Brownfield sites promote biodiversity at a landscape scale.

Repurposing of brownfield sites is often promoted, because it is perceived that protecting the "green belt" limits damage to biodiversity; yet brownfield sites provide scarce habitats with limited disturbance, so conversely are also perceived to be ecologically valuable. Combining data from three national-scale UK biological monitoring schemes with location data on historical landfill sites, we show that species richness is positively associated with both the presence and increasing area of ex-landfill sites for birds, plants and several insect taxa. Assemblage rarity of birds is also positively associated with presence of ex-landfill sites. Species richness associated with ex-landfill sites declined over time for birds and insects but increased over time for plants. These findings suggest that development of brownfield sites may have unintended negative consequences for biodiversity, and imply that to minimise loss of biodiversity, brownfield site repurposing could be targeted towards smaller sites, or sites in areas with a high density of other brownfield sites.