BBC: A healthy fish population could be the key to ensuring coral reefs survive the impacts of climate change, pollution, overfishing and other threats. Australian scientists found that some fish act as "lawnmowers", keeping coral free of kelp and unwanted algae. At a briefing to parliamentarians in Canberra, they said protected areas were rebuilding fish populations in some parts of the Great Barrier Reef. Warming seas are likely to affect the reef severely …