Warming impedes aquatic plant recovery via enhanced herbivory from insect outbreaks

Climate warming can destabilize ecological communities by altering species interactions. Population outbreaks, defined as rapid, exponential increases in population size within a given spatiotemporal scale, are naturally occurring phenomena with significant ecosystem-wide consequences. Such outbreaks are expected to increase in frequency under climate change, yet their ecological consequences under warming remain poorly understood. Here, we conducted a large-scale pond mesocosm experiment (48 mesocosms, each of 2500 L in volume) to show that warming significantly reduced the growth and impeded the regenerative capacity of aquatic plants following the outbreak of an aquatic moth (Parapoynx diminutalis). These effects were driven by warming magnifying herbivory, which substantially diminished the growth and recovery of macrophytes, leading to a turbid state dominated by phytoplankton. Our findings provide strong evidence that global warming can destabilize freshwater ecosystems under population outbreaks, risking the loss of basal resources that provide both food and habitat complexity. The cascading effects on the wider food web could lead to widespread loss of taxonomic and functional diversity, impairing essential ecosystem functions and services.