Habitats and Species

Intertidal mudflats and sandflats

Intertidal mudflats and sandflats are submerged at high tide and exposed at low tide, when nearly 50% of the Humber's bed is exposed. They are created by thousands of tonnes of rich sediments washing in and out of the estuary with every tide. The Humber's intertidal areas provide a complex and highly productive ecosystem that supports a wide range of habitats and species. These include invertebrates such as marine worms and mollusc's which provide a vital source of food for fish and birds.

Large scale reclamation took place in the Doncaster-Goole area in the 17th century and at Sunk Island from the mid 18th to the beginning of the 20th century. Further land reclamation has taken place since but now compensation must be provided for any unavoidable losses resulting from flood defence or port development. The estuary has been slowly eroding (decrease in land bordering the river) in the outer and middle sections, whilst accretion (increase in land bordering the river) occurs in the inner estuary.

Saltmarsh

Saltmarsh develops when salt-tolerant vegetation colonises intertidal sediments on the middle and upper reaches of intertidal areas where tidal inundation occurs less frequently. Saltmarsh starts with pioneer saltmarsh on the lower shore. Behind the pioneer saltmarsh more stable conditions lead to development of Atlantic salt meadows. The Humber Estuary supports saltmarsh on both its northern and southern banks, (approximately 627ha) although in some places the upper marsh communities have been lost due to "coastal squeeze".

The saltmarshes of the Humber are predominantly ungrazed and provide a habitat for nationally rare wildlife. Coastal squeeze is caused by sea defences that hinder the natural migration of the salt marsh inland, as sea level rises. This is the biggest threat to the remaining saltmarsh on the Humber. Losses from coastal squeeze can be mitigated against, by what is called "managed realignment". This sets back the sea defences to provide land which becomes intertidal where the further natural development of saltmarsh can take place.

Samphire is a pioneer saltmarsh plant that grows on the lower reaches of the saltmarshes where the vegetation is frequently flooded. It also grows on open creek sides and depressions or disturbed areas of upper saltmarsh. Samphire provides an important food source for many species of waterfowl and is also collected locally for the table.

Coastal Lagoons

Coastal lagoons are areas of shallow coastal saltwater of varying salinity, separated from the sea by sandbanks, shingle or, less frequently, rock. They are a rare and threatened habitat supporting a rich variety of unique wildlife such as the starlet sea anemone and tentacled lagoon worm. The invertebrate fauna of the Humber's lagoons includes three nationally scarce species and Humberston Fitties near Cleethorpes is described as the third most important saline lagoon in Britain.

Sand Dunes

Coastal sand dunes develop behind sandy beaches where the surface dries out between high tides. The dry sand is blown landwards and if it is deposited above the high water mark and trapped by obstacles and vegetation a dune system begins to grow. Sand dunes are important systems and demonstrate vegetation succession and coastal physiographic processes. Areas such as Spurn are extremely dynamic and as a result, support declining species such as sea holly. The Humber's sand dunes cover an area of over 200ha. Although the dunes are above highest astronomical tide and therefore outside the European Marine Site boundary, processes occurring within the site will affect them, because they are derived from the sandflats (see above).

Grey Seals

Donna Nook supports one of the largest grey seal breeding colonies in England with hundreds of new pups born every year. Grey seals are amongst the rarest seals in the world and the UK population represents about 40% of the world population and 95% of the EU population. At the start of the 2000 breeding season, Great Britain held 124,000 grey seals with Donna Nook being Britain's most south-easterly breeding colony. The most recent years count (2008), revealed the grey seal pup production at Donna Nook to be 1358.

Birds

The Humber is one of the 10 most important estuaries in Europe for birds. It supports internationally important populations of seven species that are listed in Annex I of the Birds Directive.

These are:

Marsh Harrier
Avocet
Little Tern
Bittern
Hen Harrier
Golden Plover
Bar-tailed Godwit

These species are in danger of extinction, rare or vulnerable, and their habitat is subject to special conservation measures to ensure their survival and reproduction. These Seven species occur on the Humber at levels over 1% of the national population and so meet the Special Protection Area qualifying criteria. The Humber Estuary provides around 150,000 waterfowl with safe feeding and roosting grounds over the winter and during spring and autumn migrations. In summer it supports several important breeding populations of scarce or declining species such as the bittern, marsh harrier and avocet.

Sea and River Lamprey

Lamprey are one of the most primitive of all living vertebrate animals. They have a distinct mouth with no lower jaw, instead it is surrounded by a round sucker-like disc within which the adults have strong, rasping teeth.

Sea lamprey

Sea lamprey the largest and least common of the three lamprey species found in the UK; reaching a length of 120cm and weight of 2.5kg. Sea lamprey are thought to be found over much of the North Atlantic in shallow coastal and deep offshore waters, but they migrate into fresh water to spawn. Sea lamprey spawn on clean gravel. These spawning sites are in the main river tributaries of the Ouse such as the Swale, Ure, Nidd and Wharfe. The larvae (ammocetes) hatch out of the eggs and burrow in silt beds before they metamorphose and migrate downstream into the Humber Estuary and to the sea

River Lamprey

River Lamprey are confined to Western Europe. They migrate from the sea to spawn in many UK rivers. Just like their larger cousins they need clean gravel for spawning and marginal silt for their larvae to burrow into. The larvae spend several years in silt beds before metamorphosing and then migrating downstream into estuaries to feed. After 1-2 years, they stop feeding and migrate upstream to spawn in freshwater. The average length of the river lamprey is around 40cm and, on average, they weigh 60g. River lamprey use the Humber as a migratory passage to and from their spawning and nursery grounds in the River Derwent and the River Ouse. Evidence indicates that lamprey are present in the River Humber throughout the year.