Scientific Publications

Scientists from Dr. Darrel Jenerette’s team have published several scientific articles related to the goals of the Earthwatch Urban Resiliency Program. Summaries of select articles show the contributions of citizen science to research.


Tayyebi A and GD Jenerette. 2016. Increases in the climate change adaption effectiveness and availability of vegetation across a coastal to desert climate gradient in metropolitan Los Angeles, CA, USA. Science of the Total Environment 548-549:60-71

 

The Los Angeles, CA metropolitan region has a pronounced coastal to desert climate gradient from cooler and moister coast to a drier and hotter inland region. In this study, Drs Tayyebi and Jenerette sought to identify how changes in vegetation (measured by normalized difference vegetation index) were related to land surface temperatures (LST) across different socioeconomic neighborhoods (assessed by income). To do this, they used information from NASA overflights taken in May 2013 to assess the vegetation based surface cooling services and land surface temperature. They found that cooling effectiveness of vegetation increased with distance from the coast. Whereas vegetation decreased urban heat by 16 degrees F along the coast, it help cool by 67 degrees F is the desert areas roughly 16 miles from the coast. They also found that higher income neighborhoods were greener and cooler, and that this cooling effect most prominent at about 30 km from the coast.

These results show the availability and effectiveness of vegetation on the local climate varies tremendously throughout the Los Angeles, CA metropolitan area. Further, using the more inland climate zones as future analogs for more coastal zones, suggests that for future climate conditions, the effectiveness and value of vegetation to help cooling is likely to increase.


Avolio ML, DE Pataki, TW Gillespie, Jenerette GD, HR McCarthy, S Pincetl, and LW Clarke. 2015. Tree diversity in southern California’s urban forest: the interacting roles of social and environmental variables. Frontiers in Ecology and Evolution

 

Understanding whether there is a match between what people prefer in their local environment and what is found there can reveal much about the driving factors that ultimately determine the kinds of green space we live in. This is especially true in places such as Southern California, which is rich in an imported tree diversity reflecting the diversity of people found. Avolio et al. examined which trees were found in neighborhoods across Los Angeles, Orange and Riverside counties to better understand the extent to which people’ preferences are related to the diversity of trees found there. Are the trees found in yards, streets and parks reflective of people’s stated preferences? To do this, researchers selected a range of neighborhoods across each county and randomly surveyed trees in smaller plots.  They analyzed both which trees were found where, and also the preferences of the people there for trees based on the ecosystem services trees could provide such as shade, attractiveness, edible fruit, or water needs.

The scientists found that the tree species found in a location was often a function of people’s choices, but not always so – especially in lower income neighborhoods. People living in hotter neighborhoods preferred trees that were shady, which was reflected by evidence that trees providing better shade were found there in greater proportion than in cooler neighborhoods. Similar matches between people’s preferences and trees planted was found when comparing trees residential areas which had more fruiting trees and street trees which had lower water needs and required less maintenance. Residential neighborhoods may plant trees more for “provisioning” ecosystem services while city managers are more concerned with tree water requirements and maintenance.

However, some mismatches were also found. While residents in more arid areas had a greater preference for trees that required less water, they did not find that drier neighborhoods had more drought tolerant trees. Moreover, preferences for fruit trees was more important to low income than high-income residents, but the proportion of fruit trees in neighborhoods was not related to income. A possible cause of these mismatches between preferences and trees found in the urban forest is that economic factors can limit or enable mismatches. Monetary limitations may restrict the ability of lower income residents to create tree communities that match their preferences, and subsidized water may not restrict planting of drought intolerant trees. The results of this research suggest that people do pay attention to the ecosystem “traits” that different trees possess, such as shadiness or drought tolerance, and that framing management and public awareness around the ecosystem traits that trees possess is a useful approach in creating a more resilient Southern California.


Jenerette GD, SL Harlan, A Buyantuev, WL Stefanov, J Declet-Barreto, BL Ruddell, S Myint, S Kaplan, and X Li. 2016. Micro scale urban surface temperatures are related to land cover features and heat related health impacts in Phoenix, AZ USA. Landscape Ecology 31:745-760

 

The projected increase by 2.5 billion more urban residents globally by the year 2050 could lead to significant human health risks due to extreme heat often associated with highly urbanized areas. Moreover, the problems of heat stress will only get more acute with climate change. In this study, scientists Jenerette et al. investigated variations in land surface temperature, land cover, and residents’ perceptions of landscapes and heat illnesses in the city of Phoenix, AZ USA.  They used images from remote sensing technology to gather high resolution urban land surface temperature data during the day and night.  They also used information from household surveys to understand people’s health effects and their perception of heat. For the first time, scientists linked these two data sets – high resolution land surface temperature and resident experiences at the individual parcel level. They then analyzed the data throughout a whole day, rather than only at one time of the day, and at scales that humans live at, such as their homes and yards.  The study found that even at small-scales, the kind of land use (i.e. vegetation, pavement, etc.) was related to surface temperatures and the effects differed between day and night. Furthermore, vegetation was most effective at cooling hotter neighborhoods.  In addition, residents’ perceptions of heat risk and symptoms of heat-related illness were correlated with high daytime temperatures, but no corresponding relationship was observed with nighttime temperatures.  Overall, by using new methods, this study presents results that suggest that even at the very local scale of households, managing one’s vegetation can help reduce the heat exposure risk of urban residents. Importantly, vegetation will be of greatest help where heat stress is likely to be greatest.  These findings take us a step closer towards building heat resilient cities.


Other publications

Avolio ML, DE Pataki, S Pincetl, T Gillespie, GD Jenerette, and HR McCarthy. 2015. Understanding preferences for tree attributes: the relative effects of socio-economic and local environmental factors. Urban Ecosystems 18:73-86

Clarke LW and GD Jenerette. 2015. Biodiversity and direct ecosystem service regulation in the community gardens of Los Angeles, CA. Landscape Ecology 30:367-653

Clarke LW, GD Jenerette, and A Davalia. 2013. The luxury of vegetation and the legacy of tree biodiversity in Los Angeles, CA. Landscape and Urban Planning 116:48-59
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