Featured Research

from universities, journals, and other organizations

Spring Through Fall, Cities Are Greener Longer Than Neighboring Rural Regions

Date:
July 29, 2004
Source:
Boston University
Summary:
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.

Boston -- 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.

Related Articles


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.


Story Source:

The above story is based on materials provided by Boston University. Note: Materials may be edited for content and length.


Cite This Page:

Boston University. "Spring Through Fall, Cities Are Greener Longer Than Neighboring Rural Regions." ScienceDaily. ScienceDaily, 29 July 2004. <www.sciencedaily.com/releases/2004/07/040729091822.htm>.
Boston University. (2004, July 29). Spring Through Fall, Cities Are Greener Longer Than Neighboring Rural Regions. ScienceDaily. Retrieved October 24, 2014 from www.sciencedaily.com/releases/2004/07/040729091822.htm
Boston University. "Spring Through Fall, Cities Are Greener Longer Than Neighboring Rural Regions." ScienceDaily. www.sciencedaily.com/releases/2004/07/040729091822.htm (accessed October 24, 2014).

Share This



More Earth & Climate News

Friday, October 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

EU Gets Climate Deal, UK PM Gets Knock

EU Gets Climate Deal, UK PM Gets Knock

Reuters - Business Video Online (Oct. 24, 2014) EU leaders achieve a show of unity by striking a compromise deal on carbon emissions. But David Cameron's bid to push back EU budget contributions gets a slap in the face as the European Commission demands an extra 2bn euros. David Pollard reports. Video provided by Reuters
Powered by NewsLook.com
Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Reuters - Innovations Video Online (Oct. 24, 2014) Miniature deep sea animals discovered off the Australian coast almost three decades ago are puzzling scientists, who say the organisms have proved impossible to categorise. Academics at the Natural History of Denmark have appealed to the world scientific community for help, saying that further information on Dendrogramma enigmatica and Dendrogramma discoides could answer key evolutionary questions. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Raw: Tornado Rips Roofs in Washington State

Raw: Tornado Rips Roofs in Washington State

AP (Oct. 24, 2014) A rare tornado ripped roofs off buildings, uprooted trees and shattered windows Thursday afternoon in the southwest Washington city of Longview, but there were no reports of injuries. (Oct. 24) Video provided by AP
Powered by NewsLook.com
Fast-Moving Lava Headed For Town On Hawaii's Big Island

Fast-Moving Lava Headed For Town On Hawaii's Big Island

Newsy (Oct. 24, 2014) Lava from the Kilauea volcano on Hawaii's Big Island has accelerated as it travels toward a town called Pahoa. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins