According to a massive new analysis of poisonous or venomous aquatic animals, dangerous species might become increasingly common in new ranges. Species whose ranges might shift polewards due to warmer water include lionfish, sea snakes, crown-of-thorns starfish and a number of different types of venomous jellies.

“These species have human interest because they’re poisonous but they reflect the broader patterns that we’re seeing—range shifts, abundance changes, either declines or increases—and that is upsetting the balance of what we would normally see in the ecosystem,” says Isabelle Neylan, a PhD student in marine sciences at the University of California, Davis and a coauthor of the study recently published in Wilderness and Environment Medicine.

She and her coauthors scoured medical, environmental and ecological research on the effect of climate change on poisonous and venomous creatures as well as various modeling studies and poison center data. The recent paper actually represents the second part of the research—the first study published earlier this year focused on the effect climate change might have on poisonous and venomous land creatures.

She says that most species may not necessarily see an increase in abundance, but will see their ranges shift as waters become too warm closer to the equator, pushing them northwards or southwards following their ideal temperature niches. However, not all species will experience this evenly as some will not be able to cope with these range shifts.

“The big pattern is that there isn’t necessarily a pattern,” says Neylan, who conducted these studies while she was a research technician at the University of North Carolina at Chapel Hill, adding that each species may experience unique challenges in terms of changes in distribution or population.

Lions, jellies, and starfish oh my

One group of animals that are most likely to increase both in range and abundance due to warmer waters and changes in the acidity level of the ocean are jellyfish. These include the deadly irukandji and box jellyfish, which have been responsible for increasing amounts of deaths in Australia and may be moving southwards into more populated areas as the climate warms.

“Box jellyfish are very venomous—possibly the most venomous in the world pound-for-pound,” says Timothy Erickson, a physician and toxicologist at Brigham and Women’s Hospital and Harvard Medical School and a coauthor of the study with Neylan.

Jennifer Purcell, a research associate at Western Washington University, has studied the spread of jellyfish but was not involved in this recent study. She says that the reproduction of jellies increases in warmer waters.

“It’s not just a couple [species]—it’s really the majority of jellyfish that have been looked at which increase their abundance,” she says.

She agrees that jellyfish might be a problem due to climate change, but adds that other factors may be at play in the spread of these species such as humans releasing or moving them around, either on purpose or inadvertently.

“The jellyfish is maybe their strongest case but I do worry that they picked out some sensational species to try to make an important sounding story,” she says.

While they initially spread to Florida due to their release by pet owners, lionfish have begun to spread up the Atlantic coast to Georgia and the Carolinas. These fish, which apparently actually taste quite good themselves, can decimate small fish and marine creature populations and pack a painful sting for humans who encounter them.

Crown-of-thorns starfish have begun spreading from their traditional range in the Indo-Pacific waters southwards into the Great Barrier Reef off the coast of Australia due to an increase in temperature in those waters. These voracious toxic starfish can eat through entire reef systems. For the people who accidentally run into them while swimming or other activities, they can cause pain, inflammation, and infection.

Other fish like porcupinefish have also been sighted in new areas, but the authors note a lack of data on how climate change is affecting the range or abundance of one of the fish which humans have the most run ins—stingrays. They call for more research into the ranges and effects of shifting weather patterns on stingrays, stonefish, and blue-ringed octopus in order to understand potential problems in the future.

A toxic situation

Not all toxic aquatic species will fare well due to climate change. While sea snakes have also been found in new ranges or in increasing abundance in South Korea, California, and Hawai’i, the researchers report that the abundance of some of the most poisonous snakes in the world on land or water is decreasing worldwide.

Jellyfish 101

Poison frogs may fare the worst due to their sensitivity to temperature shifts. And it’s not just a drop in abundance. Neylan also notes that some species are going extinct due to a combination of climate change and pathogens like the chytrid fungus, which is also spreading due to climate change.

“Diversity is going down overall and that’s a bad thing,” Neylan says, adding that when species like lionfish move into new ranges with little or no predators, they can negatively impact ecosystems.

“Any change in the ecosystem has rippling effects,” Neylan says.

Unprepared hospitals

Erickson says that with the spread of poisonous creatures into new ranges, hospitals and health care systems may not know how to cope with the influx of potential sting or bite victims.

This could lead to increasing costs of health care. “Some of the antidotes are very expensive,” Erickson says, adding that these problems will likely strike poorer countries even harder as a result.

Where possible, he says that hospitals may have to have better plans in place for getting the antidotes they lack. He also notes the need for better public information about what kind of immediate steps to take, such as putting vinegar on jellyfish stings or hot water for stingray and lionfish stings.

According to the researchers, the problem is only going to be exacerbated in the future as more and more people move into coastal areas. They note that by the end of the century, 50 percent of the world’s population will be living within 60 miles of a coastline.

“There are more and more people going in the water,” Purcell agrees.