COS 12-3 - Remotely sensed assessment of urbanization effects on local climate and vegetation in China

Monday, August 8, 2016: 2:10 PM
222/223, Ft Lauderdale Convention Center
Decheng Zhou, Nanjing University of Information Science &Technology, Liangxia Zhang, Nanjing University of Information Science and Technology, Nanjing, China and Ge Sun, Eastern Forest Environmental Threat Assessment Center, USDA Forest Service, Raleigh, NC

As the world’s most populous country, China has experienced the rapidest urbanization in past three decades worldwide and this trend is expected to continue in upcoming decades. The urban dwellers increased from 190 million in 1980 to 758 million in 2014 (accounting for 20 per cent of the global total at present) and this number is predicted to become 1.04 billion by 2050. There is no doubt that urban areas play an irreplaceable role in achieving a sustainable future for human societies, such as the centers of wealth creation, social services, culture, and politics. However, they have been causing many environmental issues which have already seriously affected human health and well-beings. Quantifying and analyzing urban-induced environmental changes in China is essential for formulating the sustainable development plans in the country. Using MODIS and Landsat data, we examined the urbanization effects on local climate and vegetation in 32 major Chinese cities. 


We indicated that there were evident urban heat island effects for those 32 major Chinese cities and the magnitudes varied greatly by time periods and geographic locations that depend strongly on local climate-vegetation regimes and other factors such as albedo, built-up intensity, and anthropogenic heat releases. Moreover, the UHI effects transcend far from urban physical boundary, with annual mean footprint of 2.3 and 3.9 times the actual urban size for the day and night, respectively. Urbanization can strongly affect local vegetation phenology that was closely related to UHI effects. On average across cities, the growing season started 12 days earlier and ended 5 days later in urban zones compared to rural areas for those 32 major cities. Further, we showed that urbanization reduced overall vegetation activity in most of the cities except two arid cities, but the actual urbanization effects were much weaker than the theoretical impacts because of the offsetting positive effects generated by multiple urban environmental and anthropogenic factors.