The FARC guerrillas once protected the Amazon rainforest in Colombia Carlos Villalon / Redux / eyevine

AS RAIN lashes down on San José del Guaviare, Angélica Rojas Moncada of the Foundation for Conservation and Sustainable Development breathes a sigh of relief. “Thank God,” she says. “There are already three fires burning today. Hopefully this does the trick.”

Guaviare province is on the boundary between Colombia’s plains and the Amazon rainforest. But over the past century, the forest has been pushed back by a series of economic booms. From rubber to marijuana and coca, new opportunities have eaten into the …