ARC volunteer Gary Ritson explains why bare ground is so important when creating habitats to benefit a wide variety of species.

Bare ground is one of the hardest habitat features to create and maintain on any nature reserve but it can support a wide variety of animals and plants; some of our rarest fauna and flora rely on these bare ground features for part or the whole of their life cycles. Many organisms fill very narrow ecological niches and can have very precise habitat requirements. Bare ground needs to be present in many forms to fulfil these needs, from small patches to large machine dug traces. As Britain’s semi-natural habitats become increasingly stabilised, natural exposures of bare ground disappear and it’s up to reserve managers to create this much needed habitat element. ARC has been at the forefront of bare ground creation on heathlands for our target species the sand lizard but in this blog we will look at some of the other creatures which need bare ground to thrive.

Many invertebrate species are dependent on bare ground. One example you may have seen in the press recently is that of the great fox spider Alopecosa fabrilis – one of Britain’s largest spiders at two inches (5cm) wide. This arachnid was previously thought extinct after last being seen on Morden Bog in Dorset in 1999. The now critically endangered spider has recently been rediscovered on a MoD site in Surrey, with its presence interestingly being attributed to the availability of bare ground patches created by military exercises, which cause disturbance to the vegetation and prevent the succession of shrubs and trees. The spider uses the bare sandy patches to hunt other invertebrates like ants, beetles and small spiders, using an ambush-style hunting strategy.

Another threatened invertebrate is the endangered Purbeck mason wasp Pseudepipona herrichii which is found on only a few sites in Dorset and is one of the UK’s rarest invertebrates. These parasitic wasps need exposed ground with a nearby water source so they can build their nests, as well as exclusively requiring the presence of the heath button moth Acleris hyemana to feed to their young. Females excavate a shallow burrow in the substrate following mating, and then search out heath button moth larvae. These larvae are paralysed and stored in the burrow alive, whereupon eggs are laid and once hatched, the young will devour the larvae.

Purbeck mason wasp Pseudepipona herrichii	Great heath tiger beetle Cicindela sylvatica

The heath tiger beetle Cicindela sylvatica is yet another example and is one of Britain’s fastest beetles, with both adults and larvae being predatory, feeding on other invertebrates. The larvae are more generalist ambushing their prey from within their burrow but the adults require longer stretches of bare ground to chase after their prey. Due to loss of heathland habitat and diminishing quality of bare ground on surviving heaths, populations are in decline and it is now listed on the UK Biodiversity Action Plan.

ARC staff also recently noticed a species of mining bee (pictured right) on a cold and misty morning on an ARC site in the Isle of Purbeck . These solitary bees were observed nesting in their burrows on the natural bare ground present on small cliff sides where vegetation struggles to take root, and occasionally conducting slow and lazy flights, probably due to the cold temperatures.

As you can see, bare ground is extremely important for invertebrates, only a handful of which are mentioned here. ARC prides itself on not only preserving heathland habitat for amphibians and reptiles but for biodiversity as a whole, and it’s by maintaining the complex elements within a habitat that we hope to achieve this.