Some Mexican groups have set up training camps and storage facilities in the jungles of Petén, a “big green hole of nothing” in northern Guatemala, according to Mr Stewart.

"Autonomous cars are the real 'green' cars," Mexican-born Rojas said. "we could use a fraction of the cars that we now have."

Mexican epiphytic orchid with glaucous gray-green leaves and lemon - to golden-yellow flowers appearing only partially opened; sometimes placed in genus Cattleya.