Insects & pathogens eat into our (carbon) savings
Quirion BR, Domke GM, Walters BF, Lovett GM, Fargione JE, Greenwood L, et al. (2021). Insect and Disease Disturbances Correlate With Reduced Carbon Sequestration in Forests of the Contiguous United States. Front For Glob Chang. 4:1–10. PDF.
Summary
Forests offer a powerful natural climate solution by sequestering carbon. Invasive insects and diseases reduce this carbon storage capacity. However, few studies have quantified the extent to which insect pests and pathogens undermine the ability of forests to mitigate climate change. Quirion et al. (2021) used the Forest Inventory & Analysis plot network, spanning the continental United States, to quantify whether and how much carbon sequestration is reduced by insects and diseases. By evaluating plots that were measured twice within the period 2001-2019, they identified forested plots with damage to at least 25% of the trees or loss of at least 50% of an individual tree species between measurements. Compared to plots with no recent disturbance, they found that plots affected by insect disturbance sequestered an average of 69% less carbon, and plots affected by disease disturbance sequestered an average of 28% less carbon.
Take home points
Insects and pathogens collectively reduced the annual C sequestration capacity of forests by an estimated 12.8 teragrams of carbon. This represents approximately 9% of the contiguous US’s total annual forest C sequestration and is equivalent to the carbon dioxide emissions from over 10 million passenger vehicles driven for one year.
Losses from insects and diseases are likely even higher than estimated, since small disturbances (affecting <25% of the trees in a plot or less than one acre) were not included in the analysis.
This paper focuses on lost C sequestration capacity by live trees, which builds on the research summary of Fei et al. 2019 (that paper focused on tree mortality from a specific suite of invasive insects).
Management implications
Reduce introductions of new pests and pathogens using the Tree-Smart Trade suggestions from Lovett et al. 2016 (research summary here).
Evaluate the potential of improved forest management, such as encouraging mixed-age and biodiverse stands, and forest thinning, to reduce the impacts of insect and disease disturbance on forest carbon sequestration capacity. The efficacy of these treatments depend on the insect or disease, and the context of the site.
Keywords
Changing biotic interactions, impact studies, forest, natural climate solutions, insect, pathogen, climate change mitigation