The ravages of colonialism cast a dark pall over the stunning South American landscape in “Embrace of the Serpent,” the latest visual astonishment from the gifted Colombian writer-director Ciro Guerra. Charting two parallel journeys deep into the Amazon, each one undertaken by a European explorer and a local shaman, this bifurcated narrative delivers a fairly comprehensive critique of the destruction of indigenous cultures at the hands of white invaders, and if Guerra somewhat exhausts his insights before the end of its two-hour-plus running time, there’s no denying the film’s chastening moral conviction or the transfixing power of its black-and-white imagery. At once blistering and poetic, not just an ethnographic study but also a striking act of cinematic witness, “Serpent” should continue to garner critical and audience acclaim on the festival trail following its top Directors’ Fortnight prize at Cannes.