Protect the Cavities, Please!

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Science  17 Jun 2011:
Vol. 332, Issue 6036, pp. 1360
DOI: 10.1126/science.332.6036.1360-c

Many vertebrate species that live in forests depend on tree cavities for nesting and shelter. Only a small proportion of these cavity-dependent species, however, actually excavate holes in trees. These species are thus dependent on either the few excavating species, mostly woodpeckers, or decay to create the cavities. This has led to the prioritization of protection for cavity excavators in the hopes of mitigating the impact of the harvest of large old trees, in which decay-created cavities are found. Cockle et al. looked at the use of excavated and nonexcavated cavities and at cavity persistence across continents and found striking differences among regions. Woodpeckers were responsible for a large proportion of functional cavities in North America, and these tended to persist over time. In contrast, most cavities used for nesting or shelter in Europe and South America were created by decay, and those that were excavated actively were short-lived. In Australia and New Zealand, all cavities are created by decay, a process that may take over 200 years. These results suggest that cavity excavators may be able to ameliorate some impacts of tree harvest on cavity-nesting species in North America, but that this approach will not work in other regions.

Front. Ecol. Environ. 9, 10.1890/110013 (2011).

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