Protecting the forests while allowing removal of damaged trees may imperil saproxylic insect biodiversity in the Hyrcanian Beech Forests of Iran
The 1.8 million ha of forest south of the Caspian Sea represent a remarkably intact ecosystem with numerous old-growth features and unique species assemblages. To protect these forests, Iranian authorities recently passed a law which protects healthy trees but permits the removal of injured, dying and dead trees. To quantify the biodiversity effects of this strategy, we sampled saproxylic beetles and true bugs in 24 plots across the entire altitudinal gradient of Oriental beech. The composition of these communities as well as their overall richness and the richness of endemic and old-growth indicator species were best explained by dead wood volume compared to other environmental variables. Due to the striking evidence that dead wood is the major driver of saproxylic diversity in these forests, we urge Iranian authorities to reconsider their law, redirecting logging toward healthy medium sized trees. Otherwise, a major loss in biodiversity, similar to that experienced in European beech forests, can be expected.