Ponds, Pools and Lochans

2. General information about ponds

2.1 Definitions

In this guide, ponds are defined as: Man-made or natural bodies of freshwater between 1m2 and 2 hectares in area, which hold water for all or part of the year.

This definition is deliberately broad. It includes lochans, peat pools and other naturally formed small waterbodies, as well as the full range of man-made ponds. It also includes seasonal pools - a distinctive type of pond which dries up in summer and which usually supports specialised, and sometimes valuable, pond communities.

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Figure 1. The geological record shows that ponds and pools were a natural feature of the landscape long before human activity began to shape the surface of the earth. This 1.5 ha natural lochan in Abernethy on Speyside was created during the last glaciation. Pond Action

Ponds are often perceived as essentially artificial habitats. This is not surprising since many ponds in the modern British landscape are, indeed, man-made. However, geological evidence and studies of pristine landscapes little altered by human activity, show that ponds and pools have always been a natural feature in landscapes worldwide. Long before human activity came to be the dominant force shaping the land, ponds were widespread and often abundant. In fact, it is clear that ponds are a very ancient and natural habitat type.

Scotland still retains many naturally formed ponds including lochans, dubh lochs (bog pools), dune slack pools and ponds formed from naturally cut-off river meanders. Many tiny natural pools also occur, particularly in areas with seasonally high water tables. For example, in undrained woodlands, tree-fall pools are often created in the depressions left when trees are uprooted in storms. Seasonal ponds can be especially common in the more natural landscapes where almost any depression on impermeable soils can hold water for part of the year.

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Figure 2. The creation of new ponds, like this one in the Auchenrodden Forest near Lockerbie, simulates the natural processes of pond formation. Pond Action

In the more intensively managed areas of the Scottish landscape, processes such as drainage and river channelisation have considerably reduced opportunities for natural pond formation. In these areas, man-made ponds, dug either deliberately (e.g. field ponds, moats) or created as a by-product of human activities (e.g. quarry pools), have largely replaced ponds created by natural processes.

However, whether called ponds, pools or lochans, and whether man-made or natural, small water bodies provide an essentially similar habitat type for pond wildlife. We know this because when the plant and animal communities from high quality man-made and natural ponds are classified using computer-based statistical techniques, the analyses show no discernible differences in their community types.

It is environmental factors such as water depth, geology, exposure to pollution and proximity to long-established wetlands which influence the biological communities in ponds, not the way in which the waterbody was made in the first place.

Ponds are, in fact, a very unusual type of freshwater habitat. The pond environment as a whole is both persistent and ancient. But many individual ponds, such as meander cut offs and tree-fall pools, are naturally short lived, often infilling within decades, to be replaced by new ponds which would, in pre-human landscapes, have been continually recreated by natural processes2. For these individually short-lived ponds, human activity, creating new ponds, has simply added a variety of new ways in which this ancient and natural habitat type is maintained in the modern landscape.

2 Exceptions to this include bogpools and seasonal ponds, both of which can be much more long-lived and persistent in the landscape.

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