Climate change leading to disastrous loss of parasite species

Changing climate on earth may cause extinction of up to one-third of parasite species by 2070, according to a new study. And while parasites have a bad reputation for causing disease in humans, livestock and other animals, they play important roles in ecosystems, and their loss could dramatically disrupt ecosystems.

A parasite, in essence, is any organism that makes its living off another organism (like bedbugs, leeches, vampire fish and even mistletoe). These freeloaders have been rather successful: up to half of earth's 7.7 million known species are parasitic, and this lifestyle has evolved independently hundreds of times. But in a study published this week in the journal Science Advances, researchers warn that climate change and the loss of many types of parasite could spell ecological disaster.

"One thing we've learned about parasites in the past decade is that they're a huge and important part of ecosystems that we've really neglected for years," says Colin Carlson, a graduate student studying global change biology at the University of California at Berkeley and lead author on the study.

To find out how climate change is likely to affect the survival of a wide range of parasite species, researchers turned to museum collections – mainly the US National Parasite Collection at the Smithsonian National Museum of Natural History, a 125-year-old collection containing over 20 million organisms, which provides a broad and deep record of different species' occurrences around the world. Most species are represented by many specimens, meaning researchers can use the museum's records to investigate organisms' geographical distributions and predict changes over time.

Records from the US National Parasite Collection were combined with additional information from specialised databases cataloguing ticks, fleas, feather mites and bee mites to enable a comprehensive global analysis.

Then a team, including 17 researchers in eight countries, spent years tracking down the exact geographical source of tens of thousands of parasite specimens, adding GPS coordinates to their database wherever possible.

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 per cent.

"(Slowing climate change) has a really profound impact on extinction rates, "said Carlson. Parasites are definitely going to face major extinction risk in the next 50 years. They are certainly as threatened as any other animal group."

"Climate change has the capacity to alter nearly every dimension of biodiversity," said Nyeema Harris, an assistant professor in the Department of Ecology and Evolutionary Biology of the University of Michigan (UM).

It is the consensus of the researchers that parasites need to be included in conversations about conservation, given their delicate position in complex ecosystems as the study shows.