Centrally positioned within the Avon area and influenced by the ecologically rich landscapes described above, Bristol supports a surprising diversity of wildlife. Indeed the city was at the forefront of the urban nature conservation movement, and continues to be a major focus for the Trust through the Bristol Wildlife Project , which is run in partnership with Bristol City Council.

A wide range of wildlife sites can be found in Bristol - from the large estates on the edges (such as Ashton Court, Blaise Castle and Stoke Park), to numerous 'green spaces' dotted throughout the city (including parks, gardens, allotments, cemeteries and sports grounds). Important areas of woodland have survived the urban sprawl, for example Badocks Wood, while notable grassland sites include Hawkfield Meadows, Troopers Hill, and the Downs. The rivers Avon, Frome and Trym form important wildlife corridors, as well as wetland habitats in themselves, supporting invertebrates, fish and birds. Lawrence Weston Moor is the only true remaining area of marshland in the Bristol area, while Avonmouth Sewage Treatment Works provides a stopover for many species of wildfowl within a heavily industrial area.

Wildlife can be found in even the most built-up parts of the city, for example on derelict land, road verges and railway embankments. Buildings can support bats and nesting birds, while up to eight species of fern have been recorded growing on walls in the Bristol area.