Over the last 50 years, the human population of the UK (Britain and Northern Ireland, excluding overseas territories) has both expanded and become substantially more urbanised. The consequences for wildlife have undoubtedly been complex, with the low priority that has been given to monitoring schemes in urban environments compounding the difficulty in drawing overall conclusions. Nonetheless, it is clear that substantial areas of natural and semi-natural habitats have been lost, and that the richness and abundance, particularly of more specialist and previously narrowly distributed species associated with these habitats, have declined. Conversely, some more generalist species have greatly benefited, as have others that could exploit some of the more novel environments occurring in urban areas. Moreover, urban areas have become more significant for wildlife over the past 50 years, in large part because they figure more prominently in landscapes, because of a marked increase in awareness of and conservation efforts for urban biodiversity, and because urban areas hold a substantial proportion of the national populations of some species that have experienced dramatic declines in the wider countryside.