SYDNEY - A huge cattle station that pours sediment into the Great Barrier Reef was bought Wednesday by the government as efforts are stepped up to help the World Heritage site bounce back from mass bleaching. Global warming has been wreaking havoc on the reef, contributing to an unprecedented bleaching event this year that saw much of it whiten and almost a quarter of corals die. The reef, which teems with marine life, is also under pressure from farming run-off, with the 560 square kilometre (216 square miles) Springvale Station near Cooktown in northern Queensland one of the worst culprits. Queensland Environment Minister Steven Miles said Springvale contributed huge amounts of sediment run-off to the northern part of the Barrier Reef, the worst hit by the bleaching caused by warming sea temperatures.