Heavy monsoon rains across Southeast Asia in recent weeks have turned Sumatra, Indonesia’s westernmost island, into one of the hardest-hit areas, in a recurring natural disaster that appears to be worsening by the season. The death toll on the island of 60 million people from a rare cyclone, which triggered floods and landslides, rose to nearly 850, with hundreds still missing, authorities said. Environmental groups say rampant deforestation has exacerbated the devastation in Sumatra. Logging