BOGOTA, Colombia — Armed groups operating in Colombia’s Amazon are tightening their grip on the region and that’s stalling government efforts to tackle deforestation, according to a think tank report Thursday. The Revolutionary Armed Forces of Colombia (FARC) dissidents, known as EMC, have the ability to slow or accelerate deforestation at will, said the report by The International Crisis Group. Some of the former FARC members never signed and disagree with the 2016 FARC-Colombia peace deal. Others signed it but took up arms again, while others are new to the dissident ranks either as volunteers or forced fighters, said Rodrigo