Invertebrate survey at Gunpowder Park, the former Royal Ordnance Site in the Lee Valley
Proposed management for invertebrates
Invertebrate species may occur in a number of different habitats, they may have a range of differing
ecological requirements. Many species are likely to have complex life cycles, with different specific
requirements at different stages of their life cycle, but these requirements arc only known for rather
few species. This indicates the importance, especially to the rare and scarcer species, of a continuity
of habitat mosaic within an area.
The requirement of many invertebrate species for a suitable foraging area where nectar and pollen
may be gathered is paramount to their survival. Whilst many species may forage on a range of
flower species, others are highly plant-specific. In addition to forage areas, predatory species require
suitable hunting areas of open flower-rich vegetation, grassland or scrub that provide the specific
prey species and it seems probable that fairly extensive areas are needed by some species.
There is a parallel need for suitable larval development or nesting habitat and, in the case of parasitic
species, there is a requirement for the presence of the host Larval development may take place on
or in roots, stems, leaves, buds and seeds of plants or nesting may take place in the ground. For
stem nesting species it is critical that these resources remain in situ from one generation to the next
for the survival of these species and their parasites.
Open bare areas are an important and often undervalued resource. Bare soil offers a number of
benefits. In particular it warms up rapidly in sunshine, it is used by burrowing and ground nesting
species and for egg laying and it provides a clear visual field for predators (Key 2000).
Many species are associated with warm habitats, short dry grassland and disturbed ground. Sparsely
vegetated and bare ground areas arc valuable components of these habitats, and sandy substrates
are especially important to many aculeate Hymenoptera.
South facing slopes and banks arc important features providing conditions favoured by thermophilic
species at the edge of their range in Britain. The aspect and slope help promote summer drought
and the retention of open areas. Even quite small areas can be important to ground nesting species.
The diversity of flower-rich vegetation supports a variety of invertebrates that have feeding
relationships with the different plant species. The variety of flowers is an important forage source
for species of aculeate Hymenoptera and for invertebrates in general. The importance lies not only
with the range of flower species present but the continuity throughout the season. This is crucial to
bumblebees, which depend on a continuity of suitable forage sources throughout the spring and
summer for nest success, but also in providing specific pollen and nectar resources for different
species of aculeate during the year - many solitary bee species have short seasons where they are
dependent on specific forage species.
Many grassland invertebrates of conservation interest develop inside, feed on or over winter in
seeds and fruit heads and are therefore dependent on a continuity of these resources. The invertebrate
fauna is largely dependent on a low level of regular management combined with occasional
disturbance to enable the survival of species that develop inside leaves, stems, flower heads and
seeds and which over winter inside or at the bases of dead herbaceous stems and in ground litter.
For stem nesting species it is critical that these resources remaining in situ from one generation to
the next for the survival of these species and their cleptoparasites.
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Essex Naturalist (New Series) 21 (2004)