Logging and wood harvesting have by far the largest impact on both threatened and non-threatened saproxylic beetles, affecting 35 out of 75 threatened species and 232 species in total.
Agriculture expansion and intensification and urban sprawl are the next most important threats, impacting on 25 and 26 species, respectively. Other threats include forest fires and fire suppression.
Also of considerable significance is the lack of understanding and of consideration of the habitat needs of saproxylic beetles by most conservation professionals and resources managers. Saproxylic organisms depend on the dynamics of tree aging and wood decay processes, which in turn have implications for land management – non-intervention or minimum intervention in former wood pasture can kill, and prevent the renewal of, old trees and can therefore be very damaging; livestock grazing can also be essential to maintain adequate habitats.
The other key overarching threat is global climate change caused by greenhouse gas emissions, the impacts of which on saproxylic beetles will be very difficult to predict. Saproxylic beetles depend ultimately on living trees and, given climate change predictions for major changes in the European ranges of tree species, questions arise about the limited mobility of many of our already threatened old growth beetles and the already fragmented landscapes in which they live. Will it be possible for such species to colonise newly available habitats? It is impossible to offer any meaningful predictions at this stage. While in the short-term, increases in the availability of dead wood as trees decline in response to increasing temperatures and incur damage from increased storminess, the long-term prognosis is not good. Many of our more threatened species are known to be warmth-loving under present conditions and so may be expected to increase in abundance in the short term, but, if the temperature predictions are correct, these beetles too may be expected to decline at site level as temperatures continue to rise.
The above are broad and long-term threats but there are also more short-term and localised threats arising from - often ill-informed – sanitation and forest hygiene objectives, as well as – often misconceived – safety constraints in areas well-used by people, where old trees and dead branches are often automatically removed without any serious assessment of the actual threat levels involved.
The threats for a total of 86 saproxylic beetles remain unknown.
Information has not been collected during the assessment process on the relative importance of one threat compared to another for a particular species. Development of such information in the future is a priority for the assessment and will enable a more complete analysis of significant threats to species.