Here’s the last of my essays for this year’s annual “Year in Ideas” issue of the New York Times Magazine:

Land-Mine-Detecting Plants

by Clive Thompson

This January, the Danish company Aresa Biodetection announced that it had produced an unusual new variant of thale-cress, a small flowering weed: a strain that turns red in the presence of land mines. Aresa scientists had genetically modified the weed so that it reacts to nitrogen dioxide, a gas commonly emitted by explosives. A result is a new way to detect mines: sprinkle the seeds over a suspect area, wait a few weeks for the thale-cress to grow and — presto — wherever they turn red, you have danger. ”It’s much more efficient,” says Simon Ostergaard, Aresa’s C.E.O. ”It’s very tedious to clear mines the normal way. You’re putting a stick in the ground every three centimeters. One man can sometimes only do two square meters a day.”

Given that there are tens of millions of explosives still strewn across 80 countries — killing and injuring more than 8,000 people a year — the idea has intriguing merits. The plants could help free up precious abandoned farmland by showing farmers where it is still safe to tread. What’s more, the weeds can be genetically altered to detect many other environmental hazards, like heavy metals in the soil. Still, there are plenty of hurdles: Aresa is hoping its invention will pass Europe’s strict regulations governing genetically modified crops. Critics aren’t convinced the plants are accurate enough, since land-mine clearing cannot, for obvious reasons, tolerate errors. (Worse, cows might be attracted to the weeds growing over mines, with disastrous consequences.) Nevertheless, Ostergaard says he hopes to begin trials in Africa next year. If he is successful, the symbolism couldn’t be more lovely: the brutality of land mines quelled by a humble flower.