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| Humberhead Levels |
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| Habitat: Fen, marsh and swamp (of national significance) |
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Includes vegetation that is fed by ground water, and permanently, seasonally or periodically waterlogged peat, peaty or mineral soils, where grasses do not dominate. Includes emergent and frequently inundated vegetation on peat or mineral soils.
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The peatlands of Thorne, Crowle and Goole Moors and of Hatfield Moors form over 3,000 hectares of wilderness - land which is not tamed for agriculture and provide us with an insight into how the Humberhead Levels Natural Area once looked.
The peat which forms bogs and fens is composed of partially decomposed plants. It accumulates where the site is permanently waterlogged. Many of the bacteria and larger creatures, such as worms, that decompose organic matter cannot survive here and so animal and plant remains are partly preserved. Where solutes are relatively plentiful, due to the mineralogy of the local rocks or soils, fen plants such as reed and tall herbs predominate. Over the course of time, the accumulation of fen peat elevates the surface above the solute- enriched water, making it more dependent on rainfall. At some point in this sequence thegrowing conditions change enough for raised bog plants to take over from those of fen.
Evidence suggests that the development of Thorne Moors commenced with reed fen, but that Hatfield Moors started to accumulate peat when the preceding heathland became increasingly waterlogged. Before this wet period, both had a cover of woodland, the large horizontal trunks exposed where the peat has been removed provide the evidence of this. The field patterns and distribution of peaty soil around these remaining peatlands reveal that a cover of peat was once far more extensive in the Humberhead Levels. As the peat component of the present-day deeply drained soils dries and oxidises, the level of the land falls, and is now significantly below sea level in parts. While kept well in check by farming and pumped drainage systems today, the Moors are an important reminder of conditions which were once far more widespread.
Because of their value as sources of peat for historically animal litter, and now horticulture, most of the lowland raised mires in Britain and western continental Europe have been damaged. The scale of damage varies, but England has very few examples which still retain an original surface. Most are stripped of all but one or two metres of peat, and the edges, which would normally support a type of fen vegetation, have been taken into cultivation. The drainage, stripping of surface, and removal of the edge have affected the way in which water can be retained, so that in many cases the conditions necessary for peat to form are no longer present.
Some of our most severely damaged lowland raised bogs are considered important as our only remaining examples, and as a home to the types of plants and animals they support, some of which are not found anywhere else. Their importance is recognised locally, nationally, and in Europe. A biodiversity costed action plan has been prepared for fen habitats due to their increasing rarity.
The fragmented remains of raised mire and fen give us an indication of what the Natural Area used to be like, when losing your step into a quaking mire meant death and residents crossed the marshes on stilts. What is left is internationally very rare, and in contrast to its bleakness, contains a huge number of plants and animals which are highly specialised to live in this fascinating but harsh environment.
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