to meet the conservation objectives required for the Humber as a European Marine Site. These bodies are known as the 'Relevant Authorities'. The Humber Management Scheme aims to maintain the favourable condition of the habitats on the Humber Estuary and make sure that suitable management is carried out.

The Environment Agency is responsible for developing Shoreline Management Plans (SMPs). The main concern of SMPs is flood and coast protection; the importance of mudflats in protecting low lying coastal features is recognised. The SMP proposes managed retreat of some limited defences as a way of creating extra capacity in the Humber. This has the added advantage of creating additional habitat.

The Environment Agency also carry out intertidal biological sampling to test water quality, two sampling points are within the Hull boundary (Alexandra Dock and St Andrew's Quay). The EA collect seaweed (Fucus) from these two sites, which is then analysed for pesticides and heavy metals as part of their bioaccumulation survey.

Monthly high-tide counts of waterfowl are carried out on the Humber as part of the Wetland Bird Survey (WeBS). This is a national scheme run by the BTO, RSPB, JNCC and WWT. English Nature and the RSPB carry out monthly low-tide waterfowl counts throughout the Estuary. Other organisations, such as BP, also contribute by collecting data and keeping records.

The UK Biodiversity Steering Group has produced a Habitat Statement for estuaries, which recommends that the conservation direction should be to maintain and enhance the extent and quality of estuarine habitats in the UK, including the full diversity of estuarine communities.

The UK Biodiversity Steering Group has produced a Habitat Action Plan for mudflats. The Plan aims to maintain at least the present extent and regional distribution of the UK's mudflats; create and restore enough intertidal area over the next 50 years to offset predicted losses to rising sea level in the same period; and restore estuarine water quality to ensure that existing mudflats fulfil their important ecological and conservation role. A national Habitat Action Plan has also been produced for coastal saltmarsh. The overall objectives of this plan are to offset the current losses due to coastal squeeze and erosion, to maintain the existing extent of saltmarsh habitat, and to restore the area of saltmarsh to 1992 levels.

Action Plan Aims

1. To maintain the quality of the existing estuary mudflats in terms of community and species diversity and restore the nature conservation interest through appropriate management.
2. To continue sampling to test the water quality and levels of heavy metals and pesticides.
3. To continue monitoring of bird populations on the Estuary.
4. To continue involvement in production of an Estuary-wide Action Plan.
   

What we are going to do

What We Can All Do

• Report any unusual animal sightings, especially birds to the Partnership.
  
• Report any suspected pollution incidents to the Environment Agency.
  
• Report any sightings of injured/dead birds or other animals to the Environment Agency or Environmental Health at Hull City Council.
   

Links With Other Action Plans

Freshwater Habitats are closely linked with this plan. Estuarine habitats are essential for Saltmarsh Snails and Reed Buntings.

References

Davidson, N.C. et al. (1991) Nature Conservation and Estuaries in Great Britain. JNCC, Peterborough.

Humber Estuary Management Strategy (1997)

The Humber Estuary LBAP Steering Group (1999) Humber Estuary Local Biodiversity Action Plan Draft. Humber Management Strategy.

UK Biodiversity Steering Group/English Nature (1998-9) Tranche 2 Action Plans, Volume V: Maritime Species and Habitats. English Nature, Peterborough.

UK Biodiversity Steering Group (1995) The UK Biodiversity Steering Group Report Volume 2: Action Plans. UKBSG.