Ponds, Lakes & Reservoirs

Durham Lowland Priority Habitats
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Ponds, Lakes and Reservoirs Action Plan

Priority Habitats: PondsLakes and Reservoirs

Priorities
1.
Increase the number of water bodies valuable to wildlife through restoration or habitat creation, maintaining the diversity of habitat by varying size, depth and vegetation.
2. Identify and protect ponds, lakes and reservoirs of high biodiversity value from loss or degradation
3. Halt the net loss of ponds in the DBAP area.
4. Increase awareness of the biodiversity value of aquatic habitats and promote the principles of good pond management and creation.
5. Improve knowledge of ponds, lakes and reservoirs through survey, research and monitoring.
6. Maintain and enhance the ecological quality and diversity of existing water bodies and their associated fauna through appropriate management
7. Limit the spread of invasive species between waterbodies

Targets
Vision Statement: For there to be sufficient new pond creation to both replace ponds undergoing natural succession to fen and scrub, and to increase overall pond numbers.  For ponds to exist in complexes with wetlands of different ages and type. To protect all ponds through protection and management of surrounding land.

Target Type Unit Value
1. To increase the overall number of ponds in the Durham BAP area (whilst allowing losses only to natural succession). expand new ponds 160

Standing open waterbodies come in a range of types and sizes, some formed naturally and some man-made. Natural waterbodies occur in depressions created by glacial action, natural subsidence or river activity. Waterbodies formed by human activity include reservoirs, village green and garden ponds, ponds created by landowners for fishing, shooting, watering stock or amenity, ponds and lakes created by mining subsidence, water -logging of old brick pits, flooding of gravel pits, clay workings and bomb craters, and most recently by the clogging up or closure of pumps on agricultural land.

Waterbodies are classified according to their nutrient status: nutrient-rich (eutrophic waters predominate in the lowlands, where nutrient status is often artificially increased by agricultural fertilisers, whilst nutrient poor (oligotrophic) waters tend to occur in the uplands. Waterbodies with intermediate levels are classed as mesotrophic, and peaty and acidic Waterbodies, occasionally found in the uplands, are termed dystrophic.

Classification by size is arbitrary, but for the purposes of this plan, and for monitoring the priority habitat, a pond is defined as a temporary or permanent water body between 5 square meters and 2ha (5 – 20,000 m2) in surface area, which holds areas of open water for at least part of the year. The definition excludes garden ponds, which are covered in the gardens and allotments action plan.

 

Importance for Wildlife

All standing waterbodies have value for wildlife, particularly invertebrate and bird life. Around 3500 of the UK’s invertebrate species live in fresh water and up to half of these in ponds.  Over two thirds of Red Data Book invertebrates occur in ponds, as do 300 species of vascular plants, including half the UK’s wetland plants.

Larger waterbodies are of particular importance for bird life, especially those which include other related habitats such as fen (especially Phragmites australis reedbed), seasonally inundated grassland or wet woodland. These large waterbodies can often be improved for birds and other wildlife by providing more structural diversity, including undisturbed island areas for breeding.

Amphibians require waterbodies to complete the breeding cycle in spring and summer. Crucially they also need good foraging land and areas where they can hibernate and shelter nearby.

Small pools will quickly become choked with vegetation if left uncleared, and will naturally progress to basin mire and then scrub or wet woodland. This is often a valuable habitat in its own right, and supports a number of specialist invertebrates. However the retention of open water is often also a valuable conservation goal, and a balance has to be found between allowing natural succession and creating open water.

Ideally ponds exist in complexes of several waterbodies at different stages of succession, and in sufficient land to be able to create new ponds, as older ones dry up. This complex allows mobile open water species to avoid localised extinction, and allows the natural succession that favours others.

Where ponds are isolated, and where open water is seen as a crucial conservation factor, partial clearance may be necessary. However the development of linked complexes of pools across the landscape should be seen as a major conservation goal.

 

Distribution

In Durham there are approximately 1000ha of standing waterbodies, the majority of which are artificial waterbodies such as reservoirs. All the largest reservoirs are found in the west of Durham, mostly in the head of Pennine dales of Teesdale and Weardale, and smaller examples infringe on the upland plateaux further north, such as Waskerley and Smiddyshaw.

The open water-bodies alongside the River Wear at Witton-le-Wear have developed as a result of sand and gravel working. Brasside pond, near Durham City, is one of the largest areas of unpolluted water in Durham and developed following the abandonment of clay extraction. Naturally formed examples of waterbodies include the calcareous subsidence pools of Hell Kettles, the finest examples of limestone pools in Durham. Good examples of cut off meanders occur to the south of Durham City on the river Wear. Tarn Dub within Upper Teesdale is an important example of an upland permanent pool.

Ponds are thinly spread across the DBAP area, and are particularly rare in the North Pennines and Magnesian Limestone Natural areas.

Threats

  • Lack of data about pond locations and quality hinders conservation by making it difficult to identify priorities.
  • Isolation through the loss of surrounding semi-natural habitat.
  • Natural succession of ponds to dry land communities through build up of vegetation is not, by itself, a threat. However lack of replacement open water habitats nearby will lead to local species losses.
  • Over-zealous clearance of ponds to maintain open water communities often leads to losses of valuable fen and reedbed communities.
  • Point source and diffuse pollution (including abandoned mine discharges, run-off, atmospheric deposition and nutrient enrichment) are a serious threat to many waterbodies.
  •  Invasion or introduction of invasive plant species. Species such as Water Fern (Azolla filicoides) and Australian Stonecrop / New Zealand Pygmyweed (Crassula helmsii), can out-compete all other plants locally, leading to a loss of plant diversity.
  • Introduced species of animals can cause a range of problems. Mink are a factor in the decline of water voles; crayfish plague from American signal crayfish threatens native white-clawed crayfish.
  • Fish stocking of ponds can affect wildlife through competition, introduction of diseases and invasive plant species. Newts also suffer from predation of eggs and larvae by fish.
  • Loss of ponds to development.
  • Increases in recreational use can lead to pressure to control aquatic plants, increased littering and degradation of banks.
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