Scientists are using flora to solve one of the world’s most pressing problems: discovering and removing land mines. Danish research company Aresa has developed the BioSenser, a genetically modified tobacco plant that changes from green to red when it contacts nitrogen dioxide leached from underground explosives. The United Nations estimates that more than 110 million active land mines are scattered in 68 countries, many of them leaking harmful chemicals as they decay. Researchers drop seeds from a plane, wait 10 weeks while plants grow, then look for leaves that have changed color. The practice is a welcome alternative to past detection methods, which often involved digging up large plots of land or accidentally stepping on a mine.