A mountain pine beetle (Dendroctonus ponderosae Hopkins) epidemic has caused widespread mortality of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) trees across western North America,. We characterized the initial effects of beetle-induced mortality on forest structure and composition in Rocky Mountain National Park, Colorado. In 2008, we surveyed stand structure and tree species composition across lodgepole pine dominated forests in the western portion of the Park. We defined five lodgepole pine forest types to describe variability in pre-epidemic forest conditions. This forested landscape appears to be resilient to the effects of the beetle. Surviving trees, including both canopy trees and saplings, were plentiful in most of the post-epidemic forests, even after accounting for anticipated future mortality. Subalpine fir (Abies lasiocarpa (Hook.) Nutt.), Engelmann spruce (Picea engelmannii Parry ex Engelm.), and aspen (Populus tremuloides Michx.) had modestly higher relative abundances after the epidemic. Lodgepole pine remained the dominant species on approximately 85% of the landscape. The impact of the outbreak on forest structure and composition varied considerably among the five forest types, suggesting that post-epidemic forest developmental trajectories will vary according to preoutbreak stand characteristics. Active management efforts to regenerate lodgepole pine forests, e.g., tree planting, will likely not be necessary on this landscape.Résumé : Une épidémie de dendroctone du pin ponderosa (Dendroctonus ponderosae Hopkins) a causé beaucoup de mortalité chez le pin tordu latifolié (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) partout dans l'ouest de l'Amérique du nord. Nous avons caractérisé les premiers effets de la mortalité causée par le dendroctone sur la structure et la composition de la forêt dans le parc national des Montagnes Rocheuses, Colorado. En 2008, nous avons inventorié la structure et la composition en espèces d'arbres des peuplements parmi les forêts dominées par le pin tordu dans la partie ouest du parc. Nous avons défini cinq types de forêts de pin tordu pour décrire la variabilité de la forêt qui existait avant l'épidémie. Ce paysage forestier semble résilient aux effets du dendroctone. Les arbres qui ont survécu, incluant des arbres dominants et des gaules, étaient nombreux dans la plupart des forêts après l'épidémie, même en tenant compte de la mortalité anticipée. Le sapin subalpin (Abies lasiocarpa (Hook.) Nutt.), l'épinette d'Engelmann (Picea engelmannii Parry ex Engelm.) et le peuplier faux-tremble (Populus tremuloides Michx.) avaient une abondance relative légèrement plus élevée après l'épidémie. Le pin tordu demeurait l'espèce dominante dans environ 85 % du paysage. L'impact de l'épidémie sur la composition et la structure de la forêt variait considérablement parmi les cinq types forestiers, ce qui indique que la trajectoire du développement de la forêt après une épidémie variera en fonction des caractéristiques du peuplement avant une épidém...

Redlining was a racially discriminatory housing policy established by the federal government’s Home Owners’ Loan Corporation (HOLC) during the 1930s. For decades, redlining limited access to homeownership and wealth creation among racial minorities, contributing to a host of adverse social outcomes, including high unemployment, poverty, and residential vacancy, that persist today. While the multigenerational socioeconomic impacts of redlining are increasingly understood, the impacts on urban environments and ecosystems remain unclear. To begin to address this gap, we investigated how the HOLC policy administered 80 years ago may relate to present-day tree canopy at the neighborhood level. Urban trees provide many ecosystem services, mitigate the urban heat island effect, and may improve quality of life in cities. In our prior research in Baltimore, MD, we discovered that redlining policy influenced the location and allocation of trees and parks. Our analysis of 37 metropolitan areas here shows that areas formerly graded D, which were mostly inhabited by racial and ethnic minorities, have on average ~23% tree canopy cover today. Areas formerly graded A, characterized by U.S.-born white populations living in newer housing stock, had nearly twice as much tree canopy (~43%). Results are consistent across small and large metropolitan regions. The ranking system used by Home Owners’ Loan Corporation to assess loan risk in the 1930s parallels the rank order of average percent tree canopy cover today.

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Warmer temperatures are expected to increase the incidence of Lyme disease through enhanced tick maturation rates and a longer season of transmission. In addition, there could be an increased risk of disease export because of infected mobile hosts, usually birds. A temperature-driven seasonal model of Borrelia burgdorferi (Lyme disease) transmission among four host types is constructed as a system of nonlinear ordinary differential equations. The model is developed and parametrized based on a collection of lab and field studies. The model is shown to produce biologically reasonable results for both the tick vector (Ixodes scapularis) and the hosts when compared to a different set of studies. The model is used to predict the response of Lyme disease risk to a mean annual temperature increase, based on current temperature cycles in Hanover, NH. Many of the risk measures suggested by the literature are shown to change with increased mean annual temperature. The most straightforward measure of disease risk is the abundance of infected questing ticks, averaged over a year. Compared to this measure, which is difficult and resource-intensive to track in the field, all other risk measures considered underestimate the rise of risk with rise in mean annual temperature. The measure coming closest was “degree days above zero.” Disease prevalence in ticks and hosts showed less increase with rising temperature. Single field measurements at the height of transmission season did not show much change at all with rising temperature.