Coastal Grazing Marsh Research Articles

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.

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.

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.

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.

The impact of livestock on Lapwing Vanellus vanellus breeding densities and performance on coastal grazing marsh

Capsule Even at very low stocking densities, livestock reduce breeding densities of adult Lapwings and increase the risk of nest loss due to predation. Aims To assess the effects of livestock on Lapwings breeding on coastal grazing marshes. Methods Densities of breeding adults, clutch sizes, laying dates, incubation schedules, clutch and chick survival were compared between marshes grazed at low stocking densities (0.2–0.51 livestock units/ha) and marshes where livestock had been excluded. Repeated measurements of sward heights were also made. Results. Breeding densities in 1995 and 1997, but not 1996, were negatively correlated with the presence of livestock. Though few nests were trampled, livestock disrupted incubation schedules and increased the risk of nest predation. Clutches were smaller on grazed marshes than on ungrazed marshes, while more clutches were also laid later on grazed marshes. Grazed swards remained shorter, and more suitable for nesting, longer than ungrazed swards but clutches laid later in the season were more likely to be predated. Conclusion The exclusion of livestock from selected areas to increase the nesting success of lapwings is a desirable option on coastal grazing marshes where the rate of grass growth is slow in spring. Grazing regimes are suggested that would maintain relatively short swards, provide refuge to Lapwings from livestock during the peak nesting period, and allow grazers to exploit all of their marshes.

Management of coastal grazing marshes for breeding waders: the importance of surface topography and wetness

Coastal grazing marshes are amongst the most threatened habitats in the UK. Those in the North Kent Marshes ESA in south-east England support large breeding populations of lapwing ( Vanellus vanellus) and redshank ( Tringa totanus). Habitat preferences, feeding rates and nest site selection by lapwing and redshank were investigated to determine the importance of rills (relict saltmarsh drainage channels) and surface wetness. Studies showed that lapwing chicks and redshank preferred to feed in rills, where their feeding rates were higher than those on open turf. Feeding rates were also higher in wet rills than in dry ones. Lapwings but not redshank tended to nest closer to rills than would have been expected by chance. These findings identify a behavioural link for the relationship between the birds' distribution, rill availability and wetness. The study also showed that the settling densities of both species were highest in marshes containing rills with many branches. It is, therefore, possible to attract breeding lapwing and redshank by flooding rills during April and May to create water margin habitat for feeding. As this approach does not appear to result in extensive sward death, it is a practical alternative to extensive flooding on grazing marshes that are managed for breeding waders and livestock production.

Habitat models of bird species' distribution: an aid to the management of coastal grazing marshes

1. Coastal grazing marshes comprise an important habitat for wetland biota but are threatened by agricultural intensification and conversion to arable farmland. In Britain, the Environmentally Sensitive Area (ESA) scheme addresses these problems by providing financial incentives to farmers to retain their grazing marshes, and to follow conservation management prescriptions.2. A modelling approach was used to aid the development of management prescriptions for ground‐nesting birds in the North Kent Marshes ESA. This ESA contains the largest area of coastal grazing marsh remaining in England and Wales (c. 6500 ha) and supports nationally important breeding populations of lapwingVanellus vanellusand redshankTringa totanus.3. Counts of ground‐nesting birds, and assessments of sward structure, surface topography and wetness, landscape structure and sources of human disturbance were made in 1995 and again in 1996, on 19 land‐holdings with a combined area ofc. 3000 ha. The land‐holdings varied from nature reserves at one extreme to an intensive dairy farm at the other.4. Models of relationship between the presence or absence of ground‐nesting birds and the grazing marsh habitat in each ofc. 430 marshes were constructed using a generalized linear mixed modelling (GLMM) method. This is an extension to the conventional logistic regression approach, in which a random term is used to model differences in the proportion of marshes occupied on different land‐holdings.5. The combined species models predicted that the probability of marshes being occupied by at least one ground‐nesting species increased concomitantly with the complexity of the grass sward and surface topography but decreased in the presence of hedgerows, roads and power lines.6. Models were also prepared for each of the 10 most widespread species, including lapwing and redshank. Their composition differed between species. Variables describing the sward were included in models for five species: heterogeneity of sward height tended to be more important than mean sward height. Surface topography and wetness were important for waders and wildfowl but not for other species. Effects of boundaries, proximity to roads and power lines were included in some models and were negative in all cases.7. Binomial GLMMs are useful for investigating habitat factors that affect the distribution of birds at two nested spatial scales, in this case fields (marshes) grouped within farms. Models of the type presented in this paper provide a framework for targeting of conservation management prescriptions for ground‐nesting birds at the field scale on the North Kent Marshes ESA and on lowland wet grassland elsewhere in Europe.

Habitat use by Lapwings and Golden Plovers in a largely arable landscape

Numbers and habitat preferences of breeding Lapwings and of wintering Lapwings and Golden Plovers were studied over three years in a largely arable district of northeast Essex. There were 49–54 pairs of breeding Lapwings over the period 1994–96, using 6–9 sites, with 69–83% of the total in coastal grazing marshes. The majority of the remainder was in coastal spring tillage, breeding birds being virtually absent from the hinterland. Large numbers of Lapwings and Golden Plovers were recorded in the first winter of study but many fewer in subsequent winters. Larger fields were used preferentially by both species and boundary quality appeared unimportant. Birds fed opportunistically on bare ground left from early harvested crops in late summer. Lapwings were found mostly on plough and stubble in early autumn, on cereals through the winter, with grass becoming important in late winter. Cereals held most Golden Plovers, and they showed a greater preference for cereals than did Lapwings. There was a large overlap in habitat use between the two species. There was no clear seasonal pattern in feeding. Lapwings avoided cereal fields where the blade height was greater than 110 mm, whereas the critical height for Golden Plovers was 9 mm. The rapid growth of autumn-sown cereals in 1994 and 1995 was considered to be the reason for the reduced population of both species using the region. It is considered that, if warm dry autumns become the norm, allowing rapid growth of winter cereals, the implications for the long-term conservation of Lapwings and Golden Plovers in southern England could be severe.

Shrimps and eutrophication in the waterbodies of a coastal grazing marsh

The influence of shrimps on turbidity was examined in laboratory and field experiments. Palaemonetes varians in the laboratory stimulated populations of both rotifers and Anabaena, which was the main cause of increased turbidity. In field experiments, P. varians increased and Neomysis integer decreased turbidity. In feeding trials P. varians took cladocerans and culicids in preference to copepods. It is considered that shrimps are likely to be important predators of cladocerans in shallow, coastal waterbodies and result in phytoplankton blooms, with reduced water transparency.

Ecology of eutrophic waterbodies in a coastal grazing marsh

The ecology of a mainly interconnected, complex system of smallwater-bodies on a coastal grazing marsh in the Greater Thames estuary,north-east of London, England, is described. Sixteen sites were sampled on aregular basis over a two-year period while 37 sites were sampled once in Mayto develop a site classification. Most sites were brackish and alkaline but,following re-wetting after drying out, the pH in some water-bodies decreasedsharply (minimum pH 2.7). All sites had high concentrations of phosphorusbut there were large differences; some, with good growths of submergedaquatic macrophytes, having lower phosphorus than other sites, which weredevoid of macrophytes. Internal loading with phosphorus was important.Nitrate levels were low.

Managing coastal grazing marshes for breeding waders and over wintering geese: Is there a conflict?

The winter grazing intensities of brent geese Branta bernicla, pink-footed geese Anser brachyrhynchus, and white-fronted geese A. albifrons, and the breeding densities of lapwing Vanellus vanellus, redshank Tringa totanus and snipe Gallinago gallinago, were related to the environmental characteristics of 81 fields within an area of coastal grazing marshes on the north Norfolk coast. Those fields grazed most intensively by geese in the winter supported lower densities of breeding waders in the summer than fields that were rarely grazed by geese. Lapwing, redshank and snipe all tended to occur in higher breeding densities on the wettest fields (characterised by large areas of surface water and Juncus spp., high soil moisture content and high water levels in field drains and adjacent ditches) and where vegetation was short (6–14 cm) in late March. The highest grazing intensities of geese were recorded on fields close to the roost sites with brent and grey geese rarely using fields at distances of greater than 5 km and 8 km from their respective roosts. The two species of grey geese tended to use those fields that were drier and located at greater distances from sources of disturbance with slightly longer (though still relatively short) swards than those used by brent geese. In a subset of the fields close to the roost site, brent geese used fields more intensively if they had been heavily grazed by livestock, had a short sward in October and if the soil was relatively impenetrable. The results suggest that waders, brent geese and, to a lesser extent, grey geese select areas of grassland with short vegetation, but that the former favour areas where the water table is higher than in those areas favoured by geese. It is suggested that this potential conflict may be relatively easily resolved either by temporal differences in management regimes, whereby water levels are raised in spring and summer and lowered in winter, or spatial differences in which some fields are managed for geese, preferably those close to the roost, and others for waders.

Mitigation of low stream pH and its effects on salmonids: G. L. Lacroix, Environmental Pollution, 78(1–5), 1992, pp 157–164

The winter grazing intensities of brent geese Branta bernicla, pink-footed geese Anser brachyrhynchus, and white-fronted geese A. albifrons, and the breeding densities of lapwing Vanellus vanellus, redshank Tringa totanus and snipe Gallinago gallinago, were related to the environmental characteristics of 81 fields within an area of coastal grazing marshes on the north Norfolk coast. Those fields grazed most intensively by geese in the winter supported lower densities of breeding waders in the summer than fields that were rarely grazed by geese. Lapwing, redshank and snipe all tended to occur in higher breeding densities on the wettest fields (characterised by large areas of surface water and Juncus spp., high soil moisture content and high water levels in field drains and adjacent ditches) and where vegetation was short (6–14 cm) in late March. The highest grazing intensities of geese were recorded on fields close to the roost sites with brent and grey geese rarely using fields at distances of greater than 5 km and 8 km from their respective roosts. The two species of grey geese tended to use those fields that were drier and located at greater distances from sources of disturbance with slightly longer (though still relatively short) swards than those used by brent geese. In a subset of the fields close to the roost site, brent geese used fields more intensively if they had been heavily grazed by livestock, had a short sward in October and if the soil was relatively impenetrable. The results suggest that waders, brent geese and, to a lesser extent, grey geese select areas of grassland with short vegetation, but that the former favour areas where the water table is higher than in those areas favoured by geese. It is suggested that this potential conflict may be relatively easily resolved either by temporal differences in management regimes, whereby water levels are raised in spring and summer and lowered in winter, or spatial differences in which some fields are managed for geese, preferably those close to the roost, and others for waders.

The loss of coastal grazing marshes in south and east England, with special reference to east Essex, England

Freshwater, coastal grazing marshes provide an attractive habitat for breeding and wintering birds. In recent years, such areas have frequently been subjected to drainage improvements and conversion to arable. In east Essex, a land-use study of 16 000 ha of the coastal zone between Clacton-on-Sea in the north to Burnham-on-Crouch in the south showed that between 1938 and 1981, the area of coastal grassland decreased from 11749 ha to 2083 ha—a reduction of 9666 ha (82%). Most of this loss (92%) has occurred as a result of conversion to arable. The rates of conversion to arable were particularly high between 1938 and 1947 due to wartime increases in agricultural production and from 1970–1981, coinciding with Britain's entry into the European Community and favourable cereal prices under the Common Agricultural Policy. The rate of loss of east Essex coastal grazing marsh is compared with that for three other areas: Romney Marshes, Kent; North Kent Marshes; and the Broadland Marshes of Norfolk and Suffolk.