Israeli scientists predict the world's coral reefs could begin to collapse in as little as 30 years from now. Studies show the oceans are becoming increasingly acidic as they soak up manmade emissions of carbon dioxide. The Hebrew University of Jerusalem researchers say this will make it difficult for many coral organisms to produce skeletal and other hard parts. The team's work on corals in the Red Sea suggests a tipping point will be reached in between 30 and 70 years.  Then the forces of erosion eating away at corals will outstrip the organisms' ability to make the reefs.