The air is sweltering as Américo Mosquera trudges through a shallow river in his black rubber boots. The 62-year-old knows these muddy waters well. Like many here in Colombia’s western Chocó province, Mosquera spent years searching the riverbanks for precious metals. But not anymore. Today, he is the legal representative of a local governing council that owns a swath of land in the Colombian rainforest. The problem: Large tracts of it are controlled by armed groups who extort the locals and pollute the water in an effort to dominate the $2.4 billion illegal gold trade.