Climate change could result in the extinction of a third of the world’s parasite species in the next 50 years, according to a study led by a UC Berkeley researcher.

Colin Carlson, a campus doctoral student studying environmental science, policy and management, has led a team of scientists over the last four years to investigate the extinction rate of parasites because of climate change. According to Carlson, a decline in the parasite population could negatively impact the environment.

“We’re talking about a massive state shift for global ecosystems, and it’s very hard to predict what the world will look like on the other side,” Carlson said.

When research began, the team found an insignificant amount of open data on parasites, so a large portion of the research involved mapping and understanding existing parasite collections, specifically the U.S. National Parasite Collection. With this data, the team then made projections about how many species are put in danger by a changing climate.

Carlson said there are 75,000 to 300,000 species of parasitic worms on the planet, most of which have not even been named. The researchers found a changing environment to result in a decline of hosts and habitable environments for parasites. The repercussions of losing a third of parasites would be unimaginable, according to Carlson.

“The key take-home message of this study … is that what climate change is doing is rearranging species interaction,” said Britt Koskella, a campus assistant professor of integrative biology unaffiliated with the study. “Any time you’re messing with what evolution has perfected over long periods of time can, in my opinion, only be more harmful than good.”

An analogy that both Carlson and Koskella drew was to the cascading effects of the loss of animals near the top of the food chain. A study published in 2011 found that when the population of these animals decreased in their ecosystem, the ecosystem saw a rise in infectious disease, an increase in carbon dioxide in the atmosphere, an increase in wildfire, increased vulnerability to invasive species and decreased biodiversity, or a combination of these effects.

“Parasites, of course, they can be bad … (but) they’re also critical components of ecosystems,” Koskella said.

Future research will have to validate the team’s predictions about the potential extinction of parasites so that it can confirm that what it thinks is happening is actually happening, according to Carlson. Carlson also emphasized the importance of funding for biological collections, adding that collections such as the U.S. National Parasite Collection will play an integral role in future research.

“Climate change is kind of a lottery,” Carlson said. “It’s always good for a small handful of species, but by and large it’s bad.”