Reuters: David Attenborough has done more than just about anyone to teach us about our planet. As he marks the end of his sweeping natural history television series, seen by hundreds of millions of people over 30 years, the British broadcaster is fearful of what the future holds for the Earth and its inhabitants. "We’ve come to an end of a particular genre, a particular type of making programs," Attenborough told Reuters, referring to the series that began with "Life on …