Beavers and the dams they build are not always embraced in the areas where they do their work. But there's a growing recognition that they also are building a kind of natural infrastructure that helps with water management and the climate. Science correspondent Miles O'Brien went to see the beavers at work during their busy season and has the story for our ongoing coverage of Tipping Points. PBS News is supported by - https://www.pbs.org/newshour/about/funders