Saproxylic beetles are insects that depend on dead and decaying wood for at least part of their lifecycle, and play important ecological roles in European habitats. Together with fungi, they contribute to the break-down of deadwood and are involved in decomposition processes and the recycling of nutrients in natural ecosystems. They 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, and some species are involved in pollination.
In Europe, there are 58 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. Dead and decaying wood offer 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, while 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 age structure, total number of trees, varying tree density, and habitat continuity. The assemblage 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.
The long-term survival of these beetles depends on new generations of trees developing and becoming suitable for colonisation as the host trees decline and disintegrate. This means that certain beetles can be at risk even while the overall population is strong, as new host trees are not becoming available. Old and hollow trees have become increasingly scarce around the world, including in Europe, due to land management practices.
Much is left to learn about the saproxylic beetles of Europe. 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.