Assessing the impacts of global warming on forest pest dynamics

Abstract

Forest insects and pathogens are the most pervasive and important agents of disturbance in North American forests, affecting an area almost 50 times larger than fire and with an economic impact nearly five times as great. The same attributes that result in an insect herbivore being termed a "pest" predispose it to disruption by climate change, particularly global warming. Although many pest species have co-evolved relationships with forest hosts that may or may not be harmful over the long term, the effects on these relationships may have disastrous consequences. We consider both the data and models necessary to evaluate the impacts of climate change, as well as the assessments that have been made to date. The results indicate that all aspects of insect outbreak behavior will intensify as the climate warms. This reinforces the need for more detailed monitoring and evaluations as climatic events unfold. Luckily, we are well placed to make rapid progress, using software tools, databases, and the models that are already available.

Regional vegetation die-off in response to global-change-type drought

“…The warmer temperatures associated with the recent drought would have increased the energy load and water stress demands on the trees and may account for the apparently greater resulting mortality. The effects of water and temperature stress during the recent drought could have been further exacerbated by (i) anomalously high precipitation in the southwestern North America from about 1978-1995 that allowed rapid tree growth and increased stand densities, resulting in potentially greater intraspecific competition for drought-limited water and greater susceptibility to drought, beetle infestation, and associated pathogens (22) and͞or (ii) amplifying effects of warmer temperatures and longer growing seasons on beetle growth rates and population dynamics (23). Nonetheless, previous studies of drought-induced die-off have highlighted the underlying importance of water stress in triggering die-off (5,20).…”

Temperature-driven range expansion of an irruptive insect heightened by weakly coevolved plant defenses

“…These effects are likely to be particularly strong for species interactions, especially those involving ectotherms (2), which comprise the most abundant and diverse animal taxa on the biosphere. For example, there are already well-documented examples of insects colonizing elevations and latitudes beyond their historic limits in response to recent warming trends (1,2). The resulting new host-plant associations have uncertain longterm consequences, but could potentially alter fundamental ecosystem processes and lead to new dynamics of relationships among species on the landscape.…”

Forest Economics, Natural Disturbances and the New Ecology

“…Finally, we note that climate change might alter slow-fast ecosystem dynamics for some important forest disturbances (Dale et al 2000, Logan et al 2003. Westerling et al (2006) identified a statistically significant change in the annual frequency of large (> 400 ha) western United States wildfires after 1987 that was correlated with mean March through August temperatures, suggesting that climatic thresholds may be important for fire dynamics.…”