It's time to rake for progress

Even a tiny bit of garden can be transformed into a wildlife haven. Sanjida O'Connell learns how to dig for ecological victory

This week, thousands of us will enjoy the labours of the horticulturalists on display at the Chelsea Flower Show. And even though not everyone will be able to see the gardens at the Royal Hospital for themselves, many of us will look to the show for tips and gardening inspiration.

In a week crammed with discussions on all aspects of horticulture, much of our attention will be focused on the viability of eco-gardens. This year a number of environmentally friendly schemes are on show in Chelsea. Ellen Landscape Designs has built an eco-garden that features a natural swimming-pool filtered by plants. Giles Landscapes' "Wildlife Trusts Lush Garden" promotes biodiversity by leaving piles of decaying logs to attract bugs and frogs, and the Flying Gardener, Chris Beardshaw, has designed a recycled garden using recycled materials and plants grown in peat-free compost.

While fastidiously neat gardens were once the norm, today's gardener is likely to be more concerned with nurturing local wildlife than keeping his or her lawn neatly clipped. This heightened interest in green gardens is backed up by a new survey carried out by Sheffield University, aptly named the BUGS project (Biodiversity in Urban Gardens in Sheffield). It shows that, although there is still much room for improvement, our gardens are fast overtaking the countryside as the most important habitat for Britain's wildlife.

While many species have dwindled as a result of intensive agriculture, British gardens have seen an unprecedented rise in the diversity of species they support. While only 30 types of birds used to visit gardens, we now regularly see up to 80.

The BUGS project, led by Professor Kevin Gaston from Sheffield University's Department of Animal and Plant Sciences, was launched several years ago. Gaston realised that domestic gardens cover a significant proportion of our landscape, yet had largely been ignored by ecologists. "As urbanisation spreads, these areas become more significant in terms of biodiversity," he says. His initial survey of Sheffield found that a quarter (33 sq km) of the city centre was made up of gardens. In them, his team found 250,000 ponds, 45,500 nest boxes and 360,000 trees over three metres tall - more than are found in the equivalent area of countryside.

The BUGS team focused their research on 61 gardens that ranged from the tiniest back yards to plots of land ten times bigger. In these gardens the researchers found 4,000 invertebrates (including a rare moth that only breeds on juniper bushes), 80 kinds of lichen (including a species never previously recorded) and more than 1,000 types of plant. "Only a third of these plants were native to the UK, but this is hardly surprising seeing as most gardeners have access to more than 15,000 species at their local garden centres," says Gaston.

The BUGS team also discovered that, rather than comprising a single species of grass as many people think they do, our lawns now contain up to 159 different types of plant. The majority of species in the gardens they looked at were native, and some of the most common included rough meadow grass, rosebay, willowherb and Welsh poppy.

In fact, our lawns contain more plant species than any other grasslands in the country bar limestone meadows. The environmental broadcaster Chris Baines, author of How to make a Wildlife Garden, says: "I've been beating this drum for 30 years. I'm surprised that there's an astonishment at what these guys are coming up with, that gardens are not the degraded habitats they are thought to be. Why are we so interested in hay meadows, which are a totally manipulated habitat, yet have never turned our attention to suburbia?"

It is probably not a surprise that the biggest gardens contained the largest number of species, but Gaston insists that the tapestry of green spaces spread across our cities is more important in biodiversity terms. Our 15 million gardens make up the largest proportion of green space in our cities, and have a vital role to play in maintaining our environment. Baines says: "One of the most important things we have to learn is that nature is functional - it's the life support system that we depend upon. The interface between people and wildlife is also important - gardens are where a lot of people hear most of their birdsong and see butterflies."

Research shows that spending a few minutes a day in a green space can help combat stress, but it turns out that gardens are good for us in ways we might not have imagined. Heat tends to build up in the centre of cities and gardens have a cooling effect on our environment, as well as mitigating air pollution by filtering out poisonous chemicals and removing dust and asthma-causing particles from the air.

What Gaston finds particularly exciting, though, is that each and every one of us can make a difference, no matter how small our garden. He says: "There are 175,000 gardens in Sheffield, so if even ten per cent of owners could be persuaded to plant a tree, it would be done 17,500 times over." Certainly consumers have plenty of financial power, spending on average £2.62bn a year on garden products - which represents 1 per cent of household expenditure.

The BUGS team persuaded 20 garden owners to manipulate their gardens so as to test five central tenets of wildlife gardening. Not all their suggestions were popular: anyone who reads about how to attract wildlife will have been told to let small patches of nettles flourish for butterflies such as the red admiral and small tortoiseshell to lay their eggs on.

The 20 gardeners selected for the study were given large tubs of nettles and asked to create a patch about a metre in diameter. "People's tolerance was quite low," says Gaston wryly. But very few creatures colonised the patches. It turns out that it is important for butterflies to have much larger areas of nettles, certainly bigger than most of us would accept in a garden. Fortunately they grow profusely in derelict areas and on farmland.

Another myth that was laid to rest centred on bees' nests. Most lifestyle or garden catalogues offer expensive houses for bees, but few are ever colonised. What is successful, though, is to put out a simple home for mason bees or solitary wasps, such as a block of wood with holes in. These wasps are not the stinging type, but welcome guests that prey on caterpillars and other garden pests. Gaston also gave his gardeners miniature ponds 70cm long and 25cm deep, and even these tiny water bodies were able to support some wildlife.

I have two metal baths that are little bigger than this. In addition to diminutive water lilies, they hold water snails and water fleas, and birds frequently drink from them. Of course, the larger the pond, the greater the diversity of wildlife: in our other pond, which is nine metres long, we've seen more unusual species - not just frogs, but also newts, a lilac insect called a broad-bodied chaser and southern hawkers, an emerald and gold dragonfly. Pipistrelle bats also hunt over it in the summer.

Baines finds that many people dislike decay. The experimental gardeners were given piles of logs, which can provide shelter for creatures such as toads and hedgehogs, as well as a suitable surface for fungi and lichens to grow on. "One big difference between an ancient bluebell wood and my urban garden is decay," says Baines. "It looks like neglect and abandonment in a garden, but all wildlife is dependent on a cycle of decay."

Gaston's principle piece of advice is to plant small trees and shrubs as well as flowering plants, as they attract the greatest variety of wildlife. Baines advocates the creation of a woodland glade. His Victorian garden in Wolverhampton contains mature trees surrounding an open, sunny space. He says: "Species such as hedgehogs, blue tits, sparrowhawks and woodpeckers survive better in this type of garden than in what we perceive to be their real habitats."

www.sheffield.ac.uk/uni/projects/bugs; www.wildaboutgardens.org; "How to Make a Wildlife Garden" by Chris Baines, Frances Lincoln Ltd

Transform your little plot into a force for nature

Do

* Create a small pond

* Establish a variety of habitats

* Give your garden different levels by planting trees, shrubs and flowering plants

* Hang up bird boxes, bat boxes and homes for solitary wasps

* Put out sunflower and niger seeds and fat balls to encourage birds

* Leave piles of wood to decay

* In semi-shady areas grow woodland wildflowers, such as bluebells, wild daffodils, pink campion and foxglove

* Plant a tree that will grow to at least two metres

* Encourage climbing plants such as honeysuckle

* Establish a compost heap

Don't

* Use pesticides, particularly slug pellets or fertilisers

* Keep the garden too neat and tidy

* Use peat-based compost

Why the grass isn't always greener

There are an estimated 15 million gardens in the UK, most of which have a lawn. And while Kevin Gaston was delighted to find large number of plant species in our lawns, many of us still use harmful techniques in order to maintain them.

The country-garden ideal of a heavily manicured lawn tends to mean monoculture. Most consist of a single species, usually rye grass or creeping fescue, and support little biodiversity. While gardens generally are crucial to the survival of our native insects, birds and mammals, single-species lawns can be inhospitable places and contribute nothing to our flora and fauna.

Every lawn needs cutting, and alongside the plastics and metals used in their manufacture, lawn mowers guzzle petrol at an alarming rate. Electric mowers still use mains power, while push mowers are no longer commonly sold as they are perceived to be inefficient and time-consuming.

Keeping a lawn green via sprinklers and hose-pipes uses an estimated 1,000 litres of water every hour, more than the average family of four uses in a whole day, according to figures published by Southern Water.

Roslyn McKendry of the Pesticide Action Network says that garden chemicals comprise the fastest growing sector of the agrochemical market. A large proportion of these are used on lawns, including nitrogen-rich fertilisers, herbicides (used to kill moss and broad-leaf weeds), and pesticides (to kill insects). Even worms, one of the most beneficial of all our soil dwellers, have been targeted for leaving casts.

Although such chemicals have undergone increased regulation in recent years, only their active ingredients are tested. This means that toxic effects can still be produced when ingredients are combined to form a pesticide. This is known as "the cocktail effect".

Even so, many people feel that a such well-tended lawns are an essential part of the Great British garden, the sum total of which now comprise 270,000 hectares, far exceeding our combined area of national Nature Reserves. Around 90 per cent of British wild flowers and 70 per cent of British butterflies have disappeared in the last 20 years. If lawns were planted up or converted to wild-flower meadows, we could save on water, energy and chemical use and help save our native wildlife in the process.

Alice Klein