Private gardens habitat statement

For the purposes of this statement, gardens are defined as the private open space surrounding residential dwellings, with the householder having sole responsibility for management. This statement does not include communal open space surrounding residential dwellings, as this is usually managed by an outside agency - a contractor employed by a local authority or private landlord for example.

An analysis of aerial photographs of Greater London undertaken by the London Ecology Unit in 1992 suggests that the gardens of private dwellings comprise about 20% (31,600 ha.) of the city's surface area.

Naturally, not all gardens will be of equal importance in terms of nature conservation value. The majority of gardens in areas of high-density housing are small plots with very little diversity (or opportunities to promote diversity) in vegetation structure. At the other end of the spectrum are the gardens of houses in some of the more exclusive parts of suburban London. These contain small pockets of woodland, ponds and other features which might well be managed as nature reserves in their own right if they were in the public domain. However, most gardens, particularly in suburban London, probably consist of the archetypal lawn with flowerbeds and borders, often with a fringe of semi-mature trees or hedgerow shrubs at the boundaries. Garden biodiversity is dramatically increased where a number of larger gardens adjoin each other, where features such as mature trees have been maintained within gardens or where ponds have been created.

The most important threat to the biodiversity of gardens is a lack of appreciation of its importance in the conservation of London's wildlife. Although a great many members of the public manage their gardens with wildlife in mind, most probably do so for aesthetic reasons rather than as a concerted effort to conserve biodiversity. Cutting hedgerows and shrubs during the bird breeding season, removing leaf-litter, dead wood and other organic detritus which harbours a variety of invertebrates and over-tidying can reduce wildlife value. Replacing soft surfaces with hard surfaces, by creating off-street car-parking in front gardens for example, has resulted in a major loss of vegetation in some areas.

Reduction in garden size resulting from backland development and infilling also significantly reduces the biodiversity interest of gardens. Backland development and infilling invariably results in the reduction of mature tree cover, overgrown shrubberies and old lawns, thus dramatically reducing the structural diversity provided by older, larger gardens. The use of chemical pesticides in gardens may also pose a threat to non-target species. It has been suggested that the decline in the national population of song thrushes, for example, may be partly linked to the use of molluscicides on farmland and in gardens.

Forms of gardening that express the aspirations and character of the gardener are becoming increasingly popular. Gardeners are 'designing' their outdoor space in much the same way as interior space is designed to fulfil personal tastes and preferences. One such gardening trend is the desire to make the garden wildlife-friendly, particularly by people who want to actively express environmental concern. Gardening for wildlife can be linked to other environmental issues such as reduction in water use, planting trees and shrubs as filters of noise and air pollution, and growing organic produce.

Gardens form a vast and intricate network of green corridors which can facilitate the movement of certain species between adjacent areas of open space and which can support populations of common woodland edge species. By identifying where mature garden habitats might provide such links, areas of open space with little existing nature conservation interest can be targeted for enhancement.