Published in 2010 and sadly no longer in print, Jennifer Owen’s Wildlife of a garden - a thirty-year study has become a landmark for wildlife gardeners and indeed anybody who takes nature seriously. The author, an ecologist returning to Britain in 1972 from an academic life abroad and taking up a position in Leicester University’s Department of Zoology, settled in a suburban family home in Leicester and proceeded to log everything she found there over a period of 30 years. In what might be considered an otherwise unprepossessing suburban garden of 741 square meters, Dr. Owen logged an astonishing 2,673 species - of anything from plants to mammals, hoverflies being her self-declared specialist subject area.
She chose the words for the book’s epigram from a letter that Gilbert White wrote in 1786:
It is, I find, in zoology as it is in botany: all nature is so full, that that district produces the greatest variety which is the most examined.
Writing in the book’s forward, Chris Packham correctly noted that “this catalogue of skilful toil has few rivals anywhere”. “It’s a giant of a book”, he wrote, “the best of British, the handiwork of an endangered species - a naturalist who has found untold riches on her doorstep and has cultured the ability to identify, record and represent it in an eminently readable way”.
Although Owen mentions the trend for ‘wildlife gardening’ dating from the 1980s, she is at pains to note that her garden was not a wilderness but “a neat, productive suburban garden”. Photographs throughout the book show just that. There was a tidy, mown lawn at the back and herbaceous borders throughout. The gardening style seems much more English 1980s than what we might see today. Yet, overlain onto this were a set of deliberate policies: no chemicals (except the occasional slug pellet); planting of flowers for insects and fruits for birds; prolonged flowering with studious dead-heading; the development of a ‘structural heterogeneity’ with plants of different heights and growth forms; pruning and clearing delayed until winter; and maintenance of good ground cover by plants and weeds.
Against this backdrop, the resulting longitudinal audit produced quite staggering results:
| Flowering plants (including grasses) | 436 |
| Flowerless plants (including fungi) | 38 |
| Flatworms | 3 |
| Snails and slugs | 17 |
| Earthworms | 5 |
| Leeches | 1 |
| Woodlice | 8 |
| Centipedes | 7 |
| Millipedes | 5 |
| False-scorpions | 1 |
| Harvestmen | 11 |
| Spiders | 80 |
| Dragonflies | 7 |
| Grasshoppers and crickets | 4 |
| Earwigs | 1 |
| Psocids (‘booklice’) | 18 |
| Bugs | 183 |
| Lacewings and allies | 23 |
| Butterflies | 23 |
| Macro-moths | 282 |
| Micro-moths | 93 |
| Caddisflies | 5 |
| Hoverflies | 94 |
| Other flies | 51 |
| Sawflies | 91 |
| Ichneumons (wasps) | 533 |
| Other parasitic wasps | 24 |
| Ants | 2 |
| Wasps | 62 |
| Bees | 59 |
| Beetles | 442+ |
| Amphibians | 3 |
| Birds | 54 |
| Mammals | 7 |
| Total | 2,673+ |
[The remarkable numbers of ichneumon wasps recorded no doubt reflects the author’s research background - her PhD was on wasps. (There are in the region of 9,000 wasp species in Britain, although seeing 619 of them in any one place is simply staggering.) The author also acknowledges the species identification help provided by over 30 specialists, two of whom dealt with sawflies. (Who knew that there might be more than 90 of these?)]
This handsome volume is punctuated with tables - of species found in each of the categories above, of annual and seasonal variation within these groupings, and onwards down to very specific and fascinating detail so that the exact number of each species recorded over the 30-year period is set out.
One section helpfully explains methodology. For insects, various trappings methods were used. Butterflies were hand-netted, a process the author described as unsystematic but yielding an estimate of changes. A Malaise trap, kept continuously in place from 1st April to 31st October for 29 years, night and day in all weathers, intercepted flying insects. A second Malaise trap was used during 1978 on a small overgrown lawn in a different part of the garden, and this yielded a different and smaller insect collection, thereby justifying the effectiveness of the first trap. Pitfall traps were deployed from 1st April to 31st October between 1979 and 1990. These were small drinking beakers set into the ground, perfect for catching beetles, spider and ground-dwelling invertebrates. Half-filled with a weak formalin solution, these were emptied every two weeks. A mercury-vapour light trap was used for nearly 20 years to sample moths, most being released after identification. Finally, baited traps (using fermented fruit and either freestanding or suspended in trees) were used to attract, butterflies and hoverflies.
There are chapters on: Leicestershire; studying the Leicester garden; butterflies; moths; hoverflies; bees and wasps; sawflies, psocids, bugs, lacewings and their allies; beetles; other insects (mayflies, dragonflies, damselflies, grasshoppers and crickets, earwigs, ichneumon wasps and ants); other invertebrates; vertebrates; the habitat; gardens and conservation; changes and trends in garden fauna. Throughout, the botany of the garden, without which little of the above would be present, takes centre stage.
The value of this long-term study is self-evident. The author highlights the rising and falling numbers and the trend lines within these. For butterflies, their numbers increased in hot, dry summers that followed mild winters. Holly Blues and Speckled Woods, making their first show in the mid-1990s, become common thereafter. Macro-moths, hoverflies, bees and wasps in general register a clear decrease in numbers and species variety, hoverflies in particular being indicators of habitat variety. Solitary wasps showed a clear increase in the 1987–2001 period when summers were generally warmer and sunnier, with wetter autumns in this period having no effect as this is after the solitary wasp activity season. Ladybird numbers and variety were exceptional in 1975–7.
Outside these trends, the author draws some general observations of huge importance to anyone interested in promoting biodiversity. She recorded 264 different species of flowering plant (excluding grasses), of which 197 were intentional. This produced a varied and bountiful habitat of high plant and structural diversity. What she called “structural heterogeneity” was essential. A system of ecotones (transition zones between habitats) was also key. She wrote, “The creation of a state of permanent succession is thus a source of further enrichment of the fauna”. A garden that encompasses a multitude of potential ecological niches is one that will favour biodiversity.
There are few long-term studies of this nature from which we can gain insight. One can think of Gilbert White, whom the author quotes in the book’s epigram. One could add to that the 31-year study of a 2.1 acre forest food garden by Martin Crawford at Devon’s Agroforestry Research Trust, a long-term study of climate change mitigation in the context of food supply — one that, sadly, seems, at the time of writing, to be at risk of a shameful cancellation of its lease by the Dartington Hall Trust. The diligent accumulation of data over the long term has the potential to inform debate, policy and practice as we all move into uncertain territory in the face of climate change.