Imagine a tropical island, the remote location of which has left it relatively untouched by humans. Animals, both terrestrial and marine, flourish here. Pollution doesn’t exist and ecosystems are thriving.

If it sounds too good to be true, well, that’s because it sort of is.

Thousands of miles away from any major land mass, the Chagos archipelago was believed to be one of those pristine and untouched places, but a new study published in Science Advances suggests otherwise.

Declining shark populations show that even in one of the most remote coral reef systems on the planet, humanity is leaving its mark.

Humans have been visiting the archipelago around it for hundreds of years and have kept records of fish and shark population estimates, which include the first scientific survey that took place here in 1948, catch records going back 50 years, and surveys conducted by scuba divers in the 1970s. Researchers used this data to predict what shark populations should have been without human impact.

The study showed the sharks weren’t as abundant as they were originally believed to be. Of two dominant sharks, there were an estimated 571,310 gray reef sharks and almost 32,000 silvertip sharks – 93 percent lower than the predicted level.

Researchers say it means this area has been exploited longer and more intensely than previously thought, and it is almost certainly because of overfishing.

More than half of the world’s waters are being commercially fished, and researchers say it’s likely this overfishing is depleting shark populations, and removing an ecosystem’s dominant species can have a lasting impact. Since sharks don’t reproduce in large numbers and it takes them a long time to mature, when their populations decline they can have a more difficult time bouncing back.  

Every year humans kill an estimated 100 million sharks, and illegal shark fishing is thought to occur globally, even in marine sanctuaries and reserves. 

It appears even the most remote animals can’t escape human’s obsession with plastics. Researchers say they found garbage throughout the reefs. That’s no surprise considering plastic is found in nearly every body of water and on nearly every continent.

The researchers say this is an important lesson in how looks can be deceiving.