Temporary ponds and scrapes
Despite their tendency to change between wet and dry, temporary ponds support a vast array of wildlife.
Drying out prevents fish from establishing, providing a predator-free environment for tadpoles and many aquatic invertebrates to thrive.
Temporary pools and scrapes hold water for periods of the year, but dry out in most years. Prior to extensive land drainage, it is likely that temporary ponds were a much more common part of the landscape, particularly in semi-natural habitats such as grassland.
Temporary ponds are often overlooked within the farmed landscape, but are a highly threatened habitat type. They have declined significantly in the landscape due to drainage, but as well as some temporary ponds persisting in semi-natural habitats such as grassland and heathland, the feature can be extremely valuable in arable fields.
A huge variety of wildlife uses temporary ponds and they often support rare and scarce species which thrive in the unique combination of periodic flooding and drying. Many scarce plants and insects are associated with the damp muddy margins that are exposed as temporary ponds dry out.
The regular drying out of temporary ponds prevents fish from establishing. Free from predators, tadpoles and aquatic insects such as water beetles can often thrive. In fact many species of aquatic insect, and some amphibians such as great crested newts, are seldom found in ponds where fish are present.
When holding water, temporary ponds will support many kinds of wildlife in the same way that a permanent pond would. Many generalist aquatic insects will use the pond and beneficial insects such as bees will drink from ponds while many hoverflies, one of our key wild pollinators, need water to complete their lifecycle. Amphibians rely on ponds for breeding, and grass snakes are strongly associated with ponds as their diet consists of frogs, toads and newts. Birds and mammals in arable areas often rely on ponds for their drinking water.
The natterjack toad is a rare amphibian which may be found on farmland in Cumbria, north Wales and southwest Scotland. These toads require shallow, temporary ponds, which are predator free to breed. Terrestrially they need habitat consisting of very short vegetation and bare ground, with suitable ground in which to burrow.
Clean water is a vital part of a healthy pond – many of the species that rely on ponds cannot survive in very nutrient-rich or polluted water. The often small volume of temporary ponds makes them extremely vulnerable to pollution and also to changes in drainage.
Temporary ponds in existing semi-natural habitats such as grassland and heathland should always be protected from any land management practices. It is essential that temporary ponds are not deepened to hold water all year round. This removes many of the key features that support specialist wildlife.
Many temporary ponds are often overlooked or viewed as simply waterlogged areas or muddy hollows, particularly when dried out and grass dominated but it is important that these seasonal pools are not drained or filled.
Although many temporary ponds can have great longevity, some will naturally fill in over time as sediment is deposited with inflowing water. However, temporary ponds are often best left unmanaged, even when they begin to become silted up or over-vegetated. In this instance it may be better to prepare for the future by creating a new temporary pond nearby and to allow existing temporary ponds to naturally dry out. If a mix of existing and newly created temporary ponds is created, a range of different conditions will be created to suit a wider range of wildlife.
To create a new temporary pond or scrape, try excavating a shallow depression in nearby areas with a similar underlying soil type. This is best situated in a sunny, open area, free from tree cover. Ensure that the margins have a shallow gradient to maximise the bare muddy margins which are exposed as water levels recede and resist the temptation to dig a deeper pond which would hold water for much of the year. Where there is room, consider creating a network of different scrapes around the farm to different depths. There will be no need to plant up the scrape, which will be naturally colonised by both terrestrial and aquatic species as it settles.
Buffering temporary ponds in arable areas can help to reduce the impact of farm inputs and pollution. Ideally the buffer around an arable temporary pond should be at least 12m. The best place to site ponds is in permanent pasture, however a wide buffer strip planted up with a mixture of robust grasses will mimic this habitat, providing the grassy margins that benefit amphibians, especially newts and toads. The ponds should be linked to other key habitats by appropriate terrestrial habitat, such as buffer strips, rough grassland and hedgerows allowing animals to move between different water bodies, forage and migrate to hibernation areas as necessary.
Here are some useful case studies and articles about how farmers are putting Farm Wildlife into practice on their farms
Author: Gavin Thomas Farm: Chipping Moss, Leagram Estate, Forest of Bowland, Lancashire Aims: The primary aim was to restore upland in-bye wet grassland for breeding lapwings, redshanks, oystercatchers, snipe and curlews. By managing rush cover and water levels it was also hoped that the quality of pasture available to grazing livestock would also be greatly improved. […]Read More