Suitable sources of disturbance include landslips, wind and salt blast on sea cliffs, sand accretion on sand dunes and small-scale poaching by grazing animals. Disturbance as a result of direct human activity can also produce good habitat, both in semi-natural situations (such as footpaths and tracks on heathlands) and in brownfield contexts, although much depends on the scale and frequency of such human-caused disturbance (small-scale, patchy disturbance is more likely to produce good invertebrate habitat than large-scale and more homogeneous disturbance).
Semi-natural systems supporting important examples of this assemblage type include heath grassland, moorland, hay meadows, scattered scrub and woodland edge. Sward height and density is often an important factor in species representation, as are the extent of flowering and seed-set.
Many species develop in specific microhabitats, some of which are mostly or entirely restricted to mature trees. Many of the rarest species are dependent on the presence of ancient trees, whose age can be measured in centuries. For these species, the rarity and isolation of prime habitat in the modern landscape makes colonisation of new sites all but impossible.
The epiphyte fauna includes grazers of algae, lichens and mosses on the surface of trunks and branches, as well as their predators and parasites.