Economist: THE beaches near Brisbane are usually among the world’s most pristine, helping to generate tourism revenue of about A$1.3 billion ($850m) a year for Queensland’s capital and Australia’s third-largest city. But more than a week after oil gushed from a cargo ship off the city’s shoreline, many were still covered in black sludge. Apart from turning into one of Australia’s worst environmental disasters, the spillage swamped a state election campaign in Queensland where the economic policies of …