For the first time, scientists have used satellite images to demonstrate a link between rapid city growth and rainfall patterns, as well as to assess compliance with an international treaty to protect wetlands. The results have been published in two studies co-authored by Karen Seto, assistant professor of geological and environmental sciences and a fellow at the Woods Institute for the Environment at Stanford University.
''The exciting thing is really for the first time, using a time series of satellite images, we can monitor Earth in a way that we haven't been able to,'' Seto said. ''It's not just about urban growth or wetlands-it could be about desertification or deforestation-but it's really just this issue of human modification of the Earth.''
In one study, published in the July online issue of the journal Global Environmental Change, Seto and her colleagues showed that inclusion in an international environmental agreement did not significantly improve the health of a coastal mangrove habitat in a wetland preserve in Vietnam. In the second study, published May 15 in the Journal of Climate, the researchers found that rapid urban growth has caused drier winters in the Pearl River Delta of China.
Both findings are based on an analysis of satellite images of Vietnam and China, which NASA has been collecting through its Land Remote-Sensing Satellite (Landsat) Program for more than 30 years.
Urban growth in China
The Journal of Climate study focused on the People's Republic of China, where special economic zones have been established to attract foreign investment and generate international trade. One zone, Shenzhen, was created in 1980 in the Pearl River Delta just north of Hong Kong. Seto, a Hong Kong native, witnessed the impact of this designation during successive visits with relatives in mainland China.