Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


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


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:

More articles from Earth Sciences:

nachricht Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union

nachricht UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

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

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>