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WETLAND HABITAT DIFFERENTIATION AND SENSITIVITY TO CHEMICAL POLLUTANTS (NON OPEN WATER WETLANDS). November 1994. (2 Vols) Her Majesty’s Inspectorate of Pollution, London. 145 + 110 pp.

DoE Report No: DoE/HMIP/RR/040

Contract Title: Wetland Habitats

DoE Reference: PECD 7/9/692 Sector No: 2.1

Contractor's Reference: RG 16673 BQZD5


This Report summarises a literature study on non-open water wetlands. Wetlands are here described in physiognomic terms such as fen, marsh and bog, and in the detailed categories of the National Vegetation Classification. Wetland vegetation is known in some detail, animal data are more sketchy or lacking. Communities are closely dependent on the physical, chemical and hydrological regimes of the habitat. The more nutrient-poor ones are concentrated in the north and west.

Pollutants are deposited from the air, enter from water (surface- and ground-water) and from direct disposal. In wetlands pollutants may be degraded, stored or pass through, though wetlands are highly efficient at purifying many types of chemicals. Habitats deficient in solutes, like bogs, are the most sensitive to further (polluting) additions of naturally-occurring substances like phosphates, sulphate and metals.

The results of this work will be used in the formulation of Government Policy, but views expressed in this report do not necessarily represent Government Policy.


The literature on pollution and non-open water wetlands is sparse, and much of the information required for H.M.I.P. to develop habitat specific environmental criteria is currently unavailable. That which is available is described and discussed in this Report.

Wetlands may be divided into physiognomic types such as bog, fen, marsh, reedswamp, wet grassland, wet woodland and salt marsh, or into detailed categories such as those of the National Vegetation Classification. These are the smallest easily-distinguished vegetation units, each with its own unique range of physical (including hydrological) and chemical variables. Animal data is more sketchy, or indeed lacking.

In addition to the threats affecting all 'wild' British habitats, wetlands have the additional stress of water loss, most having experienced this over the last half century.

Communities have their own integrity, and are the assessment unit: individual species do not occur in each and every satisfactory example of a community, so there are no good indicator species. Communities are remarkably closely correlated with their nutrient and hydrological, etc., status. They are fragile and vulnerable in this respect, even slight alterations in these factors causing alteration and, where relevant, impairment of communities.

Vegetation types have been tabulated in relation to physical and chemical factors, and, where possible, to their sensitivity in relation to different groups of pollutants.

The occurrence of different wetland types is already known in general terms (e.g. more bog in the highland north and west, more fen in the large lowland flood plains). Detail awaits further surveys.

Pollution is defined as chemical changes, due to man's activities, in flora and fauna. It affects wetlands principally by:

(a) aerial deposition, acting most on solute-low wetlands, such as bogs;

(b) fertiliser and pesticide run-off from agricultural land, acting most on the more nutrient-poor wetlands;

(c) effluent and urban and road run-off pollution, acting most on wetlands receiving flow (above- or below-ground) from watercourses;

(d) the irreversible chemical changes occurring in dried (and disturbed) wetland organic soils, acting most on middle-nutrient fens and organic-rich marshes;

(e) the withdrawal of groundwater from wetlands which developed in equilibrium with this groundwater.



Executive Summary

Quality Assurance

Volume 1

Section 1 Introduction:
the objective and tasks of the contract; defining wetlands; defining high- or good-quality wetlands; defining pollution; data for this contract available in the literature; data for this contract missing from the literature; review of key literature.

Section 2 Task 2:
Secondary wetland habitat types and their occurrence; introduction; the National Vegetation Classification (NVC); wetland distribution; relationship between physiognomic and NVC wetland categories.

Section 3 Task 3:
The floristic and faunistic (macro- and micro-), physical, chemical and hydrological regimes and differences of secondary wetland types; Introduction; algae; micro-organisms; invertebrates; fish; amphibia; birds; mammals; physical, chemical and hydrological regimes related to the National Vegetation Classification; land form, development; hydrology and wetland transects: case studies.

Section 4 Task 4:
Pathways of substances to, within and from wetland habitats, transformations within them, and their function as sinks; introduction; case studies; solutes and soil processes; purification in swamps, fens and marshes; buffer strips; natural wetlands used for pollution disposal; constructed wetlands used for pollution disposal; air pollution, bogs and constructed bogs for pollution disposal; conclusion.

Section 5 Task 5:
The potential sensitivity of the different (secondary) wetland habitats to the impacts of different pollutant groups; introduction; the sensitivity of National Vegetation Classification wetland types to pollution; examples of pollution damage to habitat and vegetation; examples of pollution damage to animals; oil spills and saltmarshes.

Section 6 Task 7:
Final conclusions and recommendations for the protection of wetland habitats in relation to pollution sensitivity, for equal protection; introduction; assessment and biotic receptors - conclusions; conclusion from case studies; pollution sources and sensitive habitats -conclusions; recommendations.



Volume II

Annex 1:
Case study of East Fork Poplar Creek, Tennessee, USA.

Annex 2:
The National Vegetation Classification of wetland communities;
introduction; M Mire communities; S Swamp and tall herb fen communities; W Woodland communities; MG Mesotrophic grassland communities; saltmarsh communities.

Annex 3:
Birds of wetlands in England and Wales; introduction; birds of different habitats.

Annex 4:
Phragmites australis, pollution and nutrients.

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