The world’s parasites are going extinct – Here’s why that’s a bad thing

Desdemona Despair

By Ben Panko
7 September 2017

(Smithsonian) – What if the world’s parasites suddenly went extinct? Given how much work we’ve put into combating malaria-carrying mosquitoes and horrifying Guinea worms, it sounds like a reason for celebration. But think twice: Actually, losing these much-despised mooches, bloodsuckers and freeloaders could have disastrous consequences for the environment and human health.

A parasite, in essence, is any organism that makes its living off another organism (think bed bugs, 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 could drive up to one-third of Earth’s parasite species to extinction by the year 2070.

That kind of mass die-off 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.

Carlson had experience researching how climate change is driving the current spate of species die-offs. But four years ago, he saw the potential to look into a lesser known group: parasites. “There has been a lot of work that’s been done in the late couple of decades focused on understanding why big mammals go extinct, or how crops respond to climate change,” Carlson says, “but there’s a lot of types of animals and plants that we don’t know a lot about.”

He formed a team to find out more about how parasite species could feel the heat in the coming decades. The team based their predictions for this research on a “deceptively simple model” from a landmark 2004 study in the journal Nature, which connected species extinction rates to how much of their habitat they’re expected to lose. “The problem is, we don’t know very much about where parasites live,” Carlson says. [more]

The World’s Parasites Are Going Extinct. Here’s Why That’s a Bad Thing

ABSTRACT: Climate change is a well-documented driver of both wildlife extinction, and disease emergence, but the negative impacts of climate change on parasite diversity are undocumented. We compiled the most comprehensive spatially explicit data set available for parasites, projected range shifts in a changing climate, and estimated extinction rates for eight major parasite clades. On the basis of 53,133 occurrences capturing the geographic ranges of 457 parasite species, conservative model projections suggest that 5 to 10% of these species are committed to extinction by 2070 from climate-driven habitat loss alone. We find no evidence that parasites with zoonotic potential have a significantly higher potential to gain range in a changing climate, but we do find that ectoparasites (especially ticks) fare disproportionately worse than endoparasites. Accounting for host-driven coextinctions, models predict that up to 30% of parasitic worms are committed to extinction, driven by a combination of direct and indirect pressures. Despite high local extinction rates, parasite richness could still increase by an order of magnitude in some places, because species successfully tracking climate change invade temperate ecosystems and replace native species with unpredictable ecological consequences.

Parasite biodiversity faces extinction and redistribution in a changing climate