Managing Habitats for Dragonflies

Habitats: management problems and solutions

II. Ponds (water bodies of less than 1000 m2 and with Ph more than 6)

Ponds are particularly good for dragonflies because a large proportion of their water is shallow and they are often sheltered from wind though not from sun. By their nature, most are transient habitats and, unless managed, they quickly develop into marsh and, ultimately, woodland. Their management, therefore, is particularly important.

There is great scope for making ponds on both farms and in gardens. The guidelines for making small ponds on farms are the same as that for making them in gardens (see 'Dig a Pond for Dragonflies'). On farms it is easier to make larger ponds, but lining them with butyl etc. is usually prohibitively expensive; so larger ponds on farms have to be made in one of the following ways:

a) Dig the pond on an area underlain by impervious clay;
b) Dam a small stream. Permission must be sought from the National Rivers Authority (NRA). Ponds made by damming streams are liable to nutrient pollution if the stream flows through land treated with fertilizers. Such ponds are also liable to fill up with sediments brought down by the stream and will require frequent dredging. Only a part of the pond should be dredged in one year.

The management problems associated with ponds and their solutions are as follows:

  1. Shallow ponds rapidly become overgrown with water plants that have arrived naturally or have been introduced. Reeds and reed mace or bulrush are particularly liable to dominate ponds thus reducing the amount of open water and suitable habitat for submerged aquatic plants. Therefore, control these by cutting or pulling out when they first appear. If herbicides are used, restrict each application to a quarter of the pond to limit deoxygenation; the MAFF guidelines in Booklet 2078 must be strictly adhered to. It is obtainable free from MAFF, Lion House, Alnwick, Northumberland NE66 2PF.
  2. Trees and bushes at the pond edge cause the same problems as for lakes but in ponds can be more severe. In many ponds so many leaves fall into the pond that they poison the water. Therefore, do not plant willows etc. close to ponds or, if you do, control their growth frequently.
  3. Nutrients and pesticides can enter ponds by streams or drift. Nutrients cause algal blooms and excessive growth of duckweed. Therefore, as far as possible prevent spraying in the immediate vicinity of the pond and feeder streams. If the time of pollution is predictable, for example when the fields above the pond are sprayed, cut off the stream with a dam where it enters the pond, and allow polluted water to bypass the pond through a previously prepared ditch.
  4. Do not introduce non-native water plants, such as Crassula helmsii, which can take over a pond.
  5. Many farm ponds, small gravel and clay pits, etc. are used as dumps for rubbish, some of which can be very toxic. Therefore, if an old pond is being renovated, it is important to clear rubbish out of it before it is allowed to refill.
  6. Farm stock can muddy ponds to such an extent that submerged plants cannot grow in them and emergent vegetation is lost by trampling. Therefore, where this occurs, restrict access of stock to a part of the pond with fencing that extends into the pond. Similarly, in urban areas, anglers, children (and even dragonfly enthusiasts!) can severely damage bank side vegetation. In such places, exclude people from part of the pond by fencing.
  7. Ponds are even more susceptible to manuring by wildfowl than are lakes. A small pond can rarely take more than one pair of mallard. Therefore, do not use ponds for domestic geese, ducks or ornamental waterfowl if you want dragonflies on the pond.
  8. Adult dragonflies at ponds close to houses or farm buildings, where there are exceptionally large populations of house sparrows, can be severely affected by predation. Newly emerged dragonflies are especially vulnerable. Therefore, avoid siting new ponds in such places.
  9. Dragonfly larvae in ponds, as in lakes, are vulnerable to predation by fish if these are kept in unnaturally large numbers. Therefore, if possible avoid stocking ponds with goldfish, carp, etc. if you want the ponds to be suitable for dragonflies.
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