other wildlife. Ecology The steep walls of the gorge support some rare fauna and flora, including species unique to the gorge. There are a total of 24 rare plant species and two unique trees: the Bristol and Wilmotts's whitebeams. Other notable plants include Bristol rock cress, Bristol onion, spiked speedwell, autumn squill and honewort. Because of its steep sides, there are many parts of the gorge on which trees cannot grow, making way for smaller plants. The gorge is also home to rare invertebrate species. The gorge has a microclimate around 1 degree warmer than the surrounding land. The steep south-west facing sides receive the afternoon sunlight, but are partially sheltered from the prevailing winds. When winds come from the Bristol Channel in the north west they may be funnelled into the gorge, creating harsh and wet conditions. The steep gorge walls make an ideal habitat for peregrine falcons, with a plentiful supply of food nearby in the form of pigeons and gulls. Peregrines have a history of nesting in the gorge, but having become rare in the British Isles they did not breed and were rarely seen in the gorge after the 1930s. In 1990 Peregrines returned to the gorge, and have successfully bred in most of the following years. On warm days a strong uplift forms in the gorge, on which birds of prey soar while hunting. The gorge also houses large populations of Jackdaw and horseshoe bats, both of which find homes in the caves and bridge buttresses. Due to its geology and ecology, an area of of the gorge and surrounding woodland has been protected as a biological and geological Site of Special Scientific Interest (SSSI), the original notification taking place in 1952. The site may in future be protected as a Special Area of Conservation under the European Commission Habitats Directive (92/43/EEC). The Leigh Woods side of the gorge is largely owned by the National Trust. The Downs on the city side of the gorge are owned by Bristol City Council and managed as a large public park. The gorge side is protected in partnership with Bristol Zoo, WWF and English Nature. The council's management of the gorge involves balancing the need to protect its ecology with recreational uses such as rock climbing. Green-flowered helleborine is found on the western side of the gorge, in a wooded area next to the towpath below Leigh Woods.