These sandstone rocks were probably formed in the last glacial period of the Ice Age 20 to 50,000 years ago though the actual sand would have been deposited in a river system during the Cretaceous Period approximately 138 million years ago. They are characterised by large boulders and vertical joints which are widened through ongoing weathering and movement, some of which are now just about wide enough to squeeze through. The rocks themselves have developed a hardened crust which helps protect them from the weather and shows some characteristic types of weathering including strange small hollows known as honeycomb weathering and polygonal cracking on the rounded tops of the rocks. The base of the rocks is often undercut to form overhangs and rock shelters. Archaeological investigations of some of these rock shelters at Eridge produced many struck flints of Mesolithic date and even some late Iron Age/early Romano-British smelting. As these flints were small and not of local origin it is thought that raw flints were transported into the area and then made into tools and weapons suggesting the rock shelters were used temporarily by a small group of mobile hunter gatherers as has been found in similar locations in the Weald.
Eridge Rocks is designated as a Site of Special Scientific Interest for its lower plant interest, the mosses, lichens and liverworts. Many are so called oceanic species – species normally associated with the mild oceanic climate of Western Britain rather than South East England, but are able to thrive here in the mild, damp semi-shaded environment that the rocks provide. One of the specialities of the rocks is the Tunbridge filmy-fern, so named as it was first discovered on the High Rocks at Tunbridge Wells in the 17th century. It is found in just a couple of locations at Eridge Rocks but surveys in 2016 found that it had recently colonised a few new areas of the rock face.
When Sussex Wildlife Trust bought the reserve in the late 1990s, the rocks were almost completely obscured by rhododendron. This was planted by the Victorians along with bamboo and acacias to landscape the area. At this time the rocks were quite famous and well visited and there are descriptions of elaborate dinner parties taking place with liveried footmen attending at the bottom of the rocks.
Unfortunately by the time Sussex Wildlife Trust bought the rocks the rhododendron was casting deep shade over most of them and there was concern about the welfare of the lower plants. It is generally considered that light dappled shading is what the lower plants require. We therefore undertook a project to remove the rhododendron in conjunction with a rigorous monitoring programme to assess the effect on the lower plants. The monitoring programme has proved very informative with many plants thriving in the dappled shade.
The lichen Bunodophoron melanocarpum a species thought to have been lost to shade at Eridge, had survived and is now expanding. The liverwort Harpanthus scutatus which had not been seen at Eridge since 1952 was recorded from a single quadrat in 2004 and continues to spread. Some of the other specialities at Eridge Rocks include the lichen Cladonia caespiticia a rare species on rocks and is very rare in Sussex but present in at least three locations at Eridge; the mosses Dicranum scottianum and Orthodontium gracile, and the leafy liverwort Bazzania trilobata.
The monitoring has observed that there is some kind of community succession sequence amongst the bryophytes themselves, as heavier growth of some of the larger species leads to eventual peeling of the plant mat and a renewal of the bare substrate for some of the first colonisers, often the lichens.
Today we manage the rocks by maintaining the appropriate levels of dappled shade and shelter through an ongoing programme of coppicing at the foot of the rocks, crown lifting some of the overhanging holly and yew branches and keeping bramble under control. Much of this work is carried out with the help of volunteers but due to the dangerous nature of working near the top of the rocks, tree surgeons with climbing qualifications are called in to assist.
The rocks are a well-known spot for climbing. We work in conjunction with the British Mountaineering Council to allow their members to climb in certain areas. The really rich areas for lower plants are off limits and there is a special code that climbers must abide to when climbing on any sandstone rocks to protect the rocks themselves.
Although the rocks are the most obvious feature of the nature reserve, there is much else to discover. The rocks are surrounded by woodland, a mix of sweet chestnut coppice and birch scrub with occasional ash and hazel with alder along the stream. In the spring, the floor is covered with bluebells and birdsong is heard everywhere. Migrants such as chiffchaffs and willow warblers join resident nuthatch and treecreepers. Lesser spotted woodpeckers are seen on occasion. In the woodland and at the base of the rocks are a number of veteran trees of both oak and beech – large old, open grown trees that support an amazing invertebrate fauna, particularly the saproxylic or dead wood insects. Surveys in 2011 discovered over 195 species of invertebrate including many rarities such as the beetle Oxylaemus variolosus. More obvious to the casual visitor are some of the longhorn beetles such as Leptura quadrifasciata or the wasp beetle Clytus arietis. We manage the woodland through small scale coppicing particularly around the veteran trees, the widening of rides to create warm open sunny areas and short rotation of the scrub along the paths. These all result in warm sunny conditions for bees, butterflies and other insects looking for nectar sources.