Victoria Summerley: Town Life

"They paved paradise and put up a parking lot." Good grief, did Joni Mitchell write "Big Yellow Taxi" nearly 40 years ago?

We haven't learnt much since then. As Britain's urban conglomerations spread their tentacles ever further, the latest piece of paradise to come under threat (or rather, under paving) is the front garden.

According to the London Assembly, 14 per cent of front gardens in the capital are now more than three-quarters paved, a total of 12 square miles. That's the equivalent of 22 Hyde Parks.

If that statistic sounds frightening, it's actually pretty good compared to the rest of the UK. Worst is the North East, with 47 per cent of front gardens under the hard stuff.

I'm sure the only reason the London figure isn't higher is because many properties in the capital don't have front gardens big enough to accommodate a bicycle, let alone a car. Because, let's face it, being able to park outside your own house - not something that is by any means guaranteed by residents' parking zones - is fantastically convenient. All that heaving around of toddlers, buggies, shopping or whatever is reduced to a minimum.

The downside is not just the resulting view of endless automobile rear ends and miles of concrete. It's not even the disappearance of the shrubs and trees that used to enliven the urban landscape.

According to the Royal Horticultural Society, which has just produced a very useful leaflet on the subject, hard standing for parking contributes to serious environmental problems, notably flooding.

A garden acts like a soakaway, absorbing rainwater through the soil, while surfaces such as concrete and paving can increase the amount of rainwater that runs off by an astonishing 50 per cent. In most UK cities, rainwater run-off is channelled through storm drains and out into rivers. In London, however, the sewage system handles the run-off. When the system becomes overloaded, the overflow of rainwater - along with the sewage - is discharged straight into the River Lee or the Thames. OK, it means your lavatory won't back up, but it doesn't do much for the fish.

Paving your front garden also has an impact on the local environment in your street. When I was a child, most front gardens had at least a privet hedge (Ligustrum ovalifolium with its pungent flowers), or a lawn, or a few roses. Many of these have now been swept away and the result is not only a lack of vegetation to help regulate urban temperatures, but an actual increase in those temperatures because hard surfaces absorb heat during the day and release it at night.

Finally, there's the potential effect on the structure of your house, especially if it is built on clay soil, which shrinks and swells as the water content varies throughout the year. Cover the soil with an impermeable blanket of concrete and it will receive very little moisture at all, with the result that it will shrink radically and your house will develop large cracks.

The RHS isn't suggesting that parking in your front garden should be banned. But it does point out that, while off-street parking can add thousands to the selling price of your home, buyers are much more attracted by leafy residential streets.

The solution, it says, is to use materials that allow rain to penetrate the ground below, such as gravel or permeable pavers. Ask yourself if you really need to pave the whole garden, or whether two paved tracks would be enough. And think hard about whether you can incorporate shrubs or hedges, which will provide food and shelter for wildlife as well as filtering the dust from the street.

The RHS leaflet has a whole host of further suggestions, including planting lists, design examples and a product guide, so if you're thinking of creating a parking space in your front garden, it's well worth getting hold of a copy.

The Front Gardens leaflet is available as a PDF file on the RHS website at www.rhs.org.uk/gardeningmatters, or send a 46p SAE to: Front Gardens leaflet, Advisory Services, RHS Garden Wisley, Woking, Surrey GU23 6QB