The BUGS 2 project is a study of the environmental and biodiversity value of domestic gardens in urban areas, across five cities in the UK, carried out from 2004-2007. The project developed from work done in the previous BUGS project which examined the biodiversity value of gardens within a single city (Sheffield). BUGS 2, which is jointly funded by English Nature (now Natural England), the Countryside Council for Wales, Environment and Heritage Service (Northern Ireland), Scotland and Northern Ireland Forum for Environmental Research (SNIFFER), and the Department for Environment, Food and Rural Affairs widens the scope of this work to examine the diversity of plants in gardens and the resource that gardens provide for wildlife, in different parts of the UK.
The Project page gives some more detail about the project and the Results page summarizes the work done, and provides references for the published results, to date.
The BUGS project supports the recent Wildlife Gardening Manifesto produced by the The Forum for Gardening with Wildlife in Mind, which you can read more about on the Natural England website.