1. National and international forest biodiversity assessments largely rely on indirect indicators, based on elements of forest structure that are used as surrogates for species diversity. These proxies are reputedly easier and cheaper to assess than biodiversity. Tree microhabitats – tree-borne singularities such as cavities, conks of fungi or bark characteristics – have gained attention as potential forest biodiversity indicators. However, as with most biodiversity indicators, there is a lack of scientific evidence documenting their...