Tree damagers: a unified framework for categorizing and examining the ecological role of non-human vertebrate tree damaging species

Background/Question/Methods

Dead and decaying trees are used by a wide range of species during their life cycle and are a foundational structural element of forest ecosystems. The decay process is often thought to be caused primarily through a combination of senescence and fungal or insect invasion, but many non-human vertebrates also modify trees, which can accelerate this process. While previous research has investigated, for example, the economic costs of bear damage or the importance of primary cavity excavators, we are unaware of work to unify these into a single framework of non-human vertebrate tree damage. To explore and describe the extent of this key functional role, we conducted a global, systematic literature review to identify non-human vertebrate tree damagers. We categorized the types of damage and approaches to measuring damage across individual, population, and community levels. For vertebrates in North America, we summarized spatial patterns of damager richness across ecoregions and in relation to forest cover.

Results/Conclusions

We found that non-human vertebrates that modify trees are found extensively in forest ecosystems, and that trees are damaged from the roots to the buds, with consequences for many other species that rely on damaged trees. While non-human vertebrates that damage trees have often been persecuted for the resulting economic damage, we suggest that these species can play an important role in restoring degraded forests to more structurally complex, and therefore biodiverse, communities.