On the western edge of the city of Bristol is a nationally important site for wild plants. The Avon Gorge is home to over 500 plant species; as well as whitebeam trees which are found here and nowhere else on Earth, the gorge has two plant species – Round-headed Leek (Allium sphaerocephalon) and Bristol Rock-cress (Arabis stricta) – that are found nowhere else in Britain, and over twenty other nationally rare or scarce species. Peter Marren, in his book Britain’s Rare Flowers listed it as one of the top four sites in England, alongside Upper Teesdale, the Lizard in Cornwall, and the East Anglian Breckland. There can’t be many British botanists on whose bucket-lists a visit to the Avon Gorge doesn’t feature.
Given that I live fifteen minutes away by car from the gorge, you would have thought I’d spend vast amounts of time there each summer and would know the place inside out. In fact, I have tended to spread myself much more equally across the city’s wildlife sites, and so to date haven’t really given the gorge the attention it deserves. Now that I have this blog to write, something tells me that will change.
This afternoon I explored the Black Rocks area of the gorge, which is below the viewpoint on Bristol Downs called Sea Walls (see the map below for the location). The viewpoint is surrounded by sheer cliffs on three sides, but part-way down on the southern side, these give way to a limestone grassland slope with scattered rocky outcrops, altogether covering about a quarter of a hectare. I climbed the steep path which runs up the slope from the car park by the A4 Portway road. The photos at the top of this post show this part of the gorge viewed from the car park, and a close-up of a small part, to give you an idea of the species-richness of the grassland here.
Here are some of the plant species I photographed today. Going clockwise from top left, we have Basil Thyme (Clinopodium acinos), Common Rock-rose (Helianthemum nummularium), Bloody Crane’s-bill (Geranium sanguineum) and Fairy Flax (Linum catharticum).
Common Rock-rose and Fairy Flax are widespread species in limestone grassland sites around Bristol, By contrast, Basil Thyme, although found widely throughout the gorge, has been recorded at only one other site in Bristol, near Blaise Castle, and at only about five other sites surrounding the city, Slightly farther afield, it is more common in the Mendips, where its rocky limestone grassland is in greater supply, and also on the Cotswolds and Salisbury Plain.
Bloody Crane’s-bill is the rarest of these four species locally. Other than in the Avon Gorge, it is only found as a native species in Cheddar Gorge and in the Wye Valley, although it also occurs as a garden escape or a deliberate introduction in a handful of places. Unlike Basil Thyme, whose British range is centred on south-eastern England, Bloody Crane’s-bill is a more northern plant; Bristol is on the south-eastern edge of its native range in Britain.
Bristol’s new mayor, George Ferguson, has recently suggested that the Avon Gorge could be put forward to UNESCO as a proposed World Heritage Site, although interestingly, only on cultural grounds, because of the presence of the Clifton suspension bridge, rather than because of its natural features. Britain’s current suite of World Heritage sites only contains one location that qualifies under both cultural and natural criteria (the island of St Kilda off the northwest coast of Scotland), but I think a good case could be made for the Avon Gorge too. See what you think: the criteria are here.