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News Tip


December 9, 2003

For more information on these science news and feature story tips, contact the public information officer listed at (703) 292-8070. Editor: Josh Chamot

Detecting Terrorists and Other Hidden Groups on the Internet

In the free-form clamor of the Internet's discussion groups and other public forums, researchers at Rensselaer Polytechnic Institute want to listen for the whispers of groups trying to stay hidden.

Since September 11, 2001, some have feared that general-interest Internet forums could be co-opted by terrorist groups to camouflage coded messages. To detect those groups amidst unrelated Internet traffic, the RPI team has combined statistical learning algorithms, graph theory, social network theories and other methods to trace the patterns of message exchange and study how they evolve.

From the evolving patterns alone—and without the need to read or understand the messages themselves—they can reverse-engineer the social networks that form naturally among discussants, as well as the messages exchanged among the members of groups that had been concealing their communications.

Mark Goldberg, Bulent Yener, William Wallace, Malik Magdon-Ismail and Mukkai Krishnamoorthy were recently awarded a $550,000 National Science Foundation (NSF) Information Technology Research award to expand techniques developed with an earlier grant and make them practical for real-world Internet discussion groups.

In addition to identifying hidden groups, the techniques could also be used to help system administrators efficiently allocate resources for active forums, model the spread of e-mail viruses and develop appropriate reactions, and suggest ways to alter membership policies to promote better online behavior.

NSF Media Contact: David Hart, (703) 292-7737,
NSF Science Expert: Suzanne Iacono, (703) 292-8930,
Principal Investigator: Mark Goldberg, (518) 276-2609,
NSF Award #0324947

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Environmental Changes Affect Plant Diversity

If humans tinker with nature, believed legendary ecologist Aldo Leopold, it is always best to keep all the parts. In ecology, "all the parts" is the diversity of species that live in an ecosystem. Until recently, however, little attention was paid to the potential ecological effects on plant diversity from global environmental changes, including increased warming from climbing levels of atmospheric carbon dioxide, elevated nitrogen pollution and increased precipitation.

Now, scientists funded by NSF have discovered that large-scale environmental changes can quickly alter an ecosystem.

Understanding what might happen to ecosystems influenced by climate and atmospheric changes is a significant question for biologists. Scientists affiliated with the University of California at Santa Cruz, Stanford University and the Carnegie Institution of Washington conducted a three-year study in the Jasper Ridge, California, Biological Preserve, a grassland in which 43 species of plants grow as a mixture of grasses and wildflowers.

According to scientist Chris Field of the Carnegie Institution, the researchers simulated a series of possible future environments for Jasper Ridge, with multiple changing factors: increased warming from higher atmospheric carbon dioxide; pollution from excess nitrogen reaching the environment from fertilizers and other sources; and increased precipitation. Different combinations of these variables are most likely to reflect what future conditions at Jasper Ridge might be like, says Field.

Researcher Erika Zavaleta of the University of California at Santa Cruz, lead scientist on the study, says that at the end of the three-year project, three experimental treatments changed the total plant diversity.

Increased carbon dioxide and increased nitrogen reduced plant diversity at Jasper Ridge, while more water (from simulated rainfall) increased plant diversity. Warming temperatures alone had no effect.

The researchers note that wildflower diversity decreased in the study, but total plant diversity was not affected as there was an increase in grasses. The largest loss of wildflower diversity resulted from increased carbon dioxide, coupled with elevated nitrogen and higher temperatures.

"Given the importance of these wildflower species for wildlife, nutrient cycling and natural beauty, the losses under realistic global [climate] changes are cause for concern," says Zavaleta.

NSF Media Contact: Cheryl Dybas, (703) 292-7734,

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Coastal Marsh Grasses are Dying in the South

Reports of salt marsh grass dieback in Georgia began in the spring of 2002, and there are now large areas of marsh with little or no live above-ground vegetation say scientists Merryl Alber and James Hollibaugh of NSF's Georgia Coastal Ecosystems LTER (Long-Term Ecological Research) site.

All Georgia coastal counties are reporting such marsh diebacks, and while some areas are showing signs of recovery, others have shown no regrowth since observations began a year ago. Current estimates exceed 1,000 affected acres, with both Spartina alterniflora (salt marsh cord grass) and Juncus romerianus (black needlerush) declining. Once the plants die, says Hollibaugh, their roots and rhizomes decompose, and "the marsh is down to bare mud."

It is not clear, say these scientists, whether this die-off is the same as the brown marsh phenomenon that has occurred in the Gulf of Mexico region. Although some aspects of the situation are similar, such as both occurring during periods of prolonged drought, there are differences between the sites.

Plants in Louisiana go through a progressive color change, from green to brown, and are left standing after a dieback, but in Georgia researchers have not seen standing dead plants. In Louisiana, only Spartina is affected; in Georgia, both Spartina and Juncus are affected. Louisiana dieback areas are often located in the marsh interior, but in Georgia they are in both creekbank and high marsh areas.

Researchers have proposed several theories to explain the dieback, including the presence of an unusual fungal population (none was found) or the effects of drought. Scientists have planned a workshop to further investigate reasons for the marsh grass loss.

Whatever the cause, say Hollibaugh and Alber, "the areas that have already been affected will not completely regenerate and will likely require replanting. We're in danger of losing this habitat due to erosion."

NSF Media Contact: Cheryl Dybas, (703) 292-7734,

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