Using spatiotemporal correlative niche models for evaluating the effects of climate change on mountain pine beetle

Includes bibliographical references.2015 Summer.Over the last decade western North America has experienced the largest mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreak in recorded history and Rocky Mountain forests have been severely impacted. Although bark beetles are indigenous to North American forests, climate change has facilitated the beetle’s expansion into previously unsuitable habitats. I used three correlative niche models (MaxEnt, Boosted Regression Trees, and Generalized Linear Models) to estimate: (i) the current potential distribution of the beetle in the U.S. Rocky Mountain region, (ii) how this extent has changed since historical outbreaks in the 1960s and 1970s, and (iii) how the potential distribution may be expected to change under future climate scenarios. Additionally, I evaluated the temporal transferability of the niche models by forecasting historical models and testing the model predictions using temporally independent outbreak data from the current outbreak. My results indicated that there has been a significant expansion of climatically suitable habitat over the past 50 years and that much of this expansion corresponds with an upward shift in elevation across the study area. Furthermore, my models indicate that drought was a more prominent driver of current outbreak than temperature, which suggests a change in the climatic signature between historical and current outbreaks. The current climatic niche of the mountain pine beetle includes increased precipitation, colder winter temperatures, and a later spring than the historical climatic niche, which reflects a shift into higher elevation habitats. Projections under future conditions suggest that there will be a large reduction in climatically suitable habitat for the beetle and that high-elevation forests will continue to become more susceptible to outbreak. While all three models generated reasonable predictions (AUC = 0.85 - 0.87), the generalized linear model correctly predicted a higher percentage of current outbreak localities when trained on historical data. My findings suggest that projects aiming to reduce omission error in estimates of future species responses may have greater predictive success with simpler, generalized models

Historical and event-based bioclimatic suitability predicts regional forest vulnerability to compound effects of severe drought and bark beetle infestation

Vulnerability to climate change, and particularly to climate extreme events, is expected to vary across species ranges. Thus, we need tools to standardize the variability in regional climatic legacy and extreme climate across populations and species. Extreme climate events (e.g., droughts) can erode populations close to the limits of species' climatic tolerance. Populations in climatic-core locations may also become vulnerable because they have developed a greater demand for resources (i.e., water) that cannot be enough satisfied during the periods of scarcity. These mechanisms can become exacerbated in tree populations when combined with antagonistic biotic interactions, such as insect infestation. We used climatic suitability indices derived from Species Distribution Models (SDMs) to standardize the climatic conditions experienced across Pinus edulis populations in southwestern North America, during a historical period (1972-2000) and during an extreme event (2001-2007), when the compound effect of hot drought and bark beetle infestation caused widespread die-off and mortality. Pinus edulis climatic suitability diminished dramatically during the die-off period, with remarkable variation between years. P. edulis die-off occurred mainly not just in sites that experienced lower climatic suitability during the drought but also where climatic suitability was higher during the historical period. The combined effect of historically high climatic suitability and a marked decrease in the climatic suitability during the drought best explained the range-wide mortality. Lagged effects of climatic suitability loss in previous years and co-occurrence of Juniperus monosperma also explained P. edulis die-off in particular years. Overall, the study shows that past climatic legacy, likely determining acclimation, together with competitive interactions plays a major role in responses to extreme drought. It also provides a new approach to standardize the magnitude of climatic variability across populations using SDMs, improving our capacity to predict population's or species' vulnerability to climatic change

A recreation ecology perspective on the COVID-19 (SARS-CoV-2) pandemic: Potential parks and protected area impacts relating to visitor spatial use, terrestrial flora and fauna, and management

Measures to limit the spread of COVID-19 require changes in the ways that people travel, gather, and recreate in outdoor spaces. In 2020, to limit human-to-human transmission of COVID-19, US park and protected area managers at all levels of governance implemented closures and restrictions on the types of activities and facilities available for public use. At the same time, the US Centers for Disease Control and Prevention outlined suggestions for social distancing, wearing face masks, and limiting travel and group sizes for social gatherings. This thought piece explores potential shifts in park accessibility and human behaviors that may lead to cascading impacts on visitor spatial use, terrestrial flora and fauna, and park management. We discuss potential changes in visitor spatial behavior and possible subsequent ecological impacts on terrestrial flora and fauna. Additionally, we connect these topics with management implications and emphasize adaptive management and continued monitoring to address current and future pandemic-related issues. We provide park managers, researchers, and other professionals with expected social and ecological implications resulting from managerial and behavioral shifts in response to the COVID-19 pandemic. Furthermore, we suggest management approaches to address and monitor these impacts. This information can help shape how park managers respond to the ongoing pandemic and future human health issues that impact park visitors and flora and fauna. Finally, we offer suggestions for where prospective researchers can direct their focus, especially in areas where recreation ecology and human disease management intersect