Responses of insect pests, pathogens, and invasive plant species to climate change in the forests of northeastern North America: What can we predict?

Dukes, J. S., Pontius, J., Orwig, D., Garnas, J. R., Rodgers, V. L., Brazee, N., ... & Ehrenfeld, J. (2009). Responses of insect pests, pathogens, and invasive plant species to climate change in the forests of northeastern North America: What can we predict? This article is one of a selection of papers from NE Forests 2100: A Synthesis of Climate Change Impacts on Forests of the Northeastern US and Eastern Canada. Canadian Journal of Forest Research, 39(2), 231-248. PDF.

Summary

Climate change is predicted to raise Earth’s temperatures, alter precipitation patterns, and increase the frequency of extreme events. In northeastern forests, these alterations are expected to have a profound impact on invasive plant, pathogen, and insect species. This paper discusses the potential for future climate scenarios to support increases in range and impact on northeastern forests for two invasive plants (glossy buckthorn and oriental bittersweet), two pathogens (armillaria root rot and beech bark disease), and two forest pest species (hemlock wooly adelgid and forest tent caterpillar). While much evidence suggests expanded range and increased negative impact, the complexity of natural systems and climate models leads to high degrees of uncertainty for predicting how climate will impact northeastern forest species. Therefore, future research should focus on whole system analysis, and future management decisions should be made that allow for high degrees of uncertainty.

Take home points

• Temperature and precipitation changes

  • warmer temperature leads to increased survival and fecundity of plants and insects, and increased herbivory by insects

  • the impact of changing climate on pathogens is unclear; however, evidence suggests pathogens reach epidemic levels within a small range of climate conditions, so increasing temperatures might not necessarily lead to greater infection rates

  • less extreme winter temperature might allow populations to overwinter, thereby increasing their survival and dispersal ability

  • increased precipitation might benefit pathogens which rely on water for dispersal

• Range Shifts

  • plants and insects are well adapted to track changing climate and might infest new habitats as they move

  • insects and pathogens might gain new hosts as native and non-native plants move in response to climate change

• Additive effects

  • Mechanical damage caused by extreme weather events or herbivory can create opportunity for pathogens to infest otherwise healthy plants

• Examples from case studies

  • The distribution of the HWA is limited by cold tolerance and the outbreaks of the latter might be controlled by early growing season warmth and asynchrony between the insect and its host plants

  • Beech bark disease and Armillaria root rot both act as secondary infections to plants with damaged tissue. The primary damaging agent differs (weather damage vs. insect damage), reinforcing the need to understand the ecology of the species.

  • Invasive plants will respond to different factors including cold tolerance (e.g., Glossy buckthorn) and dispersal limitation (e.g., Oriental bittersweet)

Management implications

• Management for single species will be particularly difficult. Managers should consider a whole system approach to management.

• Quantitative measures of uncertainty and risk will be useful for management decisions. A framework for this can be found in Maguire, L.A. 2004. What can decision analysis do for invasive species management? Risk Anal. 24(4): 859–868. doi:10.1111/j. 0272-4332.2004.00484.x. PMID:15357805

Keywords

Shifting Seasons; Range Expansion; Review; Terrestrial Habitat; Risk Assessment