Cleaning up the Killing Fields

BOGOTÁ—Fernando Cristancho watches nervously as a remote-controlled, Jeep-like contraption with six wheels inches across a denuded field laid with land mines. The nuclear physicist and his colleagues at the National University of Colombia here built the vehicle themselves, and this foray at a military test facility near Bogotá is its debut outside the lab. Extending from its frame is a metal arm that sweeps in a semicircle as the machine advances. The arm carries a neutron source and detectors designed to record the number and speed of the neutrons ricocheting off hidden objects such as mines—revealing them from a safe distance, Cristancho hopes.

The mines at the test field are disarmed. But across Colombia, land mines killed or injured more than 11,500 people during a decades-long war between the government and the Revolutionary Armed Forces of Colombia (FARC), and a 2016 peace deal has not eliminated the threat. Mines continue to kill or maim dozens each year, and in rural areas, they keep villagers who fled during the conflict from returning home. To tackle the scourge, Colombia has committed to ridding itself of land mines by 2021.

"There's still a huge amount to work to do," says Nestor Peña, an electrical engineer at the University of the Andes (Uniandes) here. So far, only 11% of an estimated 52 square kilometers littered with mines has been cleared. The going is slow, he says: "Techniques that are well-established for conventional wars haven't worked in Colombia." Worldwide most land mines are military-grade and can be spotted with metal detectors. In Colombia, the FARC and other armed groups crafted low-tech improvised explosive devices (IEDs) from PVC pipes, plastic soda bottles, and other hard-to-detect containers packed with explosives and attached to a detonator. "These IEDs are designed to be hard to find," says Chris Ince, the Colombia program manager for the HALO Trust, a humanitarian demining agency here. Colombia's rugged terrain, wet climate, and lush forests also make demining a stiff challenge.

Protocols to find and disarm those sorts of homemade mines require painstakingly clearing vegetation and then removing, millimeter by millimeter, the top 15 centimeters of soil to expose mines. That process is invasive—and possibly harmful—to Colombia's rich biodiversity. One fragile ecosystem is the páramo, an otherworldly high-altitude meadow that includes Chingaza national park, near the capital. The park's eastern half, riddled with mines, is closed to visitors. Demining there could damage the thick, porous soil that collects and filters the freshwater that Bogotá relies on.

So Cristancho and others are seeking less arduous and destructive ways to do the job. Electrical engineers at the National University are testing a stationary detector featuring ground-penetrating radar, which could find mines from a distance through thick vegetation. At Uniandes, Peña and his colleagues try to help mine-sniffing dogs work more efficiently. Upon catching a whiff of an explosive, the dog sits—and for now, its handler must be close enough to see it, making for slow progress when land mine density is low, as it usually is in Colombia. The Uniandes engineers are testing devices that can inform handlers what their dogs are doing up to 300 meters away, allowing the dogs to roam.

"The combination of various techniques is what's going to increase efficiency and decrease the time [demining] takes," says Diego Torres, a nuclear physicist working with Cristancho at the National University. But Ince points out that Colombia's 2021 target doesn't leave much time to vet and deploy techniques.

At the proving ground, Cristancho's neutron-based minesweeper detects every one of the neutered mines. "The thing works," he says, with relief. But he worries about how the vehicle will perform when up against the different moisture levels across Colombia's diverse soils. No new demining technology has ever been tested in such challenging conditions, Cristancho says. "There are no research protocols for this."