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Providing evidence to improve practice

Individual study: Some aspects of wildlife gardening increase numbers of flies, wasps and bees in urban domestic gardens in Sheffield, UK

Published source details

Smith R.M., Gaston K.J., Warren P.H. & Thompson K. (2006) Urban domestic gardens (VIII): environmental correlates of invertebrate abundance. Biodiversity and Conservation, 15, 2515-2545

Summary

Members of the public are encouraged to manage their gardens for wildlife by keeping ponds and compost heaps, providing nest boxes and food for wildlife and reducing chemical inputs. This study monitored invertebrates in urban domestic gardens in Sheffield, UK, and gathered information about the extent of deliberate wildlife gardening in those gardens.

Sixty-one gardens were surveyed for the following invertebrate groups between July and September 2000: Leaf-mining insects (tree foliage searches up to 2 m high); ground-dwelling invertebrates (3 pitfall traps/garden); litter dwelling invertebrates (extracted from 3 litter samples/garden by Tullgren funnel); flying insects (Malaise traps set for 2 weeks).

Information about the gardens was represented as 32 variables, including measures of habitat and structural diversity, plant diversity, the age of the house, the quantity of green space in the surrounding 1 ha and the presence or absence of compost heaps and ponds.
Three of these variables represented aspects of garden management, based on questionnaires issued to householders. One was an index of 'management intensity', calculated from scores for weeding, pruning, watering, dead-heading flowers, collecting autumn leaves, and fertilizer, herbicide and pesticide use. Slug pellet use was another variable. The third was an index of 'wildlife management', based on whether householders fed birds, provided bird nest boxes or used other (unspecified) methods to attract wildlife.

The abundance of hoverflies (Diptera, Syrphidae) was much higher in gardens with ponds (numbers not given). Long-legged flies (Diptera, Dolichopodidae) and social wasps (Hymenoptera, Vespidae) were also more abundant in gardens with ponds than those without.

The numbers of solitary bees (Hymenoptera, Apoidea), solitary wasps and hoverflies were related to the number of native plant species in the garden (this variable alone explained 56% of the variation in solitary bee numbers). There were more solitary bees in gardens with a lower index of wildlife gardening.

Solitary wasps (Hymenoptera, Sphecoidea, Vespoidea) were more abundant in gardens with composting than those without.

 

The numbers of snails and centipedes in litter samples were lower with higher management intensity, and the number of beetles other than ground beetles (non-Carabids) was higher with higher management intensity. The use of slug pellets (molluscicides) was associated with lower numbers of snails in pitfall traps.

 

Numbers of other invertebrate groups were related to other features of the gardens, but not to measures recommended for wildlife gardening.

 

Note: If using or referring to this published study, please read and quote the original paper, the abstract of which can be viewed at: http://www.springerlink.com/content/100125/