Monday, 17 April 2000

Garden Bug Project

Urbanisation is occurring at a rapid rate throughout the world, and it is widely regarded as being detrimental to biodiversity. To maximise the potential benefit of urban environments on wildlife, it is essential to understand the roles of different urban land uses in the processes of extinction and colonisation, and hence their possible effects on biodiversity.  Domestic gardens have  the potential to play an important part in supporting urban biodiversity.  In the U.K., residential zones can account for more than 60% of urban land area. Consequently, private gardens  may represent a significant proportion of green space in  a city.  For example, they are estimated to form 27% of urban land area in Leicester.

Urban gardens will never act as substitutes for many semi-natural habitats, however, neither are they ‘wildlife deserts’.  Gardens can offer a rich variety of resources, such as a broad range of microclimates, plant species, and vegetation structures.  The potential diversity of wildlife is illustrated by the long-term study of one suburban Leicester garden, which was managed sympathetically towards wildlife, where more than 2200 animal and plant species were recorded!  Another study recorded more than 95 species of wild plant in a single garden.

Furthermore, gardens are not inhabited simply by common species.  The juniper pug is an example of a scarce moth whose natural foodplant is rare, but which successfully exploits ornamental junipers in domestic gardens.  Likewise, the stag beetle lives in tree stumps and logs in its larval stage, but these are a rather scarce resource in the wider environment. Their presence in gardens supports stag beetle populations in south east England.

Documenting biodiversity in domestic gardens
As these examples indicate, gardens may offer much potential as habitats for both common and rare or unusual species.  However, there are very few detailed studies of garden biodiversity, and those that do exist are restricted to individual gardens. Such research can not tell us how biodiversity varies between gardens.
Studies at larger scales usually concern groups of organisms which can be observed by garden owners.  Examples include the British Trust for Ornithology’s Garden Bird Scheme and the R.S.P.B. / Wildlife Trusts survey of thrushes and molluscs.  This type of study has proved very valuable but can not tell us whether the diversities of well-studied taxa are representative of other, less well known groups (most invertebrates, fungi, and even native plants), which would be expected to form the largest  component of garden wildlife.
Considering the extent of urbanisation, and the area of gardens within urban environments, there is a need to understand what features of domestic gardens, and of their surroundings, affect biodiversity.  However, until now these aspects have not been addressed systematically for a range of gardens.

How effective is ‘wildlife gardening’?
Although the study of garden biodiversity is limited, there is public awareness that gardens can be managed to encourage wildlife.  Much advice is available in books, magazines, and the media on ‘wildlife gardening’.  Some popular and widely advocated approaches include pond creation, growing plants as nectar sources for insects, installing artificial sites for nesting or hibernation by  birds, bats or insects, and neglecting corners of the garden.  Given the area of gardens in urban environments, if these activities are successful they may play a very important role in enhancing particular elements of biodiversity, and so contribute to urban conservation.
There is little doubt that ponds can attract species that were previously absent, or that bird boxes are used for nesting.  Nevertheless, the success of many garden manipulations in increasing the numbers and abundance of species remains unclear.  Which methods are most effective, and in what circumstances, and over what time scales do they work?  The efficacy of some of these creative conservation measures can be evaluated through detailed documentation and experimental trials.

The BUGS project
The BUGS project aims to improve understanding of the role of domestic gardens in urban biodiversity, using the City of Sheffield as a case study.  There are three main objectives:
1. To survey the biodiversity in a sample of representative domestic gardens from the residential areas of Sheffield.  The sample will encompass gardens along the urban- rural gradient, belonging to houses of a range of ages and styles.  We will record the numbers and species of numerous invertebrate groups (e.g. beetles, parasitic wasps, molluscs, spiders) collected by several sampling techniques, as well as birds, mammals, macrofungi and plants. Plants will be categorised according to whether they are native or introduced, and whether grown intentionally or not.
These measures of biodiversity will be related to garden characteristics e.g. size, aspect, vegetation structure, types of garden use, and chemical use.  Equally important will be the nature of the surrounding habitats, such as the proximity to other gardens, semi-natural habitats, waste ground or buildings.
2. To test the efficacy of some popular methods applied in wildlife gardening.  At present four experiments are proposed, a) potted nectar (buddleia) and food (nettles) plants will be introduced to gardens to test their abilities to attract and provide breeding sites for widespread butterfly species; b) artificial nesting sites will be provided to investigate whether they attract bumblebees and solitary bees and wasps; c) small ponds will be established to determine how they are colonised by aquatic flora and fauna, and what role  they have for non-aquatic species; and d) plots of lawn will be allowed to grow long to see if they can serve as breeding sites for grassland butterflies and other invertebrates.
3. To present a set of practical recommendations as to how gardens may best be managed to the benefit of biodiversity.  This information will be of use to garden owners and urban conservation initiatives, and hopefully longer term planning processes for urban areas.

Who is involved?
The project is being run from the Department of Animal and Plant Sciences, at the University of Sheffield, by Drs. Richard Smith, Kevin Gaston, Philip Warren, and Ken Thompson.  It is funded from 2000- 2002 under the Natural Environment Research Council’s URGENT programme of studies in the urban environment.
The success of a project such as this depends greatly upon the interest, enthusiasm, and participation of a variety of people and organisations.  We currently have local links with a battery of expert taxonomists and wildlife recorders, the Local Authority, and natural history and conservation groups such as The Sorby Natural History Society and Sheffield Wildlife Trust.  We have contact with national organisations too: English Nature, The Royal Horticultural Society, and Henry Doubleday Research Association.  All have a particular contribution to the project, and / or an interest in using and disseminating the results.

If you wish to take part in the project, what does it involve?
There are a number of different elements to the project.  We are interested to hear from anyone who would consider participating in any part of the program. Gardens of any type are suitable.  For the survey work we would like to arrange for access to the garden on a fairly regular basis throughout spring, summer and autumn.  We would like to make a description of the garden, record its flora and fauna, and ask you about how the garden is used (e.g. treatment with chemicals, use by children or pets).  We would sample the invertebrates by taking small amounts of leaf litter, and by burying some pots (to act as pitfall traps) in borders or vegetable patches.

In a selection of gardens:
We wish to erect a malaise trap.  This looks like a small tent made from fine netting, and it is used for sampling flying insects.  It would operate for short periods from spring until autumn.
We would like to conduct some trials of wildlife gardening techniques.  In the spring we would place out combinations of some pots of buddleia bushes and nettles, a small artificial pond (not dug into the ground!), and some artificial nesting sites for bumblebees and solitary bees and wasps (don’t worry, these insects either do not sting, or are quite docile; they are not the ‘yellow-jacket’ wasps that you see commonly in autumn, so your risk of being stung in the garden will not increase!).  Finally, if you are willing, we would like to arrange for a small area of lawn or rough grass to be left unmown for the summer.

There will be opportunities to participate in data collection for birds and other groups if you wish to do so.
Points of contact:

Dr Richard M. Smith,  Tel. 0114 2224822, (fax: 2220002),
e-mail: r.m.smith@sheffield.ac.uk
Dr Kevin J. Gaston,   Tel. 0114 2220030, (fax: 2220002),
 e-mail:  k.j.aston@sheffield.ac.uk

Biodiversity and Macroecology Research Group,
Department of Animal and Plant Sciences,
University of Sheffield,
Western Bank,
Sheffield, S10 2TN