Climate change is accelerating the defoliation of forests, a crisis exacerbated by the spread of invasive species like the spongy moth. New research conducted by the University of Chicago and Argonne National Laboratory reveals that rising temperatures and drier conditions will weaken natural defenses against these pests, increasing the damage they inflict on North American forests.
The study, published in Nature Climate Change, highlights how the interconnectedness of species amplifies the effects of climate change. “The vast majority of previous studies focus on individual organisms,” explained Dr. Greg Dwyer, Professor of Ecology and Evolution at the University of Chicago. “But small climate changes can ripple through ecosystems when compounded across multiple species.”
Native to Europe, the spongy moth (Lymantria dispar) has wreaked havoc on North American hardwood forests since its accidental introduction in Massachusetts in 1869. These moths spread quickly as their eggs are transported on surfaces like firewood and outdoor furniture. Their caterpillars devour tree leaves, particularly those of oak trees, leaving vast areas of forest defoliated and vulnerable to further damage.
For decades, forests suffered heavy losses until the arrival of the Entomophaga maimaiga fungus, a pathogen from Japan that infects and kills spongy moths. First observed in 1989, the fungus has been an effective, natural check on moth populations, especially in cool, moist climates. However, this delicate balance is now under threat.
Dwyer’s team developed advanced computer models incorporating climate projections to analyze how environmental changes impact the interaction between spongy moths and their natural controls. Their findings are concerning. As hotter, drier conditions become more prevalent, the fungus E. maimaiga will struggle to thrive, reducing its ability to control moth populations.
This decline could trigger more frequent and severe spongy moth outbreaks. Even slight reductions in the moth’s mortality rates lead to explosive population growth and increased defoliation. Compounding the problem, another natural pathogen, the nucleopolyhedrovirus (NPV), requires large moth populations to spread effectively, leaving forests increasingly defenseless.
While predictions indicate severe defoliation in the coming decades, signs of this shift are already apparent. Recent years of below-average rainfall and above-average temperatures have sparked unexpected spongy moth outbreaks, confirming the models’ accuracy sooner than anticipated.
This research underscores the urgent need for climate-informed forest management strategies. By acknowledging and addressing the interconnected impacts of climate change on ecosystems, scientists and policymakers can better safeguard forests from invasive species and the cascading effects of a warming world.
