As if climate change and pollution weren’t bad enough, overfishing is making a mess of the Great Barrier Reef, the latest research from James Cook University in Queensland, Australia, published Tuesday, has found. Researchers discovered that the removal of certain predatory species like coral trout and snapper from the food chain has disrupted the balance between the reef’s marine residents and is changing the make-up of its fish populations, scientists say.

As one species’ numbers fell, others’ rose. Smaller species like damselfish and parrotfish were flourishing in areas where predator fish had been overfished, researchers found. Areas of the reef that were protected from fishing had up to five times as many predators as the fished areas.

While other factors certainly play a role in altering Great Barrier Reef ecosystems, the “great differences in the abundance of predatory reef fish, and of their prey, can be attributed to humans,” Mike Kingsford, the study’s co-author, said in a statement. Fortunately, there’s hope of reversing the damage. “Fishing impacts are something that we can manage fairly easily compared to other threats such as climate change and run-off pollution, which are threatening the Great Barrier Reef,” said Kingsford.

Australia’s Great Barrier Reef is the largest living structure on earth, stretching for more than 2,300 kilometers (1,430 miles) and covering an area roughly the size of Finland. Six hundred types of coral reef, 1,600 species of fish and 133 varieties of sharks and rays call the Great Barrier home. Laws were put in place in the 1970s to preserve portions of the reef.

The Great Barrier Reef fishing industry is a $1 billion business, second in profits only to tourism. Most areas of the reef are protected and therefore off-limits for fishing; however, in areas where fishing is permitted, techniques like trawling – which involves dragging massive nets through the water to trap prawns and mollusks – inevitably lead to other, larger species getting caught in the nets.

In February, scientists warned of another major factor threatening the world’s largest coral reef: dredging. The government in Queensland last year greenlighted the expansion of several coal ports near the coast that would end up dumping millions of tons of dredged material near the Great Barrier Reef. The plan sparked a national debate over the impact such a project would have on the environment. In March, the project was allowed to continue; however, the government decided to withdraw public funding.

RELATED STORIES