Heat Reduction Capabilities of Urban Tree Species

Cities are predicted to house 61% of the world’s population within the next 30 years and their ecological footprints extend much farther than the extent of developed land. In addition, they trap 15-30% more radiation than their rural counterparts, making air temperatures 0.6 - 1.3° C warmer. Higher temperatures drive chemical reactions and increases the energy expended in buildings for cooling. In this study, the thermal effects of tree species in Santa Barbara, California were observed using data from the Airborne Visible Infrared Imaging Spectrometer-Next Generation (AVIRIS-NG) satellite on June 3, 2014, and MASTER data from June 4, 2014. A spectral library was developed using image endmembers from reference polygons from Dar Roberts’ and Mike Alonzo’s datasets, and optimized the library using Iterative Endmember Selection (IES). With the spectral library, 33 most popular tree species in the city were mapped in addition to nonphotosynthetic vegetation (NPV), soil, and impervious surfaces. The image was unmixed using Multiple Endmember Spectral Mixture Analysis (MESMA) to analyze the pixels and a species map was constructed including the fractional cover. With this map we looked at the correlation of land surface temperature (LST) from the MASTER imagery to impervious surfaces and vegetation and found that impervious surfaces were correlated to higher LST and vegetation had the opposite effect, as well as four tree species that were most correlated to these lower temperatures.