CONSERVATION & ECOLOGY


Saproxylic beetles


Dead wood is dead good


There’s a saying amongst ecologists and entomologists that ‘dead wood is dead good’, which refers to the importance to wildlife placed on seemingly decaying and redundant areas of woodlands. Peter Britton looks at that ‘ugly’ bunch of insects that provide an important role in local habitats far beyond their size


Together with fungi, they contribute to the breakdown of dead wood and are involved in decomposition processes and the recycling of nutrients in natural ecosystems. Saproxylic beetles interact with other organisms such as mites, nematodes, bacteria and fungi, assisting in their dispersal across the landscape. They also provide an important food source for birds and mammals, whilst some species are involved in pollination. In Europe, there are fifty-eight families of beetles (order Coleoptera) with nearly 29,000 species. The exact number of saproxylic species is unknown, but a database of French saproxylic beetles includes 3,041 species. According to expert opinion, there may be closer to 4,000 saproxylic beetle species in Europe. In the UK, the figure is thought to be in the region of 800.


S Dead wood is dead good


Dead and decaying wood offers a large variety of microhabitats, and different saproxylic species have evolved to exploit these niches, with certain species having very specific ecological requirements. Some saproxylic beetles require live old trees with cavities for their larval development, whilst others are dependent on trees that have recently died. Saproxylic beetle richness depends on the quantity and quality of available dead and decaying wood in any environment with trees and woody shrubs, as well as on tree


116 PC June/July 2020


aproxylic beetles are insects that depend on dead and decaying wood for at least part of their life cycle and play important ecological roles in our habitats.


age structure, total number of trees, varying tree density and habitat continuity. The diversity and numbers of saproxylic beetles can be influenced by the degree of sun-exposure, frequency of habitat disturbance, i.e. forest fires or clear-cutting, hedgerow management, clearance of fallen deadwood from parks, age of tree stands and presence of certain types of wood- decaying fungi, among others.


Threats


The main identified long-term threats are habitat loss in relation to logging and wood harvesting, and the decline of veteran trees throughout the landscape, as well as lack of land management targeted at promotion of recruitment of new generations of trees. More short-term and localised threats arise from sanitation and removal of old trees due to safety constraints, in places heavily influenced by humans, e.g. a golf course or park. Other threats include agricultural expansion and intensification, urbanisation, fires and climate change. Much is left to learn about the saproxylic beetles. In comparison with other species groups, and despite all the efforts of generations of entomologists, the biology of many species is still poorly known. Any research on saproxylic beetles enhances our knowledge of the functioning of ecosystems in wooded landscapes. One of the most valuable attributes of any golf club, woodland area or parkland is the species that are directly or indirectly dependent on dead, old and decaying wood. Veteran trees provide nutrition, shelter and anchorage to a whole ecosystem of species and the richness of species a tree


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