Jason Vargo

Avoided Heat-Related Mortality through Climate Adaptation Strategies in Three US Cities

Heat-related mortality in US cities is expected to more than double by the mid-to-late 21st century. Rising heat exposure in cities is projected to result from: 1) climate forcings from changing global atmospheric composition; and 2) local land surface characteristics responsible for the urban heat island effect. The extent to which heat management strategies designed to lessen the urban heat island effect could offset future heat-related mortality remains unexplored in the literature. Using coupled global and regional climate models with a human health effects model, we estimate changes in the number of heat-related deaths in 2050 resulting from modifications to vegetative cover and surface albedo across three climatically and demographically diverse US metropolitan areas: Atlanta, Georgia, Philadelphia, Pennsylvania, and Phoenix, Arizona. Employing separate health impact functions for average warm season and heat wave conditions in 2050, we find combinations of vegetation and albedo enhancement to offset projected increases in heat-related mortality by 40 to 99% across the three metropolitan regions. These results demonstrate the potential for extensive land surface changes in cities to provide adaptive benefits to urban populations at risk for rising heat exposure with climate change.

The importance of land cover change across urban–rural typologies for climate modeling

Land cover changes affect local surface energy balances by changing the amount of solar energy reflected, the magnitude and duration over which absorbed energy is released as heat, and the amount of energy that is diverted to non-heating fluxes through evaporation. However, such local influences often are only crudely included in climate modeling exercises, if at all. A better understanding of local land conversion dynamics can serve to inform inputs for climate models and increase the role for land use planning in climate management policy. Here we present a new approach for projecting and incorporating metropolitan land cover change into mesoscale climate and other environmental assessment models. Our results demonstrate the relative contributions of different land development patterns to land cover change and conversion and suggest that regional growth management strategies serving to increase settlement densities over time can have a significant influence on the rate of deforestation per unit of population growth. Employing the approach presented herein, the impacts of land conversion on climate change and on parallel environmental systems and services, such as ground water recharge, habitat provision, and food production, may all be investigated more closely and managed through land use planning.

Climate change adaptation through urban heat management in Atlanta, Georgia.

This study explores the potential effectiveness of metropolitan land cover change as a climate change adaptation strategy for managing rising temperatures in a large and rapidly warming metropolitan region of the United States. Through the integration of a mesoscale meteorological model with estimated land cover data for the Atlanta, Georgia region in 2010, this study quantifies the influence of extensive land cover change at the periphery of a large metropolitan region on temperature within the city center. The first study to directly model a metropolitan scale heat transfer mechanism, we find both enhanced tree canopy and impervious cover in the suburban zones of the Atlanta region to produce statistically significant cooling and warming effects in the urban core. Based on these findings, we conclude that urban heat island management both within and beyond the central developed core of large cities may provide an effective climate change adaptation strategy for large metropolitan regions.

Metro sapiens: an urban species

A major step in our evolution occurred when we first began to organize and settle in cities. With more than half of the world’s population living in cities and all urban development since those first settlements expected to double by 2060 (UN 2011), cities are now very much the dominant habitat for our species. We are faced with a challenge to resolve our domesticated tendencies with resource and space limits of our planet. A fundamental aim of sustainability is to preserve the existence of our species; it is clear that we will need to embrace urbanism as a human quality to achieve that end. Our commitment to a global urban future demands that we move toward more sustainable urbanism. Accomplishing such a goal requires several important steps, all of which expand the fields of environmental and sustainability science and reinforce the value of considering urbanism. First, our relationship to urbanism should be expected to continue. Second, studies of cities and natural systems must recognize their inherent interdependencies. Finally, the local differences that make some cities healthier and ecologically supportive must be better understood. Each of these steps can generate broad research themes for new discovery. Recognizing our urban nature is a prerequisite.

Comparison of US metropolitan region pedestrian and bicyclist fatality rates

Annual US pedestrian and bicyclist fatalities involving motor vehicles have each increased by 30% in just six years, reaching their highest levels in two decades. To provide information to reverse this trend, we quantified pedestrian and bicyclist fatality rates in 46 of the largest US metropolitan statistical areas (MSAs) during two five-year time periods: 1999-2003 and 2007-2011. We divided the annual average number of pedestrian and bicyclist fatalities during 1999-2003 from the Fatality Analysis Reporting System by the annual estimates of pedestrian and bicycle trips, kilometers traveled, and minutes traveled from the 2001 National Household Travel Survey (NHTS) and the annual average number of fatalities from 2007 to 2011 by similar estimates from the 2009 NHTS. The five most dangerous regions for walking during 2007-2011 averaged 262 pedestrian fatalities per billion trips while the five safest averaged 49 pedestrian fatalities per billion trips. The five most dangerous regions for bicycling averaged 458 bicyclist fatalities per billion trips while the five safest averaged 75 bicyclist fatalities per billion trips. Random-effects meta-analysis identified eight metropolitan regions as outliers with low pedestrian fatality rates, six with high pedestrian fatality rates, one with a low bicyclist fatality rate, and five with high bicyclist fatality rates. MSAs with low pedestrian and bicycle fatality rates tended to have central cities recognized as Walk Friendly Communities and Bicycle Friendly Communities for investing in pedestrian and bicycle projects and programs. Random-effects meta-regression showed that certain socioeconomic characteristics and high pedestrian and bicyclist mode shares were associated with lower MSA fatality rates. Results suggest that pedestrian and bicycle infrastructure and safety programs should be complemented with strategies to increase walking and bicycling. In particular, safety initiatives should be honed to reduce pedestrian and bicyclist fatality risk in immigrant communities and to make pedestrian travel safer for the growing senior-age population.