Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Spring through fall, cities are greener longer than neighboring rural regions

29.07.2004


BU team shows so-called urban heat island effect influences onset of ’greenup,’ dormancy



Summer can sometimes be a miserably hot time for city dwellers, but new research shows that an urban setting allows plants to bask in a hot-house environment that keeps them greener longer.

Recent NASA-sponsored research from a team of geographers in Boston University’s Center for Remote Sensing shows that the growing season for vegetation in about 70 urban areas in North America is, on average, 15 days longer than that in rural regions surrounding the cities studied. Led by Xiaoyang Zhang, a research assistant professor in BU’s Geography Department, the team found that, like many urban-dwelling humans, urban greenery lives at a more intense pace, getting as much as a seven-day jump-start on spring and up to eight additional days before winter dormancy than vegetation in surrounding rural areas.


This happens largely because the asphalt, steel, exhaust, and other environmental changes introduced by humans contribute to what is known as the urban heat island effect. The researchers found this influence to be far-reaching. Taken together, the heat island effect for the areas studied ripples beyond urban boundaries to create an ecological "footprint" 2.4 times greater than that of urban land use in eastern North America.

Their analyses also show that changes in land surface temperatures and when vegetation first becomes green are not significantly related to urban size, leading the team to speculate that factors related to population density may play the more important role in the observed effects. The data do, however, show that "greenup" changes in surrounding rural areas are linked to city size -- the larger the city, the longer the reach of the extended greenup effect.

To date, more than one-third of the land surface of Earth has been transformed by human activities. These changes have not only altered the look of the land, but, according to a growing body of research, have also affected climate and significantly changed Earth’s ecosystems. In an attempt to determine the effect that the urban heat island phenomenon has on the growing season for urban vegetation, the BU team used satellite data to evaluate when vegetation in urban and rural settings first became green and then when it entered dormancy, thereby ending one season’s growing cycle.

The researchers calculated the onsets of vegetation greenup and dormancy for about 70 urban areas using so-called NBAR data gathered between January 1 and December 31, 2001, by NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS). The MODIS instrument, aboard NASA satellites Terra and Aqua, gathers data on Earth’s entire surface every one to two days. The team used "nighttime lights" data and MODIS data to determine the size of the urban areas studied.

To determine the radiating effect of urban heat islands on vegetation in surrounding regions, the researchers assessed greenup data in six, two-to-three kilometer zones demarcated from urban edges. Within these zones, to a total distance of 20 km., the scientists measured land-surface temperatures and vegetation greenup responses.

They found that greenup occurs earliest in urban areas but that urban climate shows a substantial influence on vegetation growing up to 10 km. beyond the edge of urban land cover. This greenup difference is especially pronounced in the Washington, DC–Philadelphia–New York City corridor, where urban greenup occurs about 5.5 days and 8.7 days earlier than in zones 0 – 3 km. and 8 – 10 km., respectively, from the urban edge. In all, they found the strength of the urban influence decreases with distance from the perimeter of urban land cover.

Patterns in greenup onset show that urban–rural differences in vegetation response are a function of land surface temperatures, showing a significant linear trend between change in greenup and change in temperature. The trend generally shows that greenup advances three days for each one degree Celsius increase in temperature. This trend was not found for onset of dormancy, suggesting, according to the researchers, a more complex relationship that is influenced not only by temperature but also by daily exposure to light and water availability. The team’s findings are reported in a recent issue of Geophysical Research Letters.

Ann Marie Menting | EurekAlert!
Further information:
http://www.bu.edu
http://www.gsfc.nasa.gov

More articles from Earth Sciences:

nachricht Predicting unpredictability: Information theory offers new way to read ice cores
07.12.2016 | Santa Fe Institute

nachricht Sea ice hit record lows in November
07.12.2016 | University of Colorado at Boulder

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>