Climate change could cause the extinction of up to a third of its parasite species by 2070, a prediction that makes parasites one of the most threatened groups of life on Earth, according to a global analysis reported Sept.6 in the journal Science Advances.

The study was conducted by an international group of researchers including UConn’s Kevin Burgio and Veronica Bueno, and indicates parasite loss could dramatically disrupt ecosystems.

Admittedly, parasites—a diverse group of organisms that includes tapeworms, roundworms, ticks, lice, fleas and other pests— have a bad reputation. They are best known for causing disease in humans, livestock and other animals.

But parasites play an important role in the ecosystem. They help control wildlife populations and keep energy flowing through food chains. Because many parasites have complex life cycles that involve passing through different host species, their diversity can be considered a sign of a healthy ecosystem, says Anna J.Phillips, a research zoologist and curator of the U.S. National Parasite Collection at the Smithsonian Institution’s National Museum of National History.

“Having parasites is a good indicator that the ecosystem has been stable,” says Phillips. “It means the system has a diversity of animals in it and that conditions have been consistent long enough for these complex associations to develop.”

To find out how climate change is likely to affect the survival of a wide range of parasite species, the researchers turned to museum collections. The U.S. National Parasite Collection, an expansive set of worms, fleas, lice and other parasites, provides a broad and deep record of different species’ occurrences around the world. The still-growing collection began in 1892 and now contains millions of organisms. Most species are represented by many specimens, meaning researchers were able to use the museum’s records to predict changes over time.

Records from the U.S. National Parasite Collection were combined with additional information from specialized databases cataloging ticks, fleas, feather mites and bee mites to enable a comprehensive global analysis.

Before they could begin their analysis, the research team needed to know exactly where each specimen came from so they could understand each species’ habitat needs.

“We needed to collect as much information about where these parasites have been found in the recent past in the form of geographic coordinates,” says Burgio, a postdoctoral fellow in Ecology and Evolutionary Biology.

In recent years it has become standard to pinpoint a specimen’s original location with GPS coordinates in collection records, but the locations associated with older specimens tend to be less precise. So the team, which included 17 researchers in eight countries, spent years tracking down the exact geographical source of specimens.

“We had to sift through tens of thousands of records from all over the world and assign coordinates to each specimen when enough information was provided,” says Burgio.

That information was essential for the current study and will also aid in future research. Once the geospatial information was complete, the data could be used to make predictions about how parasites will fare as the Earth’s climate changes. Using climate forecasts, the researchers compared how 457 parasite species will be impacted by changes in climate under various scenarios.

The analysis determined that parasites are even more threatened than the animal hosts they rely on. The most catastrophic model predicted that more than a third of parasite species worldwide could be lost by 2070. The most optimistic models predicted a loss of about 10 percent.

The study highlights the delicate position of parasites in complex ecosystems, the scientists say. While much of conservation biology focuses on single species, it is important to keep in mind the goal of conserving ecosystems as a whole.

“As long as there are free-living organisms, there will be parasites. But, the picture of parasite biodiversity in 2070 or beyond has the potential to look very different than it does today,” Phillips says.

The study was supported by the University of California, Berkeley, and the Natural Sciences and Engineering Research Council of Canada. In addition to UConn, Smithsonian Institution and the University of California, Berkeley, the research collaboration included The University of Zurich, University of California, Davis, James Cook University, Estación Biológica de Doñana (CSIC), University of Michigan, Russian Academy of Sciences, University of Alberta and University of KwaZulu-Natal.