When to let a dead tree lie

It’s often argued that logging trees killed by insects or diseases is beneficial for forests—but evidence is mounting that it causes long-term ecological disruption.

The latest findings come from Białowieża Forest, a 550-square-mile woodland that straddles Poland and Belarus. It’s one of the few places in Europe where natural cycles of wind, fire, and disease still shape a forest at landscape scales. However, salvage logging after bark beetle outbreaks has altered the potential for natural generation according to a new study in the journal Biodiversity and Conservation.

The forest is set on a new trajectory that inevitably leads to the homogenization of the forest. Several years later, the herb layer in logged sites was dominated by disturbance specialists rarely found within the intact forest. The previous herb layer was largely destroyed by machinery or withered in the suddenly intense sunshine. Their seeds did not sprout. When beetle-killed trees were left alone, though, the original herb layer regrew. Dead trees provided necessary shade; their fallen trunks and branches created pockets of protection from grazing.