Open Mosaic Habitats on Previously Developed Land (OMH) are found mainly in urban and formerly industrial areas and have high biodiversity value. This value includes rare plants, mosses, lichens and a large number of rare invertebrates, especially bees, wasps and beetles. Between 12% and 15% of all nationally-rare and nationally-scarce insects are recorded from OMH sites. One of the other key features of OMH is the unusual groups of plants present; combinations which are often unique to OMH and currently little studied.

Because of the biodiversity importance of OMH the habitat was identified as a Biodiversity Action Plan habitat in 2007. However, such sites are threatened by redevelopment (due to their usual status as brownfield sites), inappropriate ‘restoration’, inappropriate management or natural succession. There is very little knowledge of the distribution of OMH, as there is no data that identifies OMH sites at a national level.

exeGesIS were awarded this project in 2011, which has increased understanding of OMH in England and Wales by identifying the key features that are found within such habitats and enhancing knowledge of the distribution of such sites. This involved the development of a new survey methodology and a survey of 98 survey sites to identify OMH habitat, as well as a survey of invertebrates on 50 of the sites - the largest single survey of its kind in the UK. These surveys provided invaluable information on the importance of OMH sites to conservation and the recognition of important sites remotely and in the field.

The results of this work were:

• A handbook for the identification and survey of OMH sites.
• A provisional national inventory of OMH sites in England and Wales, along with an inventory data capture rule base.
• An integrated OMH survey website, including a map of OMH sites and survey data entry forms.
• Field survey data supplied to the NBN Gateway.

Further information from Crispin Flower.