New weed may flag land mines

A weed that turns red when it grows near land mines could help clear dangerous fields in war-torn countries such as Bosnia, Iraq, and Afghanistan. The genetically modified Thales cress is sensitive to nitrogen dioxide, a byproduct of mines, and changes from green to red when the gas is present in soil.

Currently, mines can be detected only by human or canine probing. Scientists hope the plant will show where the land mines are so they can be removed safely, greatly reducing fatalities and injuries among those who hunt for mines and the unsuspecting public.

Danish biotechnology company Aresa Biodetection, which is creating the genetically altered plant, hopes to start selling it within a few years, after researchers complete field tests on its effectiveness.

Lab results so far look promising, says Simon Oestergaard, chief executive of Aresa. He envisions that the plant will be used mostly to clear fields suitable for farming. "The main target of this product is soil that will be used for different agricultural activities," he says.

Some 110 million land mines are hidden in 45 countries. Many of them have been buried for years. It will cost $33 billion to remove them and take 1,100 years under present demining rates, according to the United Nations. It estimates that governments spend $200 million to $300 million on the removal and detection of 10,000 mines each year.

In addition, the Red Cross estimates that 26,000 people are killed or injured each year by leftover mines. Large areas, as much as 40 percent of all land in Cambodia and 90 percent in Angola, go unused because of land mines.

Currently, explosives experts remove mines by putting a stick into the ground to locate them. They then excavate and detonate them. They also use dogs and metal detectors, but these approaches can be dangerous: For every 5,000 mines removed, one explosive expert is killed and two others are seriously injured, according to the Vietnam Veterans Foundation of America.

Researchers hope the modified Thales cress will offer an easier and safer method of detection. Its seeds can be sprayed over fields from planes or via spray guns at a cost significantly less than conventional methods.

Three to six weeks after the plant is sowed over an area, its leaves turn red, its normal autumn color, to signal the approximate location of mines.

"They are easy to spot," says Carsten Meier, a former University of Copenhagen researcher who serves as scientific adviser to Aresa. The method can be introduced in different plants, but researchers chose the Thales cress because it grows naturally worldwide and has a growth cycle of six to eight weeks.

One concern, however, is that the weed is shallow-rooted, so it would not be able to detect deeply planted mines. But most mines are found closer to the surface, says Geir Bjoersvik of the mine action unit at Norwegian Peoples Aid in Oslo.

Field tests, scheduled to start in Denmark this spring and in other countries soon after, will determine how sensitive the plant is to nitrogen dioxide and how much of the gas is required to make it turn red. So far, the plant has shown signs of being oversensitive. "It's better to have a red spot and check it and find there isn't a mine than miss one that's there," Dr. Meier says.

The plant is self-pollinating. Researchers also removed the gene for an important growth hormone, which eliminates the risk of spreading pollen to unmodified plants because the new weed neither germinates nor sets seeds unless a specific fertilizer is used.

But relying solely on a weed to detect land mines raises certain concerns. Some mine casings are sealed to prevent the escape of nitrogen dioxide, which means not all explosives could be detected by the plant, saysBob Gravett, senior technical adviser to the Mines Advisory Group, an international organization that removes land mines. In addition, the Thales cress plant might attract livestock into dangerous areas before mines are cleared.

A further genetic modification of Thales cress may enable the plant to detect and clean soil contaminated by heavy metals and other sources of pollution, but research is just beginning in this area.

Oestergaard says a prototype of the mine-clearing version could be ready to sell in a few years.

"This is a great idea," says Richard Vierstra, a horticulture scientist at the University of Wisconsin in Madison.

But biotechnology alone may not solve the problem of land mines. "Political will, economic will, and technological will are all necessary, as well as putting words into a broader context by having a ban on land mines," says Susan Walker of Handicap International, which is working in 38 countries to aid mine victims.