Key Features
Intertidal mudflats & 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. 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, including invertebrates such as marine worms and mollusc's which in turn provide a ivital 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. There has been some land claim since but now compensation must be provided for any unavoidable losses resulting from flood defence or port works. The estuary has been slowly eroding in the outer and middle sections, whilst accretion occurs in the inner estuary.
Saltmarsh 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 e.g. 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 dunes develop behind a sandy beach with a surface that dries out between high tides. The dry sand is blown landwards and if deposited above the high water mark and trapped by obstacles and vegetation, the dune system begins to grow. Sand dunes are important systems illustrating 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, particularly as the sandflats (see above) are their source of material.
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. 
Birds
The Humber is one of the 10 most important estuaries in Europe for birds. It supports internationally important populations of seven waterfowl species that are listed in Annex I of the Birds Directive. 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. Seven species occur on the Humber at levels over 1% of the national population and so meet the SPA qualifying criteria.It provides 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 pr declining species such as the bittern, marsh harrier and avocet.
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. where as average length of the river lamprey is around 40cm with a weight of some 60g. River lamprey use the Humber as a migratory passage to and from their spawning and nursery grounds in the River Derwent and Ouse. Data from power station fish impingement assessments indicate that they are present in the Humber throughout the year.