In relation to their current food supply in Cape Otway, koalas are indeed overpopulated. However, that area's population surge doesn't accurately represent the status of koalas in all of Australia, where the species has had a "vulnerable" conservation status since 2012.
The Australian Koala Foundation estimates that there could be between 43,000 and 100,000 koalas in Australia, and they've urged the government to change the koala's status to "critically endangered" in one region of the country.
Outside of Cape Otway, koalas face life-threatening challenges such as traffic, pesticides, development and mining for coal.
While the cull may make more food available for surviving koalas, it also kills off even more of the already-threatened species - two ideas that seem at odds with one another.