Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Land cover changes affect US summer climate

25.03.2004


While climate may be impacted by carbon dioxide emissions, aerosols and other factors, a new study offers further evidence land surface changes may also play a significant role.


Changes in Vegetation across the United States

These images show the (a) dominant vegetation type and (b) fractional areal coverage (%) of each grid cell by the dominant vegetation for the 1700, 1910, and 1990 vegetation cases.

The maps labeled 1700 are estimates of potential vegetation for the country under current climate conditions (i.e., without land use). Maps labeled 1910 and 1990 are estimates of land cover for those periods that include the effects of land-use history up to and including those years respectively.

These figures illustrate some of the large changes to the land cover patterns that are estimated to have occurred across the United States as the result of land-use activities. It can be seen that between 1700 and 1910, much of the U.S. was converted from forests to croplands. By 1910, forest cover over the United States was at or near its lowest point in 300 years. Since 1910, agriculture has substantially intensified in the central and western U.S., but decreased in the east. By 1990, croplands covered about 24 percent of the total land area, with farms occupying more than 90 percent of some regions in Iowa and eastern Nebraska. Forest cover has steadily increased, to near 40 percent of the total land area in 1990. CREDIT: Somnath Baidya Roy, Princeton University



The study of summer climate in the United States reported changes in land cover, particularly vegetation, have impacted regional temperatures and precipitation. The study used data and computer models from NASA and other organizations such as the National Oceanic and Atmospheric Administration (NOAA).

"The largest human impacts on nature have occurred since the Industrial Revolution," said Somnath Baidya Roy, a research scientist at Princeton University, N.J. Roy is lead author of the study published in a recent issue of the Journal of Geophysical Research-Atmospheres. Co-authors included George Hurtt, University of New Hampshire; Christopher Weaver, Rutgers University; and Stephen Pacala also from of Princeton.


Previous studies simulated and compared past and present climates with current and potential vegetation. This research used the NASA-funded Ecosystem Demography computer model to trace the evolution of vegetation distribution patterns over the U.S. for nearly 300 years. "The model is truly a technological breakthrough and enables scientists to study the potential impact of land use and climate change across a wide range of scales, from individual plants to continental regions," Hurtt said.

The researchers found land cover changes produced a significant cooling effect of more than one degree Fahrenheit in parts of the Great Plains and Midwest as agriculture expanded and replaced grasslands. Farmlands tend to create lower temperatures through increased evaporation. A warming effect was found along the Atlantic coast where croplands replaced forests.

Compared to forests, croplands are less efficient in transpiration; a daytime process where water evaporates from leaves during photosynthesis and cools the air. A slight warming effect was also observed across the Southwest, where woodlands replaced some deserts.

The study found land cover changes could impact local precipitation, but not as significantly as they affect temperature. The relatively strong cooling over the central U.S. has probably weakened the temperature difference between land and the Gulf of Mexico, slowing the northern movement of weather systems and resulting in enhanced rainfall across Texas. Consequently, the air masses reaching the Central Lowlands region, including Illinois and Indiana, are drier, causing rainfall reductions.

"Land cover change is not uniform. Most people associate land cover change with deforestation, but the changes in the U.S. are more complex, creating a temperature signal that is more difficult to study," Roy said. The forest cover in the U.S. has actually increased in the last 100 years mainly due to farm abandonment in the East, fire suppression in the West, and large parts of the Great Plains have been converted into irrigated croplands, which tends to produce cooling.

The research also carries additional implications. "It is important to understand the effects of changing land cover, because it can mitigate or exacerbate greenhouse warming," Roy said. "In the U.S. over the past 100 years, it seems to be offsetting greenhouse warming. The opposite is probably true in most other parts of the world. This finding has also been supported in previous research," Roy said.

Researchers relied on several computer models. These included the Ecosystem Demography model, which incorporates data from NASA’s International Satellite Land Surface Climatology Project. The model contains data from the Global Energy and Water Cycle Experiment. The experiment was conceived to take advantage of environmental monitoring satellites including NASA’s Terra, Aqua, Tropical Rainfall Measuring Mission, and ADEOS I and II. The study also used the Regional Atmospheric Modeling System for regional climate simulations.

Rob Gutro | GSFC
Further information:
http://www.gsfc.nasa.gov/topstory/2004/0223landsummer.html
http://www.earth.nasa.gov

More articles from Earth Sciences:

nachricht Climate Change in West Africa
17.06.2019 | Julius-Maximilians-Universität Würzburg

nachricht Determining the Earth’s gravity field more accurately than ever before
13.06.2019 | Technische Universität Graz

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Successfully Tested in Praxis: Bidirectional Sensor Technology Optimizes Laser Material Deposition

The quality of additively manufactured components depends not only on the manufacturing process, but also on the inline process control. The process control ensures a reliable coating process because it detects deviations from the target geometry immediately. At LASER World of PHOTONICS 2019, the Fraunhofer Institute for Laser Technology ILT will be demonstrating how well bi-directional sensor technology can already be used for Laser Material Deposition (LMD) in combination with commercial optics at booth A2.431.

Fraunhofer ILT has been developing optical sensor technology specifically for production measurement technology for around 10 years. In particular, its »bd-1«...

Im Focus: The hidden structure of the periodic system

The well-known representation of chemical elements is just one example of how objects can be arranged and classified

The periodic table of elements that most chemistry books depict is only one special case. This tabular overview of the chemical elements, which goes back to...

Im Focus: MPSD team discovers light-induced ferroelectricity in strontium titanate

Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.

Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...

Im Focus: Determining the Earth’s gravity field more accurately than ever before

Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.

The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...

Im Focus: Tube anemone has the largest animal mitochondrial genome ever sequenced

Discovery by Brazilian and US researchers could change the classification of two species, which appear more akin to jellyfish than was thought.

The tube anemone Isarachnanthus nocturnus is only 15 cm long but has the largest mitochondrial genome of any animal sequenced to date, with 80,923 base pairs....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

 
Latest News

A new force for optical tweezers awakens

19.06.2019 | Physics and Astronomy

New AI system manages road infrastructure via Google Street View

19.06.2019 | Information Technology

A new manufacturing process for aluminum alloys

19.06.2019 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>