Katrina, Rita caused U.S.' largest tree die-off

  • Updated: November 15, 2007 - 10:09 PM

New satellite imaging has revealed that Hurricanes Katrina and Rita produced the largest single forestry disaster on record in the United States -- an essentially unreported ecological catastrophe that killed or severely damaged about 320 million trees in Mississippi and Louisiana.

The die-off, caused initially by wind and later by the pooling of stagnant water, was so massive that researchers say it will add significantly to the greenhouse gas buildup -- ultimately putting as much carbon from dying vegetation into the air as the rest of the U.S. forest takes out in a year of photosynthesis.

Also, the downing of so many trees has opened vast and sometimes fragile tracts of land to several aggressive and fast-growing exotic species that are already squeezing out more environmentally productive native species.

Efforts to limit the damage have been handicapped by the ineffectiveness of a $504 million federal program to Gulf Coast land owners to replant and fight the invasive species. Congress appropriated the money in 2005 and added to it in 2007, but officials involved with the emergency conservation program say that only about $70 million has been processed or dispensed so far. Advocates say onerous bureaucratic hurdles and low compensation rates are major reasons why.

Bengt (Skip) Hyberg, a U.S. Department of Agriculture Farm Service Agency economist and policy analyst, said changes were made in the program this year to make it more attractive to landowners. The new assessment of trees killed or severely damaged comes from a study to be released today in the journal Science.

PEER PRESSURE WORKS ON COCKROACHES, TOO

Many a mother has said, with a sigh, "If your friends jumped off a cliff, would you jump, too?" The answer, for cockroaches at least, may well be yes. Researchers using robotic roaches were able to persuade real cockroaches to do things that their instincts told them were not the best idea.

This experiment in bug peer pressure combined entomology, robotics and the study of ways that complex and even intelligent patterns can arise from simple behavior.

Jose Halloy, a biology researcher at the Free University of Brussels and lead author of a paper describing the research in today's issue of the journal Science, and his colleagues set up a cockroach arena one yard in diameter. Two 6-inch-wide plastic discs were suspended over it, providing the dark shelters that cockroaches prefer. But one disc was darker and a more likely cockroach hangout.

Roaches have weak eyes, allowing the researchers to create a robotic roach that resembles a mini golf cart more than an insect. They doused the robots with roach sex hormones to make them smell acceptable.

When 16 cockroaches were placed in the arena, they naturally gravitated toward the darker disc, following what the researchers believe is an internal calculation of the amount of light and the number of other roaches.

Halloy then replaced four of the cockroaches with four robots equipped with sensors to measure light and the proximity of other robots. When the robots emulated the real roaches, the group continued to seek the dark place. When the four robots were reprogrammed to prefer the lighter disc, however, the real roaches followed them about 60 percent of the time, in essence deferring their own judgment as the preference grew more popular.

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