Grazing Marsh Research Articles

Impacts of hydrological restoration on lowland river floodplain plant communities

Many lowland floodplain habitats have been disconnected from their rivers by flood defence banks. Removing or lowering these banks can reinstate regular flooding and thus restore these important wetland plant communities. In this study we analyse changes in wetland hydrology and plant community composition following the lowering of flood defence banks at a floodplain of the River Don in the United Kingdom (UK). The aim of the restoration project was to improve the quality of “floodplain grazing marsh” habitat, which is a group of wetland communities that are of conservation interest in the UK. We analyse changes in species richness and community composition over a period of 6 years, and compare the presence of indicator species from the target floodplain grazing marsh plant communities. The lowering of the flood banks increased the frequency of flood events, from an estimated average of 1.7 floods per year to 571 floods per year. The increased flooding significantly increased the proportion of time that the wetland was submerged, and the heterogeneity in hydrological conditions within the floodplain. There were significant differences in composition between the pre-restoration and restored plant communities. Plants with traits for moisture tolerance became more abundant, although the communities did not contain significantly more ‘target’ floodplain grazing marsh species at the end of the study period than prior to restoration. Colonisation by floodplain grazing marsh species may have been limited because environmental conditions were not yet suitable, or because of a shortage of colonising propagules. While the desired target plant community has not been achieved after 5 years, it is encouraging that the community has changed dynamically as a result of hydrological changes, and that moisture-tolerant species have increased in occurrence. Over the next few decades, the restored flood regime may cause further environmental change or colonisation events, thus helping increase the occurrence of desired floodplain grazing marsh indicator species.

Distribution of the tick Dermacentor reticulatus in the United Kingdom.

The recent implication of Dermacentor reticulatus (Ixodida: Ixodidae) in the transmission of canine babesiosis in the U.K. has highlighted the lack of accurate published data on its distribution in this country. This paper aims to collate and appraise historical data for D. reticulatus, to supplement such data with more recent surveillance data and to report on field sampling conducted during 2009-2016. These updated data facilitate better understanding of the current distribution of this tick in the U.K., which will better inform disease risk assessments. There appear to be four known regions of the U.K. in which D. reticulatus currently occurs, including western Wales, North and South Devon, and Essex. The majority of foci are located in coastal sand dunes and maritime grasslands, including grazing marsh. However, more recently the tick has been detected in urban greenspace in Essex. The emergence of this tick as a vector of babesiosis in the U.K. and its recent apparent spread in Essex into urban greenspace highlight the need for continued surveillance and for further research into its status as a vector of human and veterinary pathogens.

A preliminary assessment on the role of abandoned shrimp farms on supporting waterbirds in Pichavaram mangrove, Tamilnadu, Southern India

Asian wetlands are pivotal habitats for numerous globally declining migratory and resident waterbird species. Ironically 80% of the wetlands in East and South East Asia are classified as threatened, with 50% under grave threat. In particular the mangrove wetlands are under serious threat due to large scale conversion for commercial shrimp ponds and sea level rise. So, the impoverishment of natural wetlands has forced waterbirds to find alternative habitats. On the other hand, some recent studies have highlighted the potential role of anthropogenic, artificial and restored habitats such as coastal grazing marshes, salinas and rice fields to be good habitats for waterbirds. The present study was mainly designed to investigate the role of abandoned shrimp ponds near the mangroves supporting the migratory and resident waterbirds in the Kodiyampalayam area of Pichavaram mangroves. The results show that the abandoned aqua ponds support 26 species of waterbirds. Among them, 16 were migrant and three were in the near threatened (NT) category of IUCN. Suggestions were made in order to improve the habitat to attract more number of waterbird species in the near future.

Conserving freshwater biodiversity: The value, status and management of high quality ditch systems

Freshwater biodiversity is globally threatened and while most conservation efforts are focussed on natural and larger freshwater systems such as rivers and lakes, in many lowland agricultural landscapes artificial water bodies including ditches may be equally important as habitats for freshwater species. Ditches occur across the agricultural landscape but in particular, those associated with coastal and floodplain grazing marsh, have high conservation value. The importance of this habitat for rare and threatened species afforded priority status under the UK Biodiversity Action Plan is explored. The characteristics of ditches that have high conservation value are described and a set of targets against which such ditches can be assessed are presented. An analysis of the current condition of Sites of Special Scientific Interest (SSSI) for the wider coastal and floodplain grazing marsh habitat demonstrates the range of pressures affecting these sites and highlights that alongside generic freshwater issues such as eutrophication and non-native species, these sites have a unique set of pressures associated with their ongoing management and the vulnerable location of many sites at the coast. Wider conservation strategies for freshwater biodiversity in lowland landscapes across Europe need to factor in the different management requirements of artificial habitats such as ditches alongside more ambitious restoration projects for natural waterbodies. In low lying coastal areas the threat of coastal squeeze for many important grazing marshes will require a strategic approach to allow upstream migration of important biodiversity.

Metapopulation dynamics and a landscape approach to conservation of lowland water voles (Arvicola amphibius)

Effective conservation management for species that function as metapopulations requires an understanding of population dynamics at the landscape scale. The water vole, Arvicola amphibius, is one such species. Water voles have recently undergone a significant decline in the UK, as a result of habitat loss and predation from the introduced American mink, Neovison vison. Large reed bed and grazing marsh sites can provide refuge habitats for water voles from mink predation, in which case populations within these sites could sustain metapopulations in the surrounding landscape where conditions are less favourable. We carried out a study using a stochastic patch occupancy model to determine the long term viability of water vole metapopulations in the wider landscape around a series of extensive reed bed and grazing marsh sites designated as National Key Sites for water voles. The results of our model simulations show that a large protected core site, or mainland, is essential in maintaining the long term viability of these systems. Our results also show how these metapopulations could be enhanced by increasing patch numbers through habitat creation and/or restoration and suggest what the minimum effective size of created or restored patches should be. The study shows how population modelling can provide insight into some effective practical ways of enhancing the viability of water vole metapopulations at the landscape scale. Furthermore it demonstrates that extensive wetlands are an appropriate focus for water vole conservation measures.

Managing water levels on wet grasslands to improve foraging conditions for breeding northern lapwingVanellus vanellus

Summary 1. The widespread drainage of wetlands and grazing marshes has been one of the main drivers of severe reductions in the number and range of breeding waders across Europe. Wader chicks require wet, invertebrate-rich foraging habitats and most agricultural land is now too dry to support sustainable breeding populations. Recent efforts to re-create wet grasslands and improve wader breeding success have focussed on reinstating wet features, in order to provide foraging habitats for chicks. The success of wet feature installation will therefore depend on whether they provide sufficient invertebrate prey for chicks throughout the pre-fledging period. 2. Techniques for re-creating lowland wet grasslands from arable and pastoral farmland are becoming increasingly well-established, and support from agri-environment initiatives is now available for wet feature installation on grasslands. Here we explore the effect of wet feature provision on invertebrate abundance and the growth rates and body condition of northern lapwing Vanellus vanellus chicks, on grazing marshes in eastern England. 3. Wet features supported more than double the biomass of surface-active invertebrates and a greater abundance of aerial invertebrates than the vegetated grazing marsh. Chick foraging rates were also two to three times higher in wet features than in the grazing marsh, as was the estimated biomass intake per food item. 4. At the start of the breeding season, chick condition was unrelated to wet feature provision but late in the season, when water levels were low, chick body condition was significantly higher in fields with footdrain densities of more than 150 m ha )1 . Chick condition declined with increasing rainfall, and low growth rates and longer pre-fledging periods in 2007 are likely to have resulted from unusually intense and prolonged summer rainfall. 5. Synthesis and applications. The installation of wet features on grasslands provides valuable foraging locations for chicks, particularly later in the season when these features are likely to be the main source of water available. Predicted changes to the seasonality of precipitation at temperate latitudes means that provision of wet features is likely to be increasingly important for maintaining breeding wader populations.

Regional assessment of climate change impacts on coastal and fluvial ecosystems and the scope for adaptation

Ecosystem changes in floodplains could be a major issue during the twenty-first century as designated habitat areas are affected by climate change and floodplain management options. As part of the RegIS project, a Regional Impact Simulator has been developed to investigate these potential changes. This paper presents the methodologies and results of biodiversity metamodels used within the Regional Impact Simulator for two regions of the UK: East Anglia and North West England. Potential impacts and adaptations to future climate and socio-economic scenarios are analysed for three habitat types in floodplains (saltmarsh, coastal grazing marsh and fluvial grazing marsh) and selected species. An important finding is that management choices, which can be linked to socio-economic futures have a greater potential impact on habitat viability than climate change. The choices society makes will therefore be key to protection and conservation of biodiversity. The analyses also show that coastal grazing marsh is the most vulnerable habitat to sea-level rise, although there is a scope for substituting losses with fluvial grazing marsh. These results indicate that these methods provide a useful approach for assessing potential biodiversity changes at the regional scale, including the effect of different policies.

Evolution of a Floodplain Landscape: A Case Study of the Harnham Water Meadows at Salisbury, England

Understanding the evolution of alluvial landscapes requires an appreciation of soils, geology, fluvial geomorphology and climate as well as ecology, history and archaeology. For bedwork water meadows systems, it is antecedent floodplain and channel morphologies that condition layout, yet these considerations are generally overlooked. This paper proposes a speculative developmental sequence for the Harnham water meadows at Salisbury from the late Pleistocene, including the construction of floated water meadows in the mid seventeenth century, on an established grazing marsh. It is argued that the 'island' formed at the split in the River Nadder at the confluence with the Avon (upon which the water meadows are situated) is a consequence of accelerated alluviation and channel pattern adjustment to the imposed sedimentary load. Sediment loading from arable agriculture was subsequently ameliorated by vegetation community establishment leading to stabilised river channel geometries that provide the basis for the present arrangement of channels, meadows and mills.

Integrated environmental interpretation at the Curraghs Wildlife Park, Isle of Man

Curraghs Wildlife Park has been developed adjacent to the Ballaugh Curraghs which is one of the few reinnants of an extensive area of wet grazing marshes. The exhibits and graphics at the Park attempt to relate the problems of world-wide conservation and preservation to environmental developments on the Island. A walkway around 5 ha of the parkland enables visitors to visit areas which, until recently, were not readily accessible and graphics explain about local wildlife which may be seen along the way. In 1989 the indoor exhibit area, the Ark. was refurbished and non exhibits a variety of species from tropical rain forests to local introduced predators.

Applying landscape ecology to conservation biology: Spatially explicit analysis reveals dispersal limits on threatened wetland gastropods

Three gastropods in the UK red data book (RDB) occupy drainage ditches on threatened grazing marshes. Segmentina nitida, Anisus vorticulus and Valvata macrostoma are affected by habitat loss, ditch management and eutrophication, but dispersal and fragmentation effects have also been postulated. We used landscape ecological approaches to examine such effects on these and 17 other gastropods on four English marshes, specifically combining ordination to identify suitable habitat with spatially-explicit analysis of occupancy. Among all gastropods, the occupancy of suitable habitat declined significantly as the distance to the nearest occupied site increased. S. nitida and A. vorticulus were among the species most affected, with median nearest distances from occupied to unoccupied suitable sites significantly greater by 3 − 4 X than distances between occupied sites. V. macrostoma was not limited locally by dispersal, but was absent from three out of four marshes with suitable habitat. Eutrophication (elevated N) had no effects on distances between occupied and unoccupied sites and did not contribute to fragmentation. Although four non-threatened species were apparently also limited by dispersal, only two ( Armiger crista; Gyraulus albus) showed some combination of the dispersal effects, low occupancy of suitable habitat (<50%) and small niche extent that characterized RDB species. While dispersal alone cannot explain unfavourable conservation status in these wetland snails, our data support the hypothesis that limited dispersal between (all species) and within marshes ( S. nitida and A. vorticulus) affect all three RDB snails in their remaining UK range. Action is required to better understand the population and genetic consequences; to better understand dispersal mechanisms; and to evaluate re-introduction and reinforcement as aids to recovery. The latter could double the existing site occupancy.

Importance of management on the distribution and abundance of Staphylinidae (Insecta: Coleoptera) on coastal grazing marshes

A combination of survey/multivariate analysis and field experiment was used to examine the importance of management variables in determining the distribution and abundance of Staphylinidae on coastal grazing marshes. In total 22 fields on three different coastal marshes were surveyed and a number of management-affected habitat parameters measured. A field experiment emulating grazing and fertiliser application was carried out on an unmanaged field. Based on Canonical Correspondence Analysis (CCA), 52% of the variation in species assemblages on surveyed fields could be explained with seven environmental variables, which broadly fell into two categories: physical soil properties and structural vegetation characteristics. The most important factors were soil temperature and vegetation height, followed by soil compaction. Whilst staphylinid communities on the same marsh could be clearly separated based on some management categories (no management versus grazing, grazing versus cutting, grazing intensity), the location of the marsh exerted an additional management-independent effect, complicating comparisons between marshes.

The Vegetation of Artificial Drainage Channels Within Grazing Marshes in the UK: How Does its Composition Correspond with Described Communities?

Large areas of British coastal and riverine floodplains support grazing marsh, a landscape representing an intermediate stage in the reclamation of natural wetlands toward intensive agriculture. Once disregarded for nature conservation, in the late twentieth century it was realised that grazing marshes were significant for wetland birds and invertebrates, as well as the key refuge for aquatic vegetation in lowland Britain. The Centre for Ecology and Hydrology (CEH) surveyed this vegetation, focussing on drainage channels and their banks. In multivariate analysis, vegetation composition was related to channel dimensions, soil type, land use, channel management and the drainage function of the channel. CEH attempted to relate the channel vegetation assemblages to those aquatic and swamp types described within the British National Vegetation Classification and the wider literature. Although we sometimes achieved this aim channels often appeared to contain intimate concatenations of types that could not be simply separated into recognised aquatic and swamp associations. Thus, channel vegetation may be represented either as combinations of described communities or as unique multilayered associations, comparable with woodlands. The degree to which aquatic and swamp elements occur in predictable combinations is discussed. Despite being artificial habitats, drainage channels have intrinsic biodiversity value, meriting recognition within European systems for the protection of biodiversity.

Methods for targeting the restoration of grazing marsh and wet grassland communities at a national, regional and local scale

Grazing marsh has been recognised as a key habitat in the UK, and included within the Biodiversity Action Plan structure. In the present research, the conservation value of extant English grazing marsh and its geographical variation were assessed, and a strategy for targeting restoration of grazing marsh developed. A two-stage approach was taken: Botanical species groups were targeted for restoration, and areas identified where this might be attempted. Those species commonest in the wet grassland biotope were defined and classified into species groups on the basis of (a) their established strategy, habitat requirements and life forms; and (b) their occurrence in described plant communities (National Vegetation Classification – NVC). Areas where restoration was practical were identified using co-occurrence mapping of species from both species groups and NVC communities, and the same method used to identify where marked declines in these groups had occurred since 1950. Using national databases (plants, birds, insects) and information on areas through which restoration schemes might be administered (e.g. the English Nature “Natural Areas”), six ecological attributes were derived enabling sites and areas to be ranked for restoration. Areas were also ranked by the total grazing marsh area they presently contained. Qualitative and quantitative rankings were compared. Ranked Natural Areas were assessed on the basis of the liability to flooding, altitude and land cover. Research identified two philosophies for targeting restoration, focusing either on high-quality areas where success is likely, or on degraded sites where relative gain in biodiversity may be greater.

The microdistribution of three uncommon freshwater gastropods in the drainage ditches of British grazing marshes

Abstract The gastropods Segmentina nitida, Anisus vorticulus and Valvata macrostoma occur in drainage ditches on grazing marshes that are now among the most threatened wetland systems in western Europe. Although each of these species is listed in the UK Red Data Book (RDB) and Biodiversity Action Plan, influences on their distribution are poorly understood. 2. To improve management information, the within‐channel distributions of the three snails were examined in 20 ditches in southeast England. Abundance, vegetation cover and other environmental factors were recorded across the ditch profile near the surface (&lt;0.2m) and at depth (&lt;0.15m from the benthos). 3. All three species were significantly more abundant near the surface than at depth. Below 0.6m, ditches had significantly reduced concentrations of dissolved oxygen (&lt;0.6 mg L−1, &lt;5% saturation), possibly sufficient to limit the occurrence of gastropods dependent wholly or partly on aqueous gas exchange. 4. There were no other systematic variations in abundance between the ditch margins and centre channel. However, across all ditches and samples in the survey, each species' abundance varied significantly with vegetation structure. S. nitida was most numerous where there was least open water and hence most vegetation, V. macrostoma among emergent stands and A. vorticulus in ditches with floating vegetation but few submerged plants. 5. These microdistributional data support large‐scale surveys in illustrating the potential importance of vegetation management for these snails; providing that other requirements are satisfied, ditch management could favour each RDB species by optimizing particular vegetation features. Apparent preferences for vegetation structure rather than particular channel locations suggest that refuges left during ditch clearance could be located anywhere in the ditch. Factors that reduce oxygen concentrations below 1mg L −1, such as eutrophication, might be detrimental. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Modelling actual, reference and equilibrium evaporation from a temperate wet grassland

AbstractActual and reference evaporation from a wet grassland in Southeast England was studied over the spring and summer of 1999 (March to September) through changes in surface wetness. The Penman–Monteith (using resistance values for reference grass surface), equilibrium evaporation and Priestley–Taylor models were compared with output from the Bowen ratio energy balance (BREB) method. On field visits, inundation of the grazing marsh was mapped and surface soil moisture monitored in a regular grid using a capacitance probe. During the study period, the extent of flooding fell from approximately 10% to 0% and the surface soil moisture declined from over 38% to 15%. Daily averaged Bowen ratios displayed large variation but were below unity, indicating that latent energy flux was the dominant energy sink. The Penman–Monteith and equilibrium evaporation models underestimated during periods of surface inundation and overestimated when no surface water was present. Computed values of the Priestley–Taylor parameter α showed daily variability, but α was predictable with surface wetness such an average value of α = 1·25 characterized periods of inundation, and an average values of α = 0·80 represented periods of no surface water. The performance of the models in computing actual evaporation was compared with the BREB using the root‐mean‐square error and index of agreement. The optimal model was the Priestley–Taylor model. Copyright © 2004 John Wiley &amp; Sons, Ltd.

The distribution of three uncommon freshwater gastropods in the drainage ditches of British grazing marshes

Marshland drainage channels (=ditches) in the UK are relicts of a once extensive habitat whose management requires quantitative information on the ecology of marshland organisms. Three freshwater gastropods in the UK Red Data Book (RDB), Segmentina nitida, Anisus vorticulus and Valvata macrostoma, are particularly poorly known, and we examined their macro-distribution across 106 ditches on four grazing marshes in SE England. Distribution reflected natural water quality, vegetation and anthropogenic factors. S. nitida occupied shallow calcareous ditches with dense emergent vegetation while A. vorticulus occupied less calcareous ditches with high plant diversity. Ditches with V. macrostoma were dominated by floating plants and slightly elevated chloride. S. nitida and V. macrostoma were absent from otherwise suitable ditches that had elevated nitrate and nitrite indicating effects from eutrophication. Conservation of these three gastropods at the regional scale requires reductions in catchment fertiliser use and also the protection of enough sites to provide the required range of natural factors (e.g., Cl and Ca). At the marsh scale, we suggest that quasi-traditional and rotational ditch clearance can provide the vegetation dynamics and diverse ditch network to ensure suitable habitat for all three species. Better information is required about dispersal, about the effectiveness of reintroduction, and about the most sensitive methods of ditch management.

Diet of breeding Lapwing Vanellus vanellus and Redshank Tringa totanus on coastal grazing marsh and implications for habitat management

Capsule Management of coastal grazing marshes for these breeding wading birds should prescribe maintaining shallow pools in May and June instead of until the end of April as currently set out in most coastal grazing marsh ESA agri-environment schemes. Aims To determine the range of prey and most important components of the diet of breeding Lapwing and Redshank on coastal grazing marsh throughout the breeding season. Methods Prey were determined from remains in faeces and pellets. The contributions of these prey to the diet were estimated by multiplying selected prey remains by published correction factors and dry weights of intact prey. Results Adult Lapwing and chicks and adult Redshank fed on a wide range of soil, surface-active and aquatic invertebrates. Adult Redshank also fed on estuarine invertebrates. The proportion of aquatic invertebrates in the diet of both species increased as the breeding season progressed, while that of soil invertebrates decreased. Conclusion Aquatic invertebrates in shallow pools can be an important component of the diet of breeding Lapwing and Redshank in May and June, but most management of coastal grazing marsh set out in ESA agri-environment schemes only specifies retaining pools until the end of April. Proximity to estuaries might be important in influencing the suitability of coastal grazing marshes for breeding Redshank.

Re-assessing agrarian policy and practice in local environmental management: the case of beef cattle

There are policy pressures to make agriculture more environmentally sustainable and to give a more local expression to agri-environmental priorities. This paper considers these moves, with particular reference to the beef sector, and speculates on the further policy responses required to facilitate benign local agri-environmental management. The UK beef sector is characterized by its complexity and diversity but four major systems can be identified operating at varying levels of intensity. Of these, suckler herds and grass-rearing systems have long been associated with high natural value forms of agricultural land management. Many of the cherished habitats and landscapes of the UK are dependent upon grazing for their ecological and amenity value. However a combination of the BSE crisis, the strength of sterling and the recent Foot and Mouth epidemic threatens the sustainability of these high nature value grazing systems. The importance of grazing to 50 selected Sites of Special Scientific Interest is highlighted in the paper. Survey work identified a wide range of systems to be particularly vulnerable to changes in profitability in the beef sector, including: coastal grazing marsh, wet acidic grassland/marshland, upland moor and heath, calcareous grassland and neutral grassland. To maintain these systems requires agricultural policy to be more sensitive to local conditions than currently appears to be the case. There is little policy support for beef farmers in a regional context, still less giving special prominence to those farming within particular biotopes. Nor has there been sufficient policy encouragement to markets for traditional and local beef breeds. The continuing pressure for CAP reform offers further opportunity for policies to be devolved to regions and localities.

Modelling potential impacts of climate change on the bioclimatic envelope of species in Britain and Ireland

ABSTRACTAim Climate change has the potential to have significant impacts on the distribution of species and on the composition of habitats. This paper identifies the potential changes in the future distribution of species under the UKCIP98 climate change scenarios, in order that such changes can be taken into account in conservation management.Location The model was applied to Britain and Ireland.Methods A model based on an artificial neural network was used to predict the changing bioclimate envelopes of species in Britain and Ireland. Fifty‐four species representing 15 habitats were modelled.Results The modelled species could be placed into three categories: those losing suitable climate space, those gaining it, and those showing little or no change. When the species were associated with habitats it was found that Arctic–Alpine/montane heath communities were the most sensitive to climate change, followed by pine woodland and beech woodland in southern England. In lowland heath, wet heath, cereal field margins, coastal grazing marsh, drought‐prone acid grassland and calcareous grassland, the species either showed little change or an increase in suitable climate space. The other eight habitats showed a mixed response.Conclusions The species show a variety of responses to climate change and thus their current habitat associations may alter. The uncertain future of some species and habitats is highlighted. Conservation policy and practice will need to be revised in the face of climate change.

Modelling potential impacts of climate change on the bioclimatic envelope of species in Britain and Ireland

Aim: Climate change has the potential to have significant impacts on the distribution of species and on the composition of habitats. This paper identifies the potential changes in the future distribution of species under the UKCIP98 climate change scenarios, in order that such changes can be taken into account in conservation management. Location: The model was applied to Britain and Ireland. Methods: A model based on an artificial neural network was used to predict the changing bioclimate envelopes of species in Britain and Ireland. Fifty-four species representing 15 habitats were modelled. Results: The modelled species could be placed into three categories: those losing suitable climate space, those gaining it, and those showing little or no change. When the species were associated with habitats it was found that Arctic-Alpine/montane heath communities were the most sensitive to climate change, followed by pine woodland and beech woodland in southern England. In lowland heath, wet heath, cereal field margins, coastal grazing marsh, drought-prone acid grassland and calcareous grassland, the species either showed little change or an increase in suitable climate space. The other eight habitats showed a mixed response. Conclusions: The species show a variety of responses to climate change and thus their current habitat associations may alter. The uncertain future of some species and habitats is highlighted. Conservation policy and practice will need to be revised in the face of climate change.