Biological control protects carbon sequestration capacity of plantation forests

In many natural and managed forest and tree systems, pest attacks and related dieback events have become a matter of increasing global concern. Although these attacks modify the carbon balance of tree systems, their contribution to climate forcing and the relative impact of nature-based mitigation measures is seldom considered. Here, we assess the extent to which biological control protects or reconstitutes carbon sequestration capacity and storage in monoculture tree plantations globally. Specifically, we draw upon field-level assessments, niche modeling and forest carbon flux maps to quantify potential risk of carbon sequestration loss due to three globally important insect herbivores of pine and eucalyptus. Specifically, herbivory by the tree-feeding insects Sirex noctilio, Leptocybe invasa and Ophelimus maskelli conservatively reduces carbon sink capacity by up to 0.96–4.86% at the country level. For a subset of 30, 11 and nine tree-growing countries, this potentially compromises a respective 4.02%, 0.80% and 0.79% of the carbon sink capacity of their tree hosts. Yet, in the invasive range, released biological control agents can help regain lost sink capacity to considerable extent. Equally, across both the S. noctilio native and invasive range, carbon sequestration capacity is protected by resident biota to the tune of (max.) 0.28–0.39 tons of CO2 equivalent per hectare per year. Our exploratory valuation of pest-induced sequestration losses and their biodiversity-driven mitigation informs climate policy, biosecurity, and management practice.