Less than twenty per cent of the world’s oceans have been explored so far. That is not a lot. But it is enough for us to know that the oceans are threatened by global warming, acidification, and pollution. Coral bleaching is just one illustration of the decline of marine ecosystems. The consequences are not just environmental. Nearly three billion people depend directly on marine and coastal biodiversity for their survival. By 2050, coastal areas that are home to300 million people could be threatened by rising sea levels due to climate change.