It may be due to global warming, but about 30 million people are facing what the UN calls a humanitarian disaster as Lake Chad, one of Africa's biggest lakes, shrinks. The very shallow lake once covered 345,000 square kilometres. But like the Aral Sea, nestled among the old Soviet republics, it is disappearing. Researchers now say it is smaller than Mauritius. The drying-up is fuelling conflict and migration, and it could disappear altogether in about 20 years, according to the US National Aeronautics and Space Administration. The Lake Chad basin is home to millions of migratory birds, along with some 20 million farmers and fishermen. The UN reckons there has been a 60% decline in fish production, along with degraded pasturelands, leading to a shortage of animal feed estimated at 45% in certain places.