Carbon Sequestration and Urban Heat Island Mitigation by Urban Forests

Abstract

Nature-based carbon sequestration is one of the most straightforward ways to extract and to store carbon dioxide from the atmosphere. Urban forests hold the promise of optimized carbon storage and temperature reduction in cities. Remote sensing imagery can identify tree location and size, classify trees based on their species, and track tree health. Using multi- and hyperspectral overhead imagery, green vegetation can be separated from various land use types. Moreover, through further refinement of models by texture and contextual information, trees can get spatially separated from bushes and grass covered surfaces. While spectral-based tree identification can achieve accuracy of 90%, additional deep learning models using even noisy labeled data can further improve tree identification models. Once trees are identified in two-dimensional remote sensing images, allometric models allow to extract tree height and tree growth based on climate data, topography, and soil properties. The biomass of the trees is calculated for tree species using geometrical and phenological models. The carbon stored in trees can be quantified at individual tree level. Furthermore, the models allow to identify areas densely covered by trees to pinpoint bare land where further trees may be planted. Exploiting land surface temperature maps from satellite thermal measurements of, e.g., the Sentinel or Landsat missions, urban heat island can be mapped out at city scale. Urban heat islands may vary based on season and weather conditions; areas persistently warmer when compared to average city temperature background can be identified from time series of data. The correlation of local temperature, tree cover, and land perviousness helps to identify local climate zones. It also may refine and re-evaluate the definition of Local Climate Zones (LCZ). We employ the PAIRS geospatial information platform to demonstrate a scalable solution for tree delineation, carbon sequestration, and urban heat island identification for three global cities: Madrid, New York City, and Dallas, TX.