Beautifully tended front gardens were once a source of pride and an indicator of the owners' social status, but they are increasingly being dug up and paved over to provide parking spaces.

The demise of the front garden has caused particular alarm among the organisers of the Chelsea Flower Show, who have launched a campaign to save them from being paved over.

The Royal Horticultural Society, which runs the show, is placing special emphasis this year on a front garden competition class.

Garden-grabbing — the practice of buying up a house with a garden and redeveloping it as flats or a mini housing estate — is one of the RHS's chief concerns. It is estimated that at least 30,000 gardens are lost to development every year, and on top of that many more front gardens are turned into parking areas, whether a stand for a single car or a gravel sweep with room for half a dozen vehicles.

There are fears that the loss of front gardens is changing the nature of urban Britain. In towns and cities, the area of land used as gardens and other green space can be crucial to the survival of wild animals and plants.

Bob Sweet, the show organiser, said: “We are concerned about the loss of gardens and particularly the loss of front gardens, usually for parking. It inevitably reduces the amount of greenery and the amount of biodiversity. We are concerned about the number being lost to all sorts of things — back gardens as well — as they get built on and concreted over.

“People are associating wildlife with their gardens more these days. It's not only about growing plants. The biodiversity issue is coming through very strongly.”

Using front gardens to park cars can, the RHS said, cause problems for the environment, because concrete and asphalt prevent water soaking into the soil. “It's not just the aesthetic loss of front gardens, it's contributing to flooding in risk areas,” Stephen Bennett, the RHS shows director, said. He called for homeowners who want to find car-parking space in front of their houses to consider alternatives to hard-standing, such as reinforced areas that still allow grass to grow through.

The loss of front gardens has doubled in intensity during the past decade. In 1997, 11 per cent of housing developments were on land already classified as residential, but by 2006 this had grown to 22 per cent. The problem was worst in the South East, where 32 per cent of new houses were on previously residential plots, compared with 16 per cent in 1997.

Guy Barter, the chief horticultural adviser at the RHS's principal garden at Wisley, in Surrey, said that the impact was greatest on properties with large, established gardens that were the most valuable for wildlife.

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