April 11 2006: Dr. Ken Thompson

April 11th, 2006

Dr. Ken Thompson
(Department of Animal and Plant Sciences, University of Sheffield)

The biodiversity of domestic gardens

Abstract

Combining analyses of digital imagery and randomised telephone surveys, we conducted the first detailed audit for a major urban area of the size and nature of the garden resource and its associated features. This revealed that c.23% of the area of urbanised Sheffield comprises domestic gardens, and that these contain estimated totals of 25,200 ponds, 45,500 nest boxes, 50,750 compost heaps, 360,000 trees (>2m in height), and a population of 52,000 domestic cats. 

The relationship between the features of gardens and biodiversity was studied in 61 gardens in the urbanised region of Sheffield, chosen to maximise variation in house type and age, garden size, and location within the urban area. A detailed sampling regime was employed to obtain comparable estimates of the species richness and abundance of a variety of taxonomic groups (including lichens, macro-fungi, liverworts, mosses, molluscs, spiders, beetles, sawflies, aculeate Hymenoptera, craneflies, hoverflies). Patterns of surrounding land use were also determined for each garden.
 
In some taxonomic groups with relatively few species, most were widely distributed, but in more speciose groups, about half were found only in a single garden. Most species detected are known to be common, but some are not, confirming the importance of gardens for the conservation of invertebrates (numerous new vice-county and extreme latitudinal species records were obtained, some species known to be generally rare were found quite commonly in gardens, and one species new to Britain and one likely new to science were found). Neither numbers nor diversity in different taxa were related to garden features in a consistent way,  and some widely-held beliefs about garden biodiversity, in particular that large gardens, suburban gardens and those with many native plants  should be superior to small gardens, those distant from the city edge, and those with fewer native plants, were consistently not supported in our data.  However, the three-dimensional complexity of gardens (particularly the presence of mature trees), and their topographic position are both important determinants of local biodiversity.
 
We introduced several simple manipulations to several gardens: artificial nest sites for solitary bees and wasps and for bumblebees, small ponds for breeding invertebrates, dead wood for fungi & saproxylic organisms, and patches of nettles Urtica dioica L. for butterfly larvae. The broad conclusion is that whilst some methods for increasing the biodiversity of garden environments may be very effective, others, though widely recommended, seem to have rather poor success rates on the timescales and spatial scales likely to be acceptable to garden owners.

Key publications

Thompson et al. 2003. Urban domestic gardens (I): Putting small-scale plant diversity in context. J. Veg. Science 14: 71-78. (pdf).
Thompson 2003

Smith et al. 2005. Urban domestic gardens (VI): environmental correlates of invertebrate species richness. Biodiv. Cons. online first (pdf).
Smith 2005

Smith et al. 2006. Urban domestic gardens (IX): Composition and richness of the vascular plant flora, and implications for native biodiversity. Biol. Cons. 129:312-322. (pdf)
Smith 2006

Curriculum vitae

I did my PhD with Phil Grime in Sheffield and, after a short spell at Durham University, spent the 1980s at Plymouth Polytechnic (now University). I returned to Sheffield in 1990, and have been there ever since.
 
I’m interested in (and have published on) most aspects of plant ecology, including the ecology of seeds, plant traits and functional types, biodiversity and ecosystem function, biological invasions, urban ecology, commonness and rarity, changing climate and land use. I am editor of Functional Ecology and Seed Science Research, and the author (with Jan Bakker and Renée Bekker) of ‘The Soil Seed Banks of North-West Europe: Methodology, Density and Longevity’ (1997, Cambridge University Press) and (with Mike Fenner) of ‘The Ecology of Seeds’ (2005, Cambridge University Press). I’ve also published over 100 papers in refereed journals.
 
I’m increasingly interested in the science of gardening. I was one of the leaders of the ‘Biodiversity in Urban Gardens in Sheffield (BUGS)’ project, and I have published two popular gardening books: ‘An Ear to the Ground; Garden Science for Ordinary Mortals’ (Eden Project Books, 2003) and ‘No Nettles Required; The Reassuring Truth about Wildlife Gardening’ (Eden Project Books, 2006). A Dutch publisher has recently enquired about the translation rights for the latter book! I’m working on another gardening book to be published early in 2007.