Southern and Mexican pine beetles and climate change: An assessment of potential ecological and economic effects of a range shift

Background/Question/Methods

Predicted climate warming is likely to have profound effects on bark beetle population dynamics in the southwestern United States. Temperature-mediated effects may include increases in developmental rates and generations per year. As a result, the impacts of southern (Dendroctonus frontalis) and Mexican (D. mexicanus) pine beetles on forest resources are subject to foreseeable amplification. To assess the implications of such change, we evaluated the generations per year of these species under three climate scenarios using a degree-day model of development. 

Results/Conclusions

Across the southwestern U.S.A. and northern Mexico, the potential number of generations per year increased from 1-3+ under historical climate to 2-4+ under the minimal warming scenario and 3-5+ under the greatest warming scenario.  Using habitat based models, Maxent and Daymet, we also determined potential habitat for these species across the western U.S.A.  For the southwestern U.S.A., we assessed economic impacts of increased beetle outbreaks in terms of the costs of application of preventative silvicultural treatments and potential economic revenues forgone.  Economic benefits of applying basal area reduction treatments to reduce forest susceptibility to beetle outbreaks ranges from $168.31/ha (NM) to $261.13/ha (AZ) under historical conditions, and $2,359.52/ha (NM) to $2,686.33/ha (AZ) under simulated severe drought conditions. Coupled with other deleterious consequences associated with beetle outbreaks, such as increased wildfires, the results suggest that forest thinning treatments play a useful role in a period of climate warming.  Implications of this modeling effort include a better understanding of the role of climatic change, which may result in native species becoming invasive or moving across political boundaries into new ranges.  Our study benefited from the inclusion of an economist to guide our economic analysis; the integration between ecology and economics should be utilized more frequently in invasive species research and management.  In this case, proactive management was shown to be more economically sound than no action.