Biodiversity 2020 identifies air pollution as a direct threat to biodiversity in England. Many habitats of nature conservation importance in the UK are adapted to low nutrient conditions and/or are vulnerable to acidification, and are sensitive to additional airborne nitrogen oxides (NO]~x~), sulphur dioxide (SO]~2~) and ammonia (NH]~3~), as well as to nitrogen deposition and acid deposition.
Pollutants come from a range of different sources, but transport is known to be the single largest source of NO]~x~ emissions. Natural England commissioned a study to assess what risk air pollution from roads poses to the SSSI and Natura 2000 network in England.
The objective of the literature review is to provide an addendum or update to the comprehensive review of ecological effects of diffuse air pollution from road transport on semi-natural habitats that was undertaken by Bignal and others in 2004.