First and foremost it should be noted that due to their aggression and massive size, hippos are some of the most dangerous animals on earth. But beyond the safety concerns, they are also altering the environment they’ve made their home. According to the report it’s the hippo’s daily routine that’s causing problems. At night they trundle about on land grazing and during the day they pass the time relaxing and cooling off in lakes and rivers. When they submerge themselves they tend to bring organic detritus that has collected on their bodies during their nocturnal wanderings into the water with them. This acts as fertilizer for algae blooms and other disruptive natural occurrences. Their nutrient rich poop hasn’t helped the situation, either.

In their native Africa this isn’t a problem because it’s all part of an ancient ecosystem. In Colombia, however, it’s posing a danger to other plant and animal species, including humans. This problem will only compound the longer the hippos are left to proliferate. Jonathan Surin, one of the authors of the study, summed it up for Newsweek in an interview, “In the next couple of decades there could be thousands of [hippos]. This study suggests that there is some urgency to deciding what to do about them. The question is: what should that be?”

Something to think about while waiting for the next season of Narcos to drop on Netflix.