Retention forestry as a major paradigm for safeguarding forest biodiversity in productive landscapes: A global meta-analysis

Currently, there is an increasing need for sustainable forest management to meet multiple beneficial social and ecological goals. This has spurred the emergence of retention forestry, which aims to maintain key elements of the stand during harvesting to ameliorate the post-logging structure over forest generations. Despite the global expansion of this approach as a conservation tool in production forests, quantitative evaluations of its effectiveness are still lacking, particularly for comparisons across different biomes, different levels of economic development, and different taxa. We conducted a meta-analysis to identify the general responses of forest species to the set-aside actions (i.e., retaining the important biotic and abiotic features during logging to conserve biodiversity). We found that retention forestry can preserve a degree of species richness equivalent to that of primary forests, at least at the stand level. This potential does not differ among regions or economic development levels, supporting the ecological meaning of retaining “biological legacies” over forest generations irrespective of forest biomes. Despite their common focus on biodiversity conservation, retention forestry is different from the reduced-impact forestry that is implemented with selective logging. The reason for this difference is that the former and the latter approach focus on what is retained and what is logged during harvesting operations, respectively. Thus, our meta-analysis also focused on comparisons between these two logging methods based on different viewpoints, i.e., from the species perspective vs. the perspective of human needs. We found that although selective logging was not detrimental to forest taxa, retention forestry was more effective in conserving biodiversity. We thus argue that the principles underpinned by retention approach, such as the consideration of natural disturbance regimes, and the provision of important habitats for species, will be essential overall for biodiversity-oriented forestry. Retention forestry will continue to play a fundamental role in encouraging further development of management schemes that have multiple goals.