required) by extracting gravel which could then be sold to meet the demand from the
construction industry. These 'back door' gravel pits do not all have the advantages of the
more familiar flooded mineral workings. They usually lack the invertebrate-rich
surrounding terrestrial environment which is characteristic of the latter, and their use as
reservoirs means that they are liable to wide short-term fluctuations in water-level.
Nevertheless, the best of these sites compare very favourably with other still-water sites,
and may support as many as eight to ten breeding species.
Finally, the growing practice of creating garden ponds for their aesthetic and
environmental value has gone a considerable way towards compensating for the loss of
so many farm ponds. This is true just as much for some of common damselflies and
dragonflies as it is for frogs and newts. Even a very small and artificially-lined pond will
quickly attract two or three of the common damselfly species. Ischnura elegans and
Enallagma cyathigerum, in particular, as well as Aeshna cyanea, which is a noteworthy
coloniser of garden ponds. Very much the same comments apply also the creation of
ornamental ponds in parks and open spaces.
Ponds and lakes with this diversity of origins and uses have been recorded as the
breeding sites of seventeen species of dragonfly in Essex during the current survey
period. These include the nationally rare Lestes dryas and two very local dragonflies.
Cordulia aenea and Libellula quadrimaculata, both of which breed on certain of the
Epping Forest ponds.
(f) Coastal Ditches
Whilst the other still-water habitats in the county share many common
characteristics, and support a large range of species in common, the ditches associated
with the grazing marshes which lie within the sea-walls of much of coastal and
estuarine Essex have a quite distinctive dragonfly fauna. The grazing marshes
originated as reclaimed salt-marsh, and are criss-crossed with a network of drainage
ditches and wider 'fleets'. Excavation for the defensive sea walls also created extensive
borrow dykes on the landward side of the sea walls bordering the grazing marsh.
The sea walls themselves have developed their own distinctive flora and fauna, as
have the associated borrow dykes and drainage ditches. The dykes are cleared every
seven to ten years, which results in a range of habitats as re-colonisation by aquatic
plants and animals progressively takes place after clearing of each length of dyke.
Habitat diversity is also increased by differences in the depth and width of the dykes,
and by varying levels of salinity in the water. The characteristic plants of these dykes
include the Sea Club-rush. Common Reed. Reed-mace, and Fennel Pondweed.
At least twelve, and probably thirteen, species of Odonata have been recorded as
breeding species in coastal and estuarine ditches in Essex since 1980. Three of these.
Coenagrion puella, Aeshna cyanea and Pyrrhosoma nymphula appear to be rather atypical
of this habitat, however, and breeding records are rare (though they are. of course,
commonly found in other habitats in the county). A further three species. Ischnura
elegans. Enallagma cyathigerum and Sympetrum striolatum are ubiquitous species for
which coastal ditches are simply one expression of their adaptability to a wide range of
environments.
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