Raffa, Kenneth F., Aukema, Brian H., Bentz, Barbara J., Carroll, Allan L., Hicke, Jeffrey A., Turner, Monica G., Romme, William H.


Published date June 1, 2008

Cross-scale Drivers of Natural Disturbances Prone to Anthropogenic Amplification: The Dynamics of Bark Beetle Eruptions

  • States that biome-scale disturbances by eruptive herbivores provide valuable insights into species interactions, ecosystem function, and impacts of global change
  • Presents a conceptual framework using one system as a model, emphasizing interactions across levels of biological hierarchy and spatiotemporal scales
  • Looks at bark beetles, which are major natural disturbance agents in western North American forests
  • States that recent bark beetle population eruptions have exceeded the frequencies, impacts, and ranges documented during the previous 125 years
  • States that extensive host abundance and susceptibility, concentrated beetle density, favorable weather, optimal symbiotic associations, and escape from natural enemies must occur jointly for beetles to surpass a series of thresholds and exert widespread disturbance
  • States that eruptions occur when key thresholds are surpassed, prior constraints cease to exert influence, and positive feedbacks amplify across scales
  • States that climate change and reduced habitat heterogeneity increase the likelihood that key thresholds will be exceeded, and may cause fundamental regime shifts
  • Concludes that systems in which endogenous feedbacks can dominate after external forces foster the initial breach of thresholds appear particularly sensitive to anthropogenic perturbations