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By Burt Helm Today's methods of detecting land mines has one problem: Whether accompanied by keen-nosed dogs or chemical-vapor detectors, human mine-sweepers still must step their solitary way through minefields. It's dangerous work, risking a trip of a fuse that could easily maim or kill. So to avoid that, a group of scientists is researching how to put a more nimble creature to work: the honeybee.
By conditioning a bee to think it's finding food when it senses chemicals used in explosives, a team of scientists from the University of Montana, Montana State University, and the National Oceanic & Atmospheric Administration is trying to harness the bee's acute sense of smell. The group then maps the positions of the hungry swarms, using a laser-based detection method similar to radar, called lidar. Led by researchers Jerry Bromenshenk and Joseph Shaw, the team reported its results in a recent issue of Nature's physics journal Optics Express.
450-YEAR PROJECT. The work comes as part of a push by theDefense Advanced Research Projects Agency (DARPA), which is funding the project, and other organizations to develop safer and more effective ways of detecting and removing land mines. A deadly reality in much of the developing world, land mines kill roughly 15,000 to 20,000 people each year, according to a 2003 RAND Corp. study. They can lay undetected for many years, only to be triggered by an unususpecting civilian out for a stroll.
But finding and neutralizing mines is painstaking work. According to the same study, it would take roughly 450 years to clear all the world's undetected mines.
Many mine-sweeping teams use dogs to sniff out and identify chemical byproducts of dynamite, the predominant explosive used in mines. Dogs, unfortunately, take months to train, work best for their masters only, must be walked with on a leash, and are heavy enough to detonate mines -- making sweeps a risky proposition. Bees, on the other hand, are light, work for anyone, and can be "trained" in a matter of days.
SMELLING BEE. Using bees as chemical detectors is nothing new: Since the 1980s, researchers have experimented with using them for environmental sampling. The small hairs lining a bee, which it uses to collect pollen, picks up chemical traces and biological particles as well. Bees also inhale and consume large quantities of air and water for their size, picking up chemical traces in that manner too.
With land mines, scientists are using bees' acute sense of smell. Here's how it works: Bromenshenk, an environmental chemist at the University of Montana, developed a method by which he adds traces of the explosive byproducts into the bees' food. After one or two days, the insects naturally become attracted to the smell. When released into a minefield, the bees find their way toward the mines.
Of course, they find no actual food, and after lingering disappointedly for a few seconds, they fly off. With thousands of bees flying around, however, scientists have to be able to track these swarms.
ACCURATE SENSORS. How? Bees are too small to detect either with the naked eye or high-resolution video at long ranges. So instead, the team employs a laser emitter that sweeps an area like radar or sonar. When the light hits a bee, it reflects, and sensors are able to tell by the reflection just where the bee is. After sweeping several times, the scientists are able to crunch the data and see statistically where the higher occurrences of bees are located.
In controlled situations, the method is extremely effective: Bees can detect very small traces of explosive vapors with 97% accuracy and are "wrong" -- that is, passing over a mine without noticing it -- less than 1% of the time.
The research team used Fort Leonard Wood in Missouri, an Army base that keeps a minefield for testing purposes, as its laboratory. While none of the mines on the test field have fuses or triggers, they have real explosives. "It's not deadly, but it's not the sort of place you'd want to hammer anything into the ground, either" says Shaw.
NO NIGHT FLIGHTS. In a head-to-head comparison of minesweepers vs. bees, the resulting maps were extremely similar in their findings. "We got pretty excited about the results" says Shaw, "The laser device we used wasn't even really built for this, so we'll be able to keep improving further, too."
Technical hurdles must still be overcome. Bees won't fly at night or in cold or stormy weather. Laser detection will work only in flat locations, as it bounces off any other objects that stand in its way. Researchers are working on improving the laser-detection technology.
Other groups have experimented with painting bees in fluorescent colors so they'll shine brightly when hit by a laser. Others are trying to mount tiny radio-frequency ID tags on the insects to track them. But someday soon mine-sweepers may be able to keep perfect track of these explosives-hungry bees, and do so at a very safe length for both dogs and minesweepers. Helm is a reporter for BusinessWeek Online in New York