Floodplain Grasslands HAP

From Rio to Sussex

 

Action

Habitat

Download the Floodplain Grassland PDF file
Habitat
Current
Importance
Cultural
Trends
Potential
Current
Existing
Objectives
Targets
Costs
Actions
Monitoring
Consultation
Appendices
www.ukbap.org.uk

Floodplain Grasslands

Cuckmere -

1. Floodplain Grassland Definition

The habitat types covered by this plan are periodically inundated pastures or meadows with ditches which maintain water levels, containing standing brackish or fresh water. The ditches are especially rich in plants and invertebrates. Almost all areas are grazed and some are cut for hay or silage. Sites may contain seasonal water-filled hollows and permanent ponds with emergent swamp communities, but not extensive areas of tall fen species, although they may form a wetland mosaic with these types of habitats.

Naturally functioning floodplains are rare in the UK where most rivers are intensively engineered and regulated. The extent of the floodplain for flood defence purposes is defined as the area covered at the peak water level of a flood event of an appropriate return period. On rivers this will normally be the greater of the 1 in 100 year return period flood or the highest known water level.

Floodplain grassland can also be defined in terms of the National Vegetation Classification (NVC) scheme. This describes typical wet grassland communities as MG4 to MG13 (Rodwell, 1992). MG 4, 5, 8, 11 and 13 are agriculturally unimproved and of high plant species diversity, and therefore high conservation value; however MG11 is not found in Sussex. These unimproved habitats have been converted by drainage and fertiliser application to highly productive agricultural swards of MG 6 and 7. These are now the most common types of floodplain grassland. Although they have little or no floristic conservation value, they can be important for birds. MG 9 and 10 represent previously improved grassland subsequently abandoned or neglected.

 

2. Current Status and Distribution [top]

2.1 National

There is an estimated total of 300 000 ha of grazing marsh in the UK, and in 1994 an estimated 200 000 ha of this was in England (HMSO, 1995). However, only a small proportion (about 5000 ha in England) of this grassland is semi-natural with a high diversity of native plant species.

2.2 County

The Sussex Wildlife Trust estimates that there are about 11 400 ha of lowland wet grassland in Sussex (SWT, 1995). Areas of grazing marsh designated as Sites of Special Scientific Interest (SSSI) are all of national importance, and very good examples are found at Amberley Wildbrooks and Pevensey Levels. The rivers Arun, Adur, Ouse and Cuckmere all have important areas of floodplain grassland. The wet grassland resource in East Sussex is greater than in West Sussex according to an English Nature Report (Dargie, 1993), calculated at that time as 7720 ha and 4279 ha respectively. These calculations would suggest that there has been a 5% loss of wet grassland between the EN report in 1993 and the SWT report in 1995. Just under a half of Sussex floodplains consist of lowland wet grassland, however, much of this has been agriculturally improved and is now of little value for wildlife (SWT, 1995).

The following table lists the floodplain grassland SSSIs and SNCIs in Sussex. These areas have been concentrated on because they have already been assessed as having a high conservation value. It has been assumed that this is the area that needs to be conserved and maintained, and the other areas of floodplain have the potential to be restored to a high conservation value.

 

Floodplain Grasslands HAP

3. The Importance of Floodplain Grasslands [top]

Wet grasslands have a high nature conservation value and support a wide range of plant, bird and invertebrate species, many of which are rare and/or declining.

3.1 Plants

Approximately 500 species of vascular plants have been recorded from UK wet grassland and associated drainage channels (RSPB et al, 1997). The average height of the water table determines which species occur in an area. Drainage channels support some 130 of Britain s 170 species of brackish and fresh water vascular plants. Wet grasslands support several plants scarce in Sussex including narrow-leaved water-dropwort Oenanthe silaifolia (nationally very rare), cut grass Leersia oyzoides (Red Data Book - endangered), soft hornwort Ceratophyllum submersum (nationally rare), and sharp-leaved pondweed Potamogeton acutifolius (RDB - vulnerable).

3.2 Birds

Birds of Conservation Concern (1996) lists 37 red or amber list species which are at least partially dependent upon lowland wet grassland, of which 10 are totally dependent. The grasses, sedges and other plants tolerant of high water tables and winter flooding provide ideal feeding for grazing birds, such as wigeon and Bewick s swans (both amber list species). Large concentrations of wintering waterfowl may attract predatory birds such as peregrines, merlins and hen harriers. Seed crops produced by sedges and rushes are eaten by dabbling ducks.

Several species of wader regularly breed on lowland floodplain grasslands, including lapwing, snipe, redshank, and black-tailed godwit. Lapwing and snipe are amber list species which have been declining in number. The black-tailed godwit is a red list species because there are only 40 breeding pairs left in the UK (Appleby, 1994), threats include a decline in suitable habitat and the effects of flooding on nesting sites. There have been no recent records of breeding Black Tailed Godwits in Sussex although birds have shown territorial behaviour on occasions. The redshank is an amber list species, which is now sparsely distributed inland on wet grasslands due to land drainage and flood alleviation works (Batten et al, 1990). Waders exploit the larger invertebrates that are forced close to the surface by the high water table and shallow surface floods.

3.3 Invertebrates

Wetland grassland supports very large numbers of invertebrate species. Over a thousand nationally notable species have been recorded on wet grasslands, about a quarter of which are listed in Red Data Books. Pevensey Levels, in East Sussex, is one of only two sites in Britain where our largest spider, the fen raft spider Dolomedes plantarius, is found. Two species of snail, the shining ram s horn Segmentina nitida and the little whirlpool ram s horn Anisus vorticulus, which are priority species in the UK Biodiversity Steering Group report (HMSO, 1995) are found at sites in Sussex. S. nitida was formerly widespread but is now known from fewer than ten sites in southern and eastern England due to destruction of habitat and pollution. This species favours ditches choked with vegetation, therefore there should not be over-frequent clearance of ditches where this species occurs. Even more rare and threatened is Anisus vorticulus, which has declined at Pevensey and Lewes Levels (Kileen and Willing 1997).

The ditches of floodplain grassland are also important to Lepidoptera and Odonata. About 18 species of macro-moth are confined to ditch areas (pers.com. C.Pratt). The scarce hairy dragonfly Brachytron pratense, and the variable damselfly Coenagrion pulchellum are found in Sussex. Sites in Sussex are also important for many rare and uncommon aquatic beetles, including the great silver water beetle Hydrophilus piceus and Laccophilus poecilus (= ponticus).

3.4 Fish

Drainage channels and open water associated with floodplain grasslands support a number of species, including pike, roach, bream, rudd, eel, and species of stickleback. The more diverse the habitat, in terms of structure, extent and depth, the more species are likely to be present. Eels especially, are important prey for animals such as the grey heron and otter. Smaller species, such as stickleback, are important for kingfishers and grass snakes. Ditches can be important as spawning areas for fish as these provide still water so eggs and fry do not get swept away.

3.5 Amphibians and Reptiles

Flowing water is unsuitable for amphibians to breed in so ponds in the floodplain are utilised. However, water fluctuation on the floodplain presents an unstable environment which is difficult, in many cases, for amphibians to survive in. The great crested newt Triturus cristatus requires isolated ponds, uncontaminated with fish, especially in clusters. The only reptile that is often found in wet grasslands is the grass snake Natrix natrix, which is largely aquatic. These snakes require heaps of rotting vegetation to lay their eggs. Grass snakes and amphibians would benefit from a matrix of other habitats, such as scrub and floodplain woodland, with the floodplain grassland. (Both these species are priority species in the UK Biodiversity Steering Group report).

3.6 Mammals

Most mammals found in floodplain grasslands are also associated with a range of other habitats. However, these mammals include some rare species such as the otter and water vole (which have been identified as Priority Species by the UK Biodiversity Steering Group). Otters use drainage channels close to suitable rivers, though their range is affected by the availability of places to shelter in the daytime. Water voles also use the channels; their UK population appears to be in steep decline, probably associated with the increase in mink population and habitat loss. Therefore it is important to conserve floodplain areas as additional habitat for these species. Floodplain grasslands are also important areas for bats. They are prey-rich feeding areas for pipistrelles and noctules, especially important when in a matrix with other habitats including woodland edge and open water.

 

4. Importance of Floodplain Grasslands to People/Local Community and their Cultural Significance [top]

Natural or semi-natural floodplains are more appealing landscapes with greater wildlife interest than highly engineered areas. People prefer to visit natural areas rather than drained floodplains with arable fields cultivated to the very edge of the riverbank. As well as for conservation value, the maintenance, restoration and creation of floodplain grassland is important to gain other benefits such as:

  • storage of flood water giving flood defence benefit downstream;
  • trapping of sediment on floodplain leads to flood defence, water quality and wider environmental benefits (e.g. natural enrichment of soil leading to reduced need for fertiliser);
  • improvement in water quality by decreasing area of land under intensive management;
  • water resource benefits, such as improved aquifer recharge and fewer associated problems with low river flows;
  • passage of floodwater over floodplain leads to energy dissipation and a reduced risk of bank erosion and undermining of adjacent properties;
  • nutrient reduction through de-nitrification processes in damp soils which decreases nutrient loading from diffuse sources.

 

Floodplain grasslands have traditionally been used as summer cattle grazing pastures in Sussex. These areas were good pasture because the winter and spring flooding brought alluvial deposits which added nutrients to the grassland. This type of extensive livestock grazing should be conserved, promoted, and marketed since it is an example of a traditional way of farming and because it is beneficial to the grassland habitat. In many cases cattle are vital to ditch biodiversity, helping to maintain both rich marginal and emergent and macrophyte vegetation and their associated specialist invertebrates. The Sussex is the traditional local breed of cattle that was grazed on floodplain areas. These cattle are particularly suited to an extensive agricultural regime and their continued use helps retain the local historical and cultural links with the more traditional systems of the past. Many of the farms in Sussex have been occupied by the same family for several generations, and therefore have considerable interest in terms of local history.

 

5. Benefits to Local Business [top]

Floodplain grasslands can produce direct economic benefits from farming, or indirect benefits from activities such as tourism and education. The management of floodplain land for agriculture and conservation interests need not be mutually exclusive. Experience on the RSPB s West Sedgemoor Reserve in Somerset showed that initially, re-wetting of areas reduced interest for graziers (Evans et al, 1995). However, this was solved by improving the efficiency of the farming infrastructure: access for vehicles was improved; ditches were regularly cleaned to provide wet fences and drinking water; and a livestock husbandry service was operated by the RSPB. This resulted in demand for grazing outstripping grassland supply.

Reserves created to protect areas of floodplain provide a range of opportunities for the local community. Site managers would have to be appointed and skills of local volunteers would be developed. Reserves are valuable as an educational tool, both for school groups and other interested parties. The greater conservation value of large floodplain grassland and wetland reserves provides an attraction for naturalists and birdwatchers. This has implications for the local economy in terms of tourists using local accommodation and other facilities during their stay. Reserves also generate employment opportunities on-site in shops and cafes, and shops provide the opportunity for the sale of local crafts and produce. Furthermore, the High Weald Meadows Initiative, running in the High Weald AONB, has demonstrated that seed collected from meadows can be sold on a commercially viable basis.

 

6. Trends and Threats [top]

Prior to major land use changes 2000 years ago, there were an estimated 2 million hectares of floodplain in England and Wales, however there is now only 14% of this area remaining (Newbold, 1998). An estimated 40% of wet grassland was lost between the 1930s and 1980s (RSPB et al, 1997). In this time, the populations of breeding lapwing, snipe and redshank have decreased by a half. In addition, four out of the 43 UK species of dragonfly have become extinct since 1953 (RSPB, 1993). In Sussex there have been dramatic losses of wetlands; between the 1960s and 1980s over 60% of the wetlands in Sussex were intensively drained (SWT, 1995). Much of this land has been converted to arable cropping. Dargie (1993) estimates that there is an annual loss rate of 0.5% in West Sussex and 1.5% in East Sussex.

A driving force behind many losses of wet grassland has been UK and EU agricultural production above other considerations, such as wildlife conservation. The Agriculture Act 1947 guaranteed farm prices and aimed to achieve self-sufficiency in temperate foodstuffs. The UK joined the EU in 1973, and support for production was further increased through the Common Agricultural Policy. Conversion of grazing land to arable was encouraged by the government and facilitated by improved drainage infrastructure and efficiency. This led to the decreased conservation interest of many wetland sites. However, the most recent declines in floodplain grassland have been associated with lowering water tables and more intensive management of grassland.

As drainage and flood defence arrangements have become more efficient, the drier land has been able to be farmed more intensively. Lack of winter flooding reduces the attractiveness of grasslands to birds such as ducks, geese and swans. It also means that spring and summer water tables are lowered and many waders can not probe into the drier grasslands to feed. Reduced flood risk has encouraged farmers to invest in agricultural improvements. The grass sward has been improved by reseeding, fertiliser and herbicide application, enabling several silage cuts instead of one late hay cut. Improved land is dominated by one or two species of grass which can take advantage of the increased nutrients in the soil, therefore biodiversity is lost. Tall grass early in the season also hinders the movement of wader chicks and impedes lapwing feeding. On grazing marshes, the lowered spring water tables encourage farmers to put stock out to graze earlier and in greater numbers which can result in trampled nests and chicks. Just three cattle per hectare during the snipe breeding season can result in up to 80% of nests being trampled before hatching (O Brien, 1998).

The National Wildfowl Counts, organised by the Wildfowl and Wetlands Trust, appear to show that wintering wildfowl populations across the UK have remained stable or increased. However, examination of specific sites shows that this is because birds have moved to gravel pits and reservoirs. On natural sites they have become concentrated into a small number of floodplains so are vulnerable to disturbance and future habitat loss.

Drainage and flood protection works have been carried out for many centuries to protect life, housing and transport routes; to protect existing agricultural crops, and to claim and drain land for housing, industry, ports and agriculture. Historic, or former, flood defence activities continue to have deleterious effects. The problem is that previous activities on floodplains were very single-focus in their objectives so the consequences were not considered. In many cases the benefits are now marginal and the impacts extensive, so it is no longer appropriate, or cost effective, to maintain them.

Floodplains have been greatly modified in order to provide flood protection for developments inappropriately situated on floodplains and to allow future developments. This has been done by channelising rivers and isolating them from their floodplains by embankments. Land drainage and flood defence have lead to an early fall in water table levels in spring and rapid evacuation of winter floods. Low water levels are maintained in drainage channels in winter to increase floodwater storage capacity but this is detrimental to the many species that rely on water in the channels. Building developments on floodplains lead to restrictions on future flooding regimes and increased flooding of the remaining washlands. Urban development in these areas causes pollution problems from surface runoff and waste disposal.

Demand for water has increased dramatically in recent years resulting in over-abstraction. This has lead to lowered flow rates and river water levels, lowered water levels in wetlands, and the exacerbation of drought-related problems. Furthermore, lowered river and ditch water levels leads to lowered water quality because pollutants are concentrated in the remaining water. The demand for water will continue and will be greatly exacerbated by the housing development pressures facing Sussex.

These combined pressures on floodplains have caused fragmentation of sites. Isolation of areas of floodplain grassland makes colonisation by plants and animals difficult so specialist species are vulnerable to extinction.

The ditches that are typical of many agricultural floodplain grasslands are susceptible to neglect when farming ceases. They tend to silt up to such an extent that the aquatic flora is lost. Therefore rotational clearing is needed, as practised at Pulborough Brooks RSPB Nature Reserve.

 

7. Potential for Floodplain Grassland in Sussex [top]

Wetland systems have potential for habitat re-creation. Significant improvements in grazing marsh systems can be achieved by raising ditch water levels, allowing some flooding and by moving to more environmentally responsible farming practices. It has been shown that when water is initially returned to an area, bird populations take advantage of this and return (RSPB, 1993). However, to sustain these birds, populations of flood tolerant invertebrates are needed as food. If the land has been dry for a long time, the flood tolerant invertebrates will have died out and will take time to return to the area. However, if pockets of wet land holding invertebrate populations remain, these invertebrates will be able to expand their range into the new wet areas, and bird populations will be sustained.

Potential for wet grassland exists on all the major river floodplains. The floodplain area covers a total of 21 452 ha, 12 200 ha of this is fluvial floodplain, 9252 ha is tidal. If the area of SSSIs and SNCIs is subtracted from this, about 14 700 ha of floodplain is available potentially for grassland.

Opportunities for expanding the area of wet grassland occur wherever flood defence works are being undertaken. Allowing floodplains to function more naturally represents an ecologically sustainable solution to the problem rather than repeatedly repairing and renewing structures. Such opportunities may arise in the lower river valleys where existing flood embankments come to the end of their design life and where their renewal is prohibitively expensive. This would involve the creation of coastal grazing marsh as well as floodplain grassland. Such solutions will, however, only be adopted in appropriate circumstances.

When assessing areas for grassland re-creation, land that is of current low conservation potential is looked at. For example, areas adjoining Langney and Willingdon Sewers, near Eastbourne, could be reinstated as wet grassland even though the land does not have any conservation designation at the moment. The grassland is next to a residential area but scrapes could be created in the fields to allow wetter areas for birds and invertebrates. There are also areas that could be restored and re-created along the Adur valley.

There are opportunities for enhancement and expansion of floodplain grassland in the Arun valley and around Pevensey levels. Whilst it is crucial to ensure that the grassland areas at Pevensey are managed appropriately, the Pevensey Levels SSSI also includes about 1500 acres of arable land and there is also an area of arable land that was excluded from the SSSI site when it was re-notified. These areas could be reverted to grazing marsh to expand the Pevensey levels site. However, there are several arguments against the addition of an arable reversion tier to the Wildlife Enhancement Scheme in operation on the Levels (Lindsey, 1998). Firstly, the financial cost of this would be high and English Nature has only limited resources for this scheme, also one of the owners of arable land on the site has stated emphatically that he would not consider reversion. Secondly, although application of fertiliser to the arable fields contributes to the eutrophication of the ditches draining them, the view has been expressed that the arable areas do add to the diversity of the area by attracting species not normally associated with grazing marshes. Thirdly, because the traditional grips in these fields have been removed by cultivation, their drainage is impeded and pools created by heavy winter rain actually persist longer than in grazed areas. These wet areas attract overwintering birds, including large numbers of lapwing. Nevertheless, attempts to increase the area of arable cultivation should continue to be resisted.

 

Floodplain Grasslands HAP

8. Current Action [top]

Areas of floodplain grassland that are of conservation importance continue to be designated as SSSIs or SNCIs which gives them protection against built developments. SSSIs receive statutory protection whereby landowners are obliged to notify English Nature of any potentially damaging operations.

DEFRA requires Water Level Management Plans (WLMP) to be produced for each water-based SSSI. A WLMP is an agreement over control of water levels between landowners, the Agency and EN. The plan defines areas that require attention, outlines procedures for maintenance and recording/monitoring of the area, and sets an interval for reviewing the plan. Sympathetic maintenance and reprofiling, and water quantity are addressed by WLMPs. Water quantity can simply mean water level management in ditch SSSIs, but for other wetlands it may mean attending to the hydrology of the site with interactions between ground water and surface water tables having to be taken into account.

WLMPs have been written for several areas in Sussex. The Pevensey Levels SSSI area has been divided up into eight areas which have drainage systems that can be managed separately. Sub-plans have been written for five of the eight areas, two of these have been circulated to landowners whose comments have been noted. Where plans suggest changes in management or the installation of a new structure the Environment Agency will discuss the proposals with the landowners concerned. After the first of the individual sub-plans was completed in 1996, the Wildlife Enhancement Scheme funded five major sluices, installed by the agreement holders, at sites identified in the WLMP to control water levels in that block. The remaining plans are either in preparation or being circulated to landowners. The development of WLMPs offers the opportunity to raise water levels and encourage bird life, which has declined on the levels since pumped drainage was installed in the 1960s. However, in order for farmers to take up the management initiatives in the plan, realistic, long-term incentives need to be in place.

Amberley Wildbrooks was another priority area for the completion of a WLMP. The first plan has been written and was published in 1996; a two inch trial rise in water level across the brooks is being continued. Draft plans have also been written for Combe Haven, Milton Gate Marsh, Offham Marshes, Waltham Brooks, Upper Arun, Lewes Brooks and Arun Banks.

Lewes Railway Land Local Nature Reserve is an area (10.1 ha) of floodplain meadow and disused railway. The land is owned partly by a local farmer, Lewes District Council and Lewes Railway Land Trust. The land is managed sympathetically and cattle graze the meadows. There are plans to raise the water levels in the ditches in the next year (by 1999), this would reduce the need for fencing by creating wet fences. There is an area of reedbed that has been created along the old railway line. Since the site became a local nature reserve in 1995, surveys have shown that the species richness of the area has increased (pers.com., A.Kennedy).

Scrase Valley Local Nature Reserve in Haywards Heath is 7.7 ha of wet meadows (2.6 ha) and woodland on a tributary of the Ouse. Wet grassland plants are successfully being encouraged to spread by hay cutting in late August, and the coppicing of willow stands. Species important at this site are meadow thistle Cirsium dissectum, marsh cinquefoil Potentilla palustris and marsh speedwell Veronica scutellata.

The Ouse and Arun Valley Project Officers work with farmers and landowners to encourage environmentally responsible farming and promote the Countryside Stewardship Scheme. The project officers help farmers draw up management plans for their land and draw up and submit applications to Countryside Stewardship on behalf of the landowners and farmers. (from April 1st, 1999 the Arun Project expanded to include the Western Rother valley.)

In the Ouse Valley there are several projects for floodplain grassland creation. For example, at a farm near Sheffield Park, the new owners propose to revert approximately 15 ha of arable land back to floodplain grassland (using local provenance seed stock) with some floodplain woodland.

The Sussex Downs Conservation Board is currently in negotiations for a major wetland enhancement scheme at West Dean Brooks in East Sussex (32.4 ha). A draft management plan for this has been written.

The RSPB reserve at Pulborough Brooks is a good example of how floodplain grassland can be restored. Water levels within the site are managed to allow shallow winter flooding and flash flooding in some areas (RSPB, 1997b). Ditches were cleared and reprofiled, and are now cleared on a 3-7 year rotation. Along with the hydrological management, traditional mowing and grazing regimes were reinstated. The success of this management is shown by the increasing numbers of birds wintering and breeding on the reserve. The management has also been beneficial to other types of wildlife, such as the sharp-leaved pondweed Potamogeton acutifolius, which is in the Red Data Book.

Sussex Wildlife Trust now owns 81.8 ha of Amberley Wildbrooks SSSI, which is managed as a reserve by the RSPB. The site is managed in a similar way to Pulborough Brooks with hydrological management allowing winter splash flooding, and traditional cattle grazing regimes. This is a new reserve created when SWT purchased a further 49.4 ha in 1995/96. There have already been increases in breeding wader numbers and there is the potential for increases in breeding and wintering wader and waterfowl numbers (RSPB, 1997a). SWT also own reserves at Waltham Brooks (42.9 ha) and Pevensey Marshes (138.8 ha).

When the Agency s Flood Defence department carried out floodbank repairs to the north-west of Amberley Wildbrooks SSSI, an opportunity to enhance the wildlife value of the area arose. Spoil from the creation of scrapes was used to build up the flood banks. This work was done in partnership between the Agency, English Nature, Sussex Wildlife Trust and RSPB. The RSPB warden came up with the idea of excavating a tidal inlet from the River Arun to encourage reed growth for nesting birds. Even though the work was only recently completed, the scrapes have already shown an increase in wildlife.

Creation of an area of floodplain grassland at Tide Mills, south-east of Newhaven, is proposed. The total area of this is about 80 ha, though this is proposed to be a mosaic of habitats, including reedbed (pers.com., A.Tait, East Sussex County Council).

One of the problems for ditch systems is the introduction of alien species, such as floating pennywort, Hydrocotyle ranunculoides, in Hurst Haven, Pevensey Levels. This plant is causing particular problems because it grows very quickly, choking the waterway. Consequently, the flood defence value of the channel is reduced, other plants in the channel are shaded out, fish kills occur due to lack of oxygen, and there is an increased risk of livestock drowning. Research is being carried out into the growth characteristics of this plant, and its control, at the Centre for Aquatic Plant Management in Berkshire. A herbicide, 2,4- DAmine, was sprayed in 1998 to attempt to kill the floating pennywort. However, whilst this treatment initially reduced the area of coverage it did not totally remove the plant and the plant soon grew back to completely cover the watercourse and cause problems of localised flooding.

 

9. Existing Incentive Schemes [top]

The government is required to protect wet grasslands of international importance by the Ramsar Convention (the Convention on Wetlands of International Importance especially as Waterfowl Habitat 1971), the EC Birds Directive (79/409/EEC) and the EC Habitats Directive (92/43/EEC). These designations confer considerable protection upon relevant sites but do not necessarily provide the means for ensuring that such sites are managed in a way which optimises their importance for biodiversity.

The South Downs Environmentally Sensitive Area (ESA) was established in 1987. The overall aim of the scheme is to maintain and, where possible enhance the traditional farmed landscape and associated wildlife and historic resources of the South Downs by encouraging beneficial farming practices.

All farmers within the ESA boundary are eligible to enter into 10 year management agreements with MAFF, with an optional break clause after 5 years. Annual payments vary depending on the management practices adopted. In addition, payments are available for the provision of new public access and for a range of capital works.

The ESA scheme is based on a tier system. All agreement holders have to adhere to basic environmental measures and have the option of undertaking more onerous measures under other tiers. The payments for each tier are based on a calculation of the income foregone in following specific prescriptions, many of which can help conserve and enhance the biodiversity of the habitats concerned. The tier structure and prescriptions are reviewed regularly in order to provide the most appropriate management, with supplements for the more demanding regimes sometimes required.

The only tier aimed specifically at floodplain grassland is Tier 2: management of permanent grassland in the river valleys (L60/ha/pa). However, farmers in the river valleys can also enter Tier 3B: reversion of arable to permanent grassland (L250/ha/pa). As part of an agreed Conservation Plan, 30% grants are available for the creation or reinstatement of dykes and ditches and 80% grants for the construction of water penning structures (bunds, sluices and other works).

The ESA covers 51 000 ha, of which approximately 11 000 ha has been entered into various management tiers. The area of floodplain grassland under agreement in the ESA (up to and including 1998 agreements) was approximately 430 ha.

Countryside Stewardship is a MAFF grant aid scheme which is available throughout Sussex (primarily outside the areas covered by the South Downs ESA). It offers payments to farmers and other land managers to conserve and enhance the landscape and its associated wildlife and cultural history, and to help people enjoy the countryside. The Scheme offers 10 year agreements with annual management payments and a wide range of accompanying capital grants. Countryside Stewardship is a discretionary scheme with a limited budget and individual applications compete for the funding available. In order to ensure that the available funds are spent to the greatest effect, Sussex has a target statement aimed at identifying specific areas or types of land where key environmental objectives can be best delivered.

The current target areas most relevant in a floodplain context are the river valleys of the Adur, Arun, Ouse, Western Rother and Cuckmere and the High Weald. In these areas the restoration and enhancement of floodplain grasslands and the reversion of arable fields back to grassland are included as key objectives. The basic payment rates for extensive grassland management are 85/ha/pa and for arable reversion 280/ha/pa. During the period 1991-1997 there were 19 agreements in Sussex which encompass floodplain grassland.

The Organic Aid Scheme is available throughout England to farmers who wish to convert to organic production in accordance with the rules of the UK Register of Organic Food Standards (UKROFS). Although this scheme is not targeted specifically at UK Biodiversity Action Plan priority species or habitats, there can be biodiversity gains from organic farming. The organic standards require farmers not only to farm in the virtual absence of pesticides but also to conserve habitats and manage them sympathetically.

The Habitat Scheme was set up by MAFF in England to meet the mandatory requirement for long-term (20 year) set-aside. The only option of the Scheme applicable to Sussex is the maintenance and development of valuable wildlife habitats created under the Former 5 Year Set-aside Scheme. This scheme is currently under review and is likely to be merged with Countryside Stewardship in the near future.

The Set-Aside Scheme requires farmers to set aside land on which they are claiming under the Arable Area Payments Scheme. Within this there are advisory management regimes for the restoration of damp lowland grassland.

The Wildlife Enhancement Scheme (WES) was set up in 1991 by English Nature, and applies to the Pevensey Levels SSSI in Sussex. WES provides a financial incentive for farmers in the SSSI site to carry out sympathetic management. The objectives of the scheme are to conserve and enhance the plant and animal communities of the ditches; to maintain the attractiveness of the Levels for birds; and to encourage the continuation or reinstatement of the traditional management of the Levels. In order to achieve this, WES encourages ditch cleaning and reprofiling in a sensitive manner; grazing at low stocking rates; mowing only from July onwards; and no use of fertilisers. This represents Tier 1 of the Scheme, for which there is a payment of 22 per acre. If it is possible to maintain higher water levels in the ditches and create areas of splash flooding then a payment of 35 per acre are made. This is the Tier 2 option. Fixed cost payments are also available for items such as sluices, scrapes, and ditch restoration. Uptake for the scheme has been good, and there is now not much land left on the Levels that is eligible for WES. The existing scheme has been successful in protecting ditch wildlife but wetland bird populations have continued to decline.

As can be seen from this report, there is a plethora of schemes available to farmers, and this can cause confusion. A coordinated and coherent system of schemes is needed.

 

10. Objectives [top]

  • Identify the full extent and quality of existing areas of floodplain grassland
  • Prevent further loss, fragmentation or deterioration by ensuring appropriate protection and management that maintains and enhances all floodplain grassland sites
  • Undertake a planned programme of floodplain grassland resource expansion through the restoration of neglected or damaged sites and the creation of new sites
  • Implement suitable hydrological management to enable floodplain grassland enhancement and expansion
  • Implement, promote and market traditional farming methods (such as beef production) in order to maintain and enhance floodplain grassland areas
  • Increase floodplain grassland area to support viable populations of important floodplain grassland species

 

11. Targets and Costs [top]

  • Ensure there is no further loss of grazing marsh, and that the existing priority areas of floodplain grassland are under appropriate management by the year 2005. This could be done for existing SSSIs by reference to Water Level Management Plans which should identify target areas for management by providing appropriate advice to SNCI owners.
  • Restore at least 5000 ha of lowland wet grassland to a favourable conservation status by 2050. Achieve restoration of at least 1500 ha by 2010.
  • The national costed Habitat Action Plan assigns costs of 87 per hectare per year for management and enhancement of floodplain grassland (HMSO, 1995). This figure assumes that the proportion of private land under management schemes will increase from 26% in 1995 to 58% by 2010. The figure will not necessarily be the net cost to the public sector as there could be savings in reduced agricultural support payments.
  • Re-create 2000 ha of grazing marsh from cultivated land, in the vicinity of existing high quality wetland, by 2050 (subject to review).
  • Again, this has been costed at 87 per hectare per year by the UK Biodiversity Steering Group.
  • Ensure that the remaining areas of floodplain grassland in the major river valleys are subject to management agreements under Countryside Stewardship, WES or ESA schemes, as appropriate, by 2005.
  • Costs involve the payments made per ha and for direct works, also employment of project officers to promote the schemes.

 

12. Action Plan

 

13. Monitoring and Review [top]

This Habitat Action Plan will be monitored by the Sussex Biodiversity Partnership on an annual basis. This will include the monitoring of the fulfilment of the actions carried out against the targets set. A full review and updating of the plan will be carried out at five-yearly intervals.

 

14. References [top]

Abraham, Frances 1998. Amberley Plant Survey.

Abraham, F., Allen, S.D., Hodge, P.J. and Willing, M.J., A survey of the Flora and Fauna and selected invertebrate groups of the ditches of the lower Arun Valley. 1997 Arun Valley Countryside Project, Arun District Council.

Appleby, M. 1994. Agriculture and Environment: Opportunities in the UK under the AgriEnvironment legislation. RSPB Conservation Review 8:10-18

Batten, L.A., Bibby, C.J., Clement, P., Elliott, G.D. & Porter, R.F. (eds.) 1990. Red Data Birds in Britain. T. & A.D. Poyser, London

Dargie, T.C. 1993. English Nature Report Number 49. The Distribution of Lowland Wet Grassland in England. English Nature, Peterborough.

English Nature Magazine, 1998. Number 38.

Evans, C., Street, L., Benstead, P., Cadbury, J., Hirons, G., Self, M., & Wallace, H. 1995. Water and sward management for nature conservation: a case study of the RSPB s West Sedgemoor Reserve. RSPB Conservation Review 9:60-72

Fry, R. & Lonsdale, D. 1991. Habitat Conservation for Insects - A Neglected Green Issue. Amateur Entomologists Society, Middlesex. p.15 1-171

HMSO. 1995. Biodiversity: The UK Steering Group Report. Vol.2: Action Plans. HMSO, London

Kileen, I.J. and Willing, M.J. 1997. Survey of ditches in East Anglia and South-East England for the freshwater snails Segmentina nitida and Anisus vorticulus. English Nature Research Reports No 229. Peterborough: EN

Lindsey, B.I., 1998. Wildlife Enhancement Scheme: Review of scheme 1992-98 and scheme proposals for 1998 onwards. English Nature

Newbold, C. 1998. The nature conservation importance of floodplains in England and Wales -with particular reference to their flora. In: UK Floodplains. Bailey, R.G., Jose, P.V., & Sherwood, B.R. Westbury Publishing, Otley. p171-185

Newbold, C., Honnor, J. & Buckley, K. 1989. Nature conservation and the management of drainage channels. Nature Conservancy Council, Peterborough. pp.108

Newbold, C. & Mountford, 0. 1997. English Nature Freshwater Series No. 5: Water level requirements of wetland plants and animals. EN, Peterborough. 36pp.

Oldham, R.S.. 1998. Floodplains as amphibian habitat. In: UK Floodplains. Bailey, R.G., Jose, P.V. & Sherwood, B.R. Westbury Publishing, Otley. p.291-300

O Brien, M. 1998. Distribution and conservation of breeding waders on floodplain grasslands in the British Isles. In: UK Floodplains. Bailey, R.G., Jose, P.V. & Sherwood, B.R.Westbury Publishing, Otley. p.301 -310

Rodwell, J.S. 1992. British Plant Communities. Vol.3. Grasslands and Montane Communities.

UK. Joint Nature Conservation Committee (JNCC). Cambridge University Press.

RSPB, 1993. Wet Grasslands - What Future? RSPB, Sandy

RSPB, 1 997a. Amberley Wildbrooks Nature Reserve Management Plan

RSPB, 1997b. RSPB Pulborough Brooks Reserve Summary of Management Plan 1992-

1997.

RSPB, EN & ITE. 1997. The Wet Grassland Guide: Managing floodplain and coastal

wet grasslands for wildlife. RSPB, Sandy.

Sussex Wildlife Trust, 1995. Vision for the Wildlife of Sussex. SWT, Henfield

Willing, M.J. and Kileen, I.J. The Freshwater snail Anisus vorticulus in ditches in Suffolk,

Norfolk and West Sussex. English Nature Research Reports No. 287: EN

 

15. Consultation [top]

In preparing this Plan the following groups were initially consulted:- Butterfly Conservation, Country Landowners Association, East and West Sussex County Councils, relevant individuals in all the local councils, English Nature, Environment Agency, Farming and Rural Conservation Agency, National Farmers Union, Farming and Wildlife Advisory Group, High Weald Unit, RSPB, Sussex Amphibian and Reptile Group, Sussex Downs Conservation Board, Sussex Wildlife Trust, and Wildfowl and Wetlands Trust and the Conchological Society of Great Britain and Ireland.

 

Floodplain Grasslands HAP

16. Appendices [top]

16.1 Appendix 1: Requirements of Floodplain Grassland Species

16.1.1 Plants

Vegetation management (mowing and grazing) is important for conserving grassland communities because it removes plant material containing nutrients; prevents succession to coarser grassland and eventually scrub; and favours less competitive species, allowing greater species diversity. Traditional management techniques, such as hay-making and aftermath grazing, can create diverse swards. Hay cuts should be taken late in the year to allow plants to flower and set seed. Grazing the aftermath helps to create regeneration niches and promotes diversity of both species composition and structure (RSPB et.al., 1997).

The main botanical interest of floodplain grasslands is often in the ditches. These should therefore be of high priority for management to conserve their interest. Variation in drainage channel depths and profiles provides a range of conditions for aquatic species. Drainage channel sediments contain the seeds, turions and plant fragments that produce the next generation of aquatic macrophytes (RSPB et.al., 1997). Removal of these sediments should therefore be carried out rotationally to ensure that plants can recolonise. Rotational clearing of sediments will also remove plant nutrients and prevent waters becoming hypereutrophic.

16.1.2 Waders

Grazing animals maintain a short sward and may improve food supply for waders, which eat invertebrates associated with sheep and cattle dung. The problem is that the risk of nests being trampled is high, even at low stocking rates. Just 3 cattle per hectare during the snipe breeding season can result in up to 80% of nests being trampled before hatching (O Brien, 1998). Therefore, grazing should be delayed until early June to minimise trampling rates and increase wader productivity Rotational grazing (rather than free-ranging the stock over the whole grazing area) gives a variety of sward heights, and increases the range of habitat types for wildlife. If the area is mown for hay, aftermath grazing reduces sward height-and produces tussocks.

The water table should be maintained at 20-30cm below the soil surface throughout the breeding season by releasing water into ditches and damming. This encourages earthworms for the birds to feed on. Shallow linear depressions (simulating silted-up ditches) can be excavated to provide feeding areas. Bunds can be used parallel to the river to retain areas of shallow surface water or restrict flooding. Prolonged and extensive flooding of fields in late spring and summer is to be avoided as it inhibits nesting waders, reduces earthworm populations and hinders management of vegetation by grazing.

Redshank - Adults feed at edges of pools and ditches taking invertebrates from the water surface. Some prey are taken by probing in soft mud. Redshank nests are most abundant in fields with pools. Tussocks produced by cattle grazing provide nest sites.

Lapwing - Lapwings locate their food by eye and peck it from the surface of the soil and vegetation, they also take a large amount of earthworms. Highest nesting densities occur where the grass sward is less than 15cm in mid-May.

Snipe - Snipe probe into mud and soft soil for earthworms and insect larvae. Peat soils provide the best feeding conditions. They will feed among taller vegetation than other waders. Tussocks produced by cattle grazing provide nest sites. Snipe have a low nesting success but can extend their breeding season if the soil stays soft so they can feed (O Brien, 1998). The softness of the soil is maintained by keeping the water table high.

Black-tailed Godwit - These probe into mud and soft soil for earthworms and insect larvae, and also wade in shallow pools for mud invertebrates. Prefers to nest in short vegetation, highest nesting densities occur where the grass sward is less than 15cm in mid-May.

16.1.3 Amphibians

Most species of amphibian are adapted to a range of water depths. In general newts prefer submerged aquatic plants to lay their eggs on, and can tolerate a depth of 1-1.5m. Frogs lay their eggs in shallow water between 15-70cm depth where water temperatures are higher. Toad spawn is laid in strings around vegetation at 30-40cm depth (Newbold & Mountford, 1997). In general common toads prefer permanent water whilst other species will tolerate seasonal water bodies.

For all species it is essential that there is a stable water level after egg laying and that this is maintained during the breeding season. Drawdown isolates spawn and tadpoles making them vulnerable to predation and desiccation. After the young have left in August, most amphibians will tolerate the drying out of their breeding pond once every five years or so as this removes competitive fish populations.

16.1.4 Invertebrates

Terrestrial invertebrates of floodplain grassland are influenced by the vegetation structure and composition. A tussocky sward is particularly important as it provides a humid, litter-rich habitat; a refuge from large predators; protection from extremes of temperature; and overwintering sites. Most invertebrates are dependant on vegetation structure and not associated with a single plant species. However, plant-eating species may require the specific food plant in its correct growth form. Specific needs are relatively well known for butterflies. For example, the nationally notable marsh fritillary requires devil s-bit scabious and light winter/early spring grazing (RSPB et.al., 1997).

As with plant species, the drainage channels of wet grassland generally support larger numbers of invertebrate species than the surrounding grassland. In general it is necessary to maintain traditional ditch management to benefit a range of invertebrates. Rotational ditch clearing means there is always some partially vegetated water, ideal for water beetles, dragonflies and various other insects. However, it is also necessary to have choked ditches for some other insects, including a number of rare fly species (Fry & Lonsdale, 1991). Ditches cut with sloping sides would be preferable.

Shallow water is generally much more valuable to invertebrates than deep water. This is because in shallow water light is more likely to penetrate to the bottom; shallow water is also warmer and oxygen concentrations are higher. Most invertebrates occur in the shallows at the ditch margin. However, survival of some overwintering larvae may be threatened where only shallow water, liable to freezing, is maintained. Most aquatic wildlife is dependant on a stable water level over any year (Newbold et.al., 1989). Quality of water is crucial to both wildlife and drainage. Poor quality results in algal blooms and duckweed.

Most dragonfly species have a tolerance to a range of water depths, but are most vulnerable to water level drawdown during egg development. Many species do have drought tolerant eggs, but stable water levels are usually desirable during egg development in the autumn and following spring (Newbold & Mountford, 1997).

16.1.5 Molluscs

Rare snails on the Pevensey Levels include the little whirlpool rams-horn snail Anisus vorticulus, the shining ram s-horn snail Segmentina nitida, large-mouthed valve snail Valvata macrostoma and the false orb pea mussel Pisidium pseudosphaerium. All these species live in lime-rich drainage ditches, preferring established water plants in clean water characteristic of lightly grazed areas. Poached and grazed ditch margins are also important. These snails are vulnerable to over-shaded ditches, choked with algae, which are common around arable fields. They are also sensitive to over-frequent ditch clearance and so, in order to maintain populations, it is best to only clear short lengths of ditch at a time. This allows these poor colonisers to re-populate the cleared stretches from adjoining, uncleared stretches. (References Kileen and Willing, 1997, Willing and Kileen, 1998).

16.2 Appendix 2: National Floodplain Grassland Action Plan Objectives and Proposed Targets

From: Biodiversity - The UK Steering Group Report (1995)

Maintain existing habitat extent (300 000 hectares) and quality

Rehabilitate 10 000 hectares of grazing marsh which is too dry, or is intensively managed, by 2000. This would comprise 5000 hectares already targeted in ESAs.

Begin creating 2500 hectares from arable land in targeted areas. Target areas to expand existing areas and join up fragmented sites.

16.3 Appendix 3: EN Low Weald and Pevensey Natural Area Profile

Objectives for coastal and floodplain grazing marsh:

Encourage suitable grazing regimes to maintain and enhance sward structure.

Encourage ditch cleaning and reprofiling as and when necessary to maintain optimum conditions for flora and fauna.

Maintain water levels in ditches to prevent drying out and to maximise water volume.

Encourage a reduction in the use of fertilisers and herbicides to eliminate pollution.

Where appropriate and possible, encourage winter and spring flooding to restore conditions suitable for overwintering and breeding birds.

Secure protection of remaining unimproved grassland as part of a working pastoral system.

Encourage the formation of buffer zones around prime areas and along water channels through arable areas.

16.4 Appendix 4: Water Level Management Plans

Broad water level requirements:

SSSI ditches in grazing marshes notified for aquatic flora and fauna,. relict bankside interest - Summer water level stable, about 30cm below bank height, if land floods annually draw down in March or earlier for survival of semi-aquatic invertebrates. Winter dewatering of ditches is not recommended.

SSSI lowland wet grassland notified for herb rich grassland invertebrate interest - Summer water table 30-45cm below field level, if land floods annually draw down in March or earlier for survival of plants and invertebrates.

SSSI lowland wet grassland notified for overwintering birds - Allow splash flooding, i.e. shallow pools of water with intervening drier areas.

- SSSI lowland wet grassland -notified for breeding birds - Draw down from splash flooding around April/May or natural drying out of wet grassland.

These are general prescriptions but there will always be exceptions and most prescriptions will need to be fine tuned to particular site needs.

16.5 Appendix 5: Case Study - Pulborough Brooks RSPB Reserve [top]

Pulborough Brooks lies within the River Arun floodplain in West Sussex. The site was historically managed as water meadows. However, drainage improvements, including the canalisation of the River Arun (carried out in the late 1 960s), and water abstraction for domestic use from the Greensand aquifer (since the mid-i 970s) has led to the drying out of the area and intensification of agricultural use. These changes in agricultural practice, particularly the increase in area cut for silage and fertiliser use resulted in the deterioration of wildlife in the whole Arun valley. In addition, the site fell into dereliction during the mid-to-late 1 980s when farming totally ceased. The site was bought by the RSPB in 1989 and is a classic example of what can be done to restore damaged wetlands. The primary management objective is to manage the site for wintering and breeding waders and wildfowl by reinstating suitable mowing and grazing regimes together with appropriate hydrological management.

The hydrological regime of the site is fairly complex. There is a gravitational supply from the River Stor, which runs along the northern boundary of the site, this is backed up by the tidal influence on the River Arun sluices and by water from springs and seepage lines. The water levels in the Brooks largely depend on levels in the Rivers Arun and Stor. There are large sluices with tidal flaps which are generally used to let water out into the Arun, but they can be used to let water in on summer high tides. Smaller sluices let water in and out of the Brooks from the Stor. Only one of the sluices on the Stor is capable of supplying water to the Brooks at all times. From October to April springwater supply and run-off can create substantial flooding. Within the site flexi-pipe and drop board sluices allow independent water control in three hydrological units. Control of ditch water levels and flows allows shallow winter flooding on about 75% of the area, flash flooding on 10-15% during spring and autumn, and drain-down between June and September maintaining small scattered pools and wet areas. Ephemeral pools tend to provide an initial flush of displaced terrestrial invertebrates, plus opportunistic colonisation by animals such as chironomids. This is an important food source for wader chicks.

The majority of the drainage channels required reprofiling to enhance their wildlife value. Ditches were reprofiled or cleaned in July to October when water levels are low and birds have finished breeding. The ditches are then cleared on a 3-7 year rotation. Plant and invertebrate surveys were undertaken before work started to assess the success of the project. Short channels were reprofiled on one side only to reduce-the impact. Most channels were also widened. Spoil banks from previous ditch clearing were spread so there was no longer a raised bank. This allows water to spill out, producing muddy margins for wader and emergent vegetation. At sharp intersections of drainage channels, the corners were removed to produce islands or small, deep pools. Along some channel edges, grazing is prevented to allow reeds to grow.

The success of the RSPB management was shown by the fact that within three years of acquisition, the reserve had become nationally important for 11 wintering bird species. Establishment of the reserve also halted the decline in breeding waders in the Arun valley. Although the site only covers 10% of the wet grassland habitat in the valley, it supports over half of its breeding wader population. Figures 1 and 2 show how breeding and wintering bird populations have improved. However, even though the average number of breeding pairs of snipe increased with RSPB management, numbers have declined after an initial peak. This is because the initial flooding of arable land would have flushed out terrestrial invertebrates benefiting snipe, but then it will take several years for a typical assemblage of wetland invertebrates to recolonise the area and provide a long-term food source.

Improvement in the wildlife value has meant the site was given SSSI status in July 1998. The management regime has also been beneficial to other types of wildlife. The sharp-leaved pondweed Potamogeton acutifolius, which is listed in the Red Data Book as vulnerable, has increased its range from 11 ditches in the site in 1990 to 33 ditches in 1996, this is the majority of the suitable ditch area.

Projects for the future include a plan to create c.20 ha of reed-swamp on an area of low value grassland. This will be achieved by moving the embankment of the River Stor back and allowing the river to move within this new floodplain (pers.com. T.Callaway). The outfall from Wickford Sewage Works will then be re-directed into the reed-swamp to provide tertiary treatment for this effluent. This will provide a mosaic of habitats within the reserve. The reserve is a good example of how an area of floodplain grassland can be restored for its wildlife value. Despite the small size of the reserve, it forms a very valuable part of the River Arun floodplain along with Amberley Wildbrooks and Waltham Brooks.

References:

RSPB Pulborough Brooks Reserve Management Plan 1992 - 1997.

Callaway, T. 1998. Restoration of lowland wet grassland at Pulborough Brooks RSPB

Nature Reserve. In: UK Floodplains, Bailey (ed.) p.459-465

Callaway, T 1998. Pulborough. Interview, 6th August 1998

[top]

Floodplain Grasslands HAP