Several species which are rare, or extremely local in Essex have gravel pits as their
favoured breeding sites. These include Coenagrion pulchellum which was present at a
gravel pit site in the south-east of the county in the mid-1970s, the very local Erythromma
najas and Libellula quadrimaculata (the Four-spotted Chaser). Cordulia aenea is another
extremely local species in Essex, and at least two of the ponds from which is has been
recorded had their origins in mineral extraction in the last century.
Unfortunately, the larger pits made with steep and regular sides by modern
machinery provide less habitat diversity than the older ones, and new techniques of
land-filling make possible reclamation for agriculture or other profitable use. We can
expect, therefore, that the supply of worked-out pits suitable as dragonfly habitat will
decline in the future unless specific priority is given to creation of wildlife habitat in
areas vacated by the extraction companies. Other threats to flooded pits as dragonfly
habitats include their conversion for incompatible recreational uses such as bike-
scrambling. Depending on the management regime adopted, the use of pits for angling
has variable consequences for the dragonfly fauna. Over-stocking with fish is a threat to
the nymphs of many species, whilst too much overhanging tree-cover inhibits the
development of the requisite aquatic and marginal vegetation. Most species require a
combination of both sheltered and open, well-illuminated water-margins. In the long
term, of course, drying-out and encroachment by scrub and secondary woodland will
eliminate the dragonfly populations of these sites, so that their continual replacement,
as well as active management, is required.
(e) Farm and Garden Ponds
Although farm ponds may have a range of uses such as angling, wildfowling and
irrigation, their main use historically has been as watering-places for cattle and other
stock animals. The replacement of ponds by piped water-supplies, as well as the
widespread shift into arable farming, has caused a dramatic decline in both the
numbers and quality of farm ponds. The Nature Conservancy Council (N.C.C., 1982)
estimates that over half the farm ponds in certain lowland counties of Britain have been
lost in the last half-century. Some of these have been filled in. whilst others have simply
dried out through neglect. Many more surviving ponds, now functionless. have been
allowed to become contaminated by rubbish-dumping, silage liquor or agricultural
chemicals such as fertilisers and insecticides Except where they are deliberately
maintained for their traditional use. or for recreational, environmental or aesthetic
reasons, farm ponds have largely ceased to be the important wildlife sites they once
were.
Where farm ponds are well-maintained, with shallow, gently sloping and well-
vegetated margins, they may support a rich diversity of breeding dragonfly species, as
well as "visiting" species which may hawk for invertebrate prey over ponds in which they
do not breed. Even quite small farm ponds may support live or six species of damselfly,
including such localised species as Pyrrhosoma nymphula (the Large Red Damselfly)
and Lestes sponsa. Several species of darter, such as Sympetrum striolatum and hawkers,
such as Aeshna cyanea, will also breed in farm ponds.
A particular feature of Essex (see Corke. 1984. p. 123) has been the common practice of
establishing farm reservoirs (for which planning permission was not. for sonic lime.
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