Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Satellite images reveal link between urban growth and changing rainfall patterns

04.07.2007
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.

In a previous paper, Seto and her colleagues analyzed satellite imagery and found that urban areas in the Pearl River Delta increased more than 300 percent from 1988 to 1996. In the Journal of Climate study, the researchers compared this rapid urban growth with monthly temperature and precipitation data from 16 meteorological stations. Their analysis revealed a direct correlation between the rapid growth of cities and a decrease in rainfall during the winter dry seasons from 1988 to 1996.

''We found that as the cities get bigger, there is a negative impact on precipitation patterns, such that in the winter season there is a reduction in rainfall as an effect of urbanization,'' Seto explained. ''Primarily it is caused by the conversion of vegetated land to asphalt, roads and buildings. As a result, the soils have significantly less ability to absorb water, so in the winter months there is less moisture in the atmosphere and therefore a reduction in precipitation. We don't see the same impact in summer months, in part because the effect of the Asian monsoon masks the effect of urbanization.''

''When cities are still relatively small, we don't see this pattern emerging,'' she added. ''It happens when cities get very large. But that's the part that I think is alarming, because we see large-scale city development all over China and throughout the developing world.''

Coastal changes in Vietnam

In the Global Environmental Change study, the researchers focused on Vietnam, a signatory of the Convention on Wetlands of International Importance Especially as Waterfowl Habitat, drafted in Ramsar, Iran, in 1971. The goal of the treaty was to protect wetlands by promoting sustainable use of resources found there. To date, more than 150 countries, including the United States, have signed the convention. The Florida Everglades and portions of the Ganges River in India and the Red River Delta in northern Vietnam are included on the convention's list of wetlands of international importance.

The growth of aquaculture in recent years has threatened coastal mangrove forest habitats in the Red River Delta. In response, the Vietnamese government has established protected areas, such as the Xuan Thuy Natural Wetland Reserve, which was designated a Ramsar site in 1988.

For the study, Seto and her colleagues concentrated on Xuan Thuy and a nearby reserve that is not included in the Ramsar treaty. The researchers analyzed a series of Landsat images taken between 1975 and 2002. Analysis revealed that both reserves experienced increased fragmentation of mangrove forest habitat with increased aquaculture. Contrary to expectations, the scientists found that aquaculture developed at a faster rate at the Xuan Thuy treaty site than at its non-Ramsar neighbor.

These findings mirrored statements by local residents in 2001, when Seto and her co-workers interviewed one-third of the households living and farming within the boundaries of both reserves. The researchers were told that aquaculture had been ongoing in the region since the early 1980s.

These results showed that satellite technology is a cost-effective means of assessing wetland health, Seto said, noting that the cost of acquiring the satellite images and conducting the interviews in the field totaled less than $5,000.

This technique could be used to verify compliance with other environmental agreements, added Ron Mitchell, professor of public policy at the University of Oregon and an expert on multi-national environmental treaties. ''Too often in the past policymakers have been at a loss as to how to evaluate progress,'' he said. ''Remote sensing could be used to evaluate many international environmental agreements, particularly habitat-based conventions, such as Ramsar or those dealing with deforestation, desertification and carbon sequestration projects under a climate change agreement.''

Mark Shwartz | EurekAlert!
Further information:
http://www.ramsar.org/
http://environment.stanford.edu/
http://landsat.gsfc.nasa.gov/

More articles from Earth Sciences:

nachricht A promising target in the quest for a 1-million-year-old Antarctic ice core
24.05.2018 | University of Washington

nachricht Tropical Peat Swamps: Restoration of Endangered Carbon Reservoirs
24.05.2018 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>