DEFRA have recently published the definition and mapping of open mosaic habitats on previously developed land.

"Open Mosaic Habitats on Previously Developed Land (OMH) was included in the new list of UKBAP Priority Habitats and species in 2007. OMH Priority Habitat represents a diverse range of sites, largely because of the range of previous land uses associated with the sites, which include coal mining, industry and housing. This habitat is concentrated in, but not confined to, urban and former industrial landscapes.

The biodiversity value of these sites is often underestimated. The habitat supports many species and some habitat types that are a priority for nature conservation, such as pioneer communities and flower-rich grasslands. The areas have been described as important habitats for many UK BAP prority species or Red Data Book/List species.

These habitats are at substantial risk of destruction and serious degradation from a number of factors, including urban development, landfill, unsuitable reclamation, eutrophication, lack of appropriate management and succession. Few previously developed sites have SSSI protection and creation of new sites is limited.

Although there are inventories of previously developed land, these do not distinguish those sites which support the Priority Habitat. A clear definition of this habitat type is essential to enable transparent planning guidance because of the Government's commitment to construction of housing developments on brownfield land. There is therefore a need to identify and map potential sites and to inform survey, assessment and evaluation allowing the compilation of a national inventory of the Priority Habitat. This will help to inform Defra, the devolved administrations, appropriate agencies, NGOs and Local Authorities regarding the conservation management of the Priority Habitat and its associated species. At a local level, this will also enable Planning Authorities to identify brownfield sites which are important for biodiversity when considering development proposals, and to determine any appropriate mitigation measures".

Whilst we don't currently have any targets for this habitat in Berkshire, we will seek opportunities to help conserve and enhance these important wildlife habitats.

Buglife have lots of additional information on why Brownfield sites are so important for invertebrates.