Koalas over a section of Australia’s eastern coast were formally categorized as “endangered” on Friday, as the marsupials battled bushfires, land clearing, drought, and disease. Koala populations have plummeted in parts of eastern Australia in the last two decades, according to conservationists, who fear that they are now on the verge of extinction. Sussan Ley, the Environment Minister, announced that koala populations in New South Wales, the Australian Capital Territory, and Queensland have been categorized as “endangered,” giving them a higher level of protection. Just a decade before, the k…