Challenges for Applied Remote Sensing Science in the Urban Environment

Land cover and land use changes associated with urbanization are important drivers of local geological, hydrological, ecological, and climatic change. Quantification and monitoring of these changes in 100 global urban centres are part of the mission of the ASTER instrument on board the NASA Terra satellite, and comprise the fundamental research objective of the Urban Environmental Monitoring (UEM) Program at Arizona State University. Data have been acquired for the majority of the target urban centres and are used to compare landscape fragmentation patterns on the basis of land cover classifications at both local and global scales. Despite the promising and exciting possibilities presented by new and fast-developing sensors and technologies we still perceive a gap between the generally academic and research-focused spectrum of results offered by the “urban remote sensing’ community and the application of these data and products by the local governmental bodies of urban cities and regions. In a recently organized workshop with partners from six urban regions all over the world we tried to determine what the important questions are, and how we can use our data and scientific skills to help answer them. 1. CURRENT RESEARCH OBJECTIVES Arizona State University (ASU, the host of the Urban Remote Sensing conferences 2005) through its Urban Environmental Monitoring project (UEM, http://elwood.la.asu.edu/grsl/UEM/) is particularly qualified to provide remote sensing technology and expertise in promoting urban sustainability around the world. The Department of Geological Sciences’ Geological Remote Sensing Laboratory, in conjunction with the Center for Environmental Studies, has initiated research on 100 cities around the world using data from NASA’s Earth Observing System (EOS) as well as other satelliteand airborne-based datasets (Stefanov and Netzband, in press). These high spatial and spectral resolution image data can provide key information that allows decision makers to monitor: urban densities; urban geo-hazards; new developments on the urban fringe; the spread of impermeable surfaces, soil erosion and dust formation; the transformation of agricultural lands; changes in local microclimates, surface water flow and reservoir capacity; primary productivity of local vegetation; condition of transportation arteries; and key aspects of air pollution. Over the past two years, ASU scientists from a variety of disciplines including geology, engineering, geography, ecology, and sociology have been developing a comprehensive series of metrics to characterize the spatial and socio-ecological structure of cities together with methods to validate the inferred patterns. Much of this current work focuses upon Phoenix, taking advantage of the extensive on-the-ground resources of the Central Arizona–Phoenix Long Term Ecological Research (CAP LTER) project. To further test these methods, we are now forming an expanding network of partner cities in the developed world where scientific resources are readily available, and in developing countries where there is great enthusiasm for applying this approach to pressing environmental problems. In parallel with the growth of this network, we are collaborating with government agencies (such as NASA) and the scientific community to establish an enhanced satellite system that directly serves the needs of urban areas. While characterization and monitoring of ongoing urbanization processes is important, equally important is the ability to predict the local and regional environmental effects and feedbacks associated with expanding urban centres (Grimm et al., 2000). We define six major research objectives to achieve this goal: Objective 1: Tracking urban area growth and change: speed, density, direction, structures, impervious surfaces, land use consumed. Objective 2: Spatial arrangement of green/open space within cities and at periphery: amount distribution, links. Objective 3: Track changes in peri-urban regions: farmland conversions, wetland infringement, biodiversity threats. Objective 4: Monitor land cover/land use changes that influence urban climatology and atmospheric deposition. Objective 5: Monitor urban growth as it intersects areas of potential environmental hazards: earthquake, subsidence, mudslides, floods, etc. Objective 6: Map environmental parameters such as microclimate, heat island, access to open space, percent impervious surface, percent green space and assess the geographic differences within regions and whether they correlate with social, economic, or ethnic divisions. The UEM project is using a variety of remotely sensed and GIS datasets (ASTER, Landsat, MODIS, astronaut photography, socioeconomic data, historical maps) to establish development trajectories within a pilot study for 8 urban centers located around the globe. Figure 1. Location map of eight "intensive study" cities. Red squares indicate other UEM cities. These urban centers (Berlin, Germany; Cairo, Egypt; Chiang Mai, Thailand; Delhi, India; Mexico City, Mexico; Lima, Peru; and Phoenix, Arizona, USA) are selected on the basis of urban growth projections, geologic/geographic setting, and climatic patterns. Our initial goal is to determine classes or groupings of urban development trajectories defined by several variables (land use/land cover, landscape metrics, climatic patterns, geologic hazard assessment, and development history). The understanding of how these urban centers have developed and responded to various environmental, climatic, and sociopolitical stressors will inform models of how sustainable they are given similar future stressors (Alberti and Waddell, 2000). Improvement in understanding of urban resilience and sustainability is of great importance to scientists, policy-makers, and citizens alike. The models we develop will allow policymakers to incorporate remotely sensed data into their local and regional planning efforts. Within the UEM project we will continue to produce standardized land cover classifications for 100 urban centers located around the globe using ASTER data throughout the duration of the Terra mission. In addition, we will monitor the geological and ecological status of these cities using ASTER and MODIS. Classification of urban development trajectories and spatial structure will be determined for a representative subset of 8 urban centers (see figure 1) using a coherent methodological approach to ensure comparability of the results. Ongoing research in this area includes development of detailed land cover classification models for the eight study cities (figure 2). Figure 2. Land cover classification for the eastern Phoenix area. 2. KEY PROBLEMS THAT NEED TO BE ADDRESSED BY URBAN REMOTE SENSING At Arizona State University (ASU) a brainstorming meeting took place on February 18, 2004 in order to assess and evaluate the potentials and demands on Remote Sensing in Urban Areas. The following topical questions were considered as a framework: 1. What are the key social and physical questions that should be addressed using urban remote sensing technology and data? a. In general, what challenges to sustainability are faced by urban regions? b. b. Which of these challenges do you see in the urban regions with which you are familiar? c. What (if any) solutions are applied to these challenges? d. How can the outcome of these solutions be enhanced with the application of remote sensing? 2. What are the regional and global impacts of the social problems associated with urban regions?