By Tim Johnson, McClatchy Foreign Staff The Miami Herald June 02, 2013 SAN PEDRO YEPOCAPA, Guatemala -- Across Central America, even as rains arrive, many coffee plantations contain only spindly, nearly defoliated bushes, the result of a blight known as coffee leaf rust whose devastation, so far, has yet to affect the prices of premium highland coffee that baristas serve around the developed world. But while Americans have yet to feel its effects, the blight may soon prove to be as disastrous as any earthquake or volcanic eruption to afflict Central America. Already, it’s knocked nearly half a million people out of work and driven up crime. And the crisis is only beginning. It may soon send a stream of new migrants toward the United States, speed up deforestation and invigorate illicit narcotics production. It also serves as a bellwether on climate change, which appears to be causing temperatures to rise, taking plagues and infestations to higher elevations that ...