Australia’s Great Barrier Reef, the world’s largest coral reef system, home to thousands of animals, and one of Australia’s most iconic tourism destinations is being devoured by dozens of crown-of-thorns starfish. According to The New York Times, these starfish typically keep the reef in check by eating the coral that grows quickly, but recently there has been an outbreak and they are consuming coral faster than it can grow back.

So, what caused this outbreak? Scientist still aren’t sure, but they have many possible answers. According to Reef Resilience Network, one explanation has to do with the amount of food available to the starfish. For example, when there is a plankton bloom (a high concentration of phytoplankton), the crown-of-thorns’ larvae have an elevated amount of food, which allow more of them to survive. According to the Great Barrier Reef Marine Park Authority, another hypothesis is overfishing of the starfish’s main predator, the giant triton snail. In addition to the triton, the reef is home to many other, more common fish that will feed on young starfish, however are not as important as the effect of the snail. Lastly, according to Oceana, it is important to note that crown-of-thorn starfish are typically more harmful to the reef if the coral is already strained from coral bleaching or other environmental factors.

The decline of coral has impacts on other animals too. According to The New York Times,  thousands of species like sharks, turtles, and whales live in the reef. Also, the reef is responsible for 70,000 of the jobs in Australia, and billions of dollars annually in tourism revenue. Therefore, if Australia lost the coral in the Great Barrier Reef, it could also lose thousands of jobs and lots of money from their tourism industry. Luckily, various control measures have been put into effect. According to the Australian Institute of Marine Science, one way to keep the population in check is to insert poison into the starfish; this will kill the starfish without damaging other reef creatures. Next, according to Reef Resilience Network, building underwater fences is another method of control. Protecting crown-of-thorn predators, like the giant triton, is the final and most natural solution to their overpopulation.

This isn’t the first time that there has been an outbreak of the crown-of-thorn species. In fact, according to the Great Barrier Reef Marine Park Authority, outbreaks happen roughly every 17 years. Since the 1960s, there have been four documented outbreaks. The first was in 1962 and the last in 2010. The worst one however, occurred between 1985 and 2012 during which it is believed that the reef lost about 50 percent of its coral cover. Nonetheless, the reef has always managed to successfully recover, so there is a likely chance it will do the same this time.