Britain’s gardens have a greater diversity of wildlife than much of the countryside, which has been “trashed” by modern farming, according to an expert on urban ecology.

Even the smallest urban garden can contain a range of plants and insects that makes most farmland look like “biological desert”, said Dr Ken Thompson, a senior research Fellow at the University of Sheffield. “I know it’s a heretical thing to say but most farmland would be improved by having a housing estate built on it from a biodiversity point of view,” Dr Thompson said. “If you’re comparing gardens with the equivalent area of modern intensive farmland, gardens are much better.”

While fields tend to be devoted to a single crop, gardens are usually home to a greater variety of plant and invertebrate life, said Dr Thompson, who led the Biodiversity in Urban Gardens in Sheffield (BUGS) project.

It found more than 1,100 varieties of plants — more than two thirds of British native flora — and 700 species of insects and other invertebrates in the gardens studied.

Speaking at the British Science Festival yesterday, Dr Thompson said: “Most of Britain is farmland, it is intensively managed, drenched in fertiliser and desperately poor in wildlife. Typical improved farmland is a bit of a biological desert. Organic farmland is better, but not a lot better — still not as good as a garden.”

But Britain’s 16 million gardens cannot save the full range of the nation’s biodiversity alone because they struggle to replicate the ecology of areas such as marshes, heaths and coastland, Dr Thompson said.

“There are areas of unimproved woodland and heathland which still have a rich biodiversity,” he said.

In a 30-year study, Jennifer Owens, the ecologist, found more than 8,000 species in her own suburban garden in Leicester, 20 of them previously unknown in Britain.

Dr Thompson said that comparatively little effort was needed to turn a typical garden into a haven of biodiversity.

“The top thing, far more important that anything else, is you need more big shrubs, trees and hedges. You massively increase the volume of vegetation. It’s a lot of places to live and lot of stuff to eat.”

Putting less effort into the garden could make it more attractive to many species, he said. “Don’t be too tidy — don’t be in a hurry to clear up everything the moment it stops flowering or hoover up every fallen leaf.”

Digging a pond and starting a compost heap would also help a typical garden to attract a greater diversity of wildlife, but decking was a “disaster”, he said.

Although Dr Thompson said that most British bumblebees do better in the garden than in the countryside, he advised against buying any of the nest boxes for bumblebees and ladybirds. He said: “Most of them are a complete waste of time.”

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