Are current management recommendations for saproxylic invertebrates effective? A systematic review

Conservation management recommendations for saproxylic invertebrates advocate the continuous provision of the dead and decaying wood microhabitats that they require for survival. Accepted site-based management practices include leaving fallen dead and decaying wood in situ, providing supplementary coarse woody material (CWM), inducing decay in mature trees and strategic planting in order to maintain a balanced age structure of trees in both space and time. Here we examine the empirical evidence regarding the effectiveness of such interventions using rigorous systematic review methodology. Systematic searching yielded 27 studies containing pertinent information. The evidence presently available is insufficient to critically appraise the utility of any specific intervention for conserving saproxylic species, or assemblages, in the long-term. However, there are a range of studies, conducted over relatively short periods of time, which do describe changes in saproxylic fauna in response to management practices. In the absence of robust, high quality evidence, recommendations relating to the use of specific site-based conservation interventions should only be regarded as speculative. Nonetheless, general proposals for the maintenance of suitable microhabitats, such as the protection of veteran trees within the landscape, are based on sound ecological principles and should be encouraged even though experimentally controlled and replicated evidence is lacking. Further primary research and long-term monitoring are required to fill the gaps in our ecological knowledge that potentially weaken the case for the effectiveness of current saproxylic invertebrate conservation action and would enable practitioners to make better informed decisions with regard to dead wood protection and provision.