Guest essay by Eric Worrall
Back in 2013 I celebrated that Australia’s unusually hot, dry Summer meant a lower risk of deadly tick bites, but apparently this is now a bad thing.
Climate change could wipe out a third of parasite species, study finds
Parasites such as lice and fleas are crucial to ecosystems, scientists say, and extinctions could lead to unpredictable invasions
Thursday 7 September 2017
Climate change could wipe out a third of all parasite species on Earth, according to the most comprehensive analysis to date.
Tapeworms, roundworms, ticks, lice and fleas are feared for the diseases they cause or carry, but scientists warn that they also play a vital role in ecosystems. Major extinctions among parasites could lead to unpredictable invasions of surviving parasites into new areas, affecting wildlife and humans and making a “significant contribution” to the sixth mass extinction already under way on Earth.
The new research, published in Science Advances, used the collection of 20m parasites held at the Smithsonian Institution’s Museum of National History in the US to map the global distribution of 457 parasites. The scientists then applied a range of climate models and future scenarios and found that the average level of extinctions as habitats become unsuitable for parasites was 10% by 2070, but extinctions rose to a third if the loss of host species was also included.
“Parasites are obviously a hard sell,” said Carlson. “Even if you are grossed out by them – and there are obviously downsides for individual hosts and for humans – parasites play a huge role in ecosystems.” They provide up to 80% of the food web links in ecosystems, he said. Having a wide range of parasites in an ecosystem also means they compete with one another, which can help slow down the spread of diseases.
One example of the complex role parasites can play is a hairworm that lives in grasshoppers in Japan and tends to lead its host to jump into water, where the grasshoppers become a major food source for rare fish. “In some subtle ways, parasites are puppeteers,” Carlson said.
The abstract of the study;
Parasite biodiversity faces extinction and redistribution in a changing climate
Colin J. Carlson, Kevin R. Burgio, Eric R. Dougherty, Anna J. Phillips, Veronica M. Bueno, Christopher F. Clements, Giovanni Castaldo, Tad A. Dallas, Carrie A. Cizauskas, Graeme S. Cumming, Jorge Doña, Nyeema C. Harris, Roger Jovani, Sergey Mironov, Oliver C. Muellerklein, Heather C. Proctor and Wayne M. Getz
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.
Sadly I see no long term drop in the number of parasites to support this claim. Many Parasites tend to have rapid life cycles. Many of them also have wide ranges, spanning significant variations in climate. This suggests a substantial ability to adapt to any plausible amount of climate change we are likely to experience in the foreseeable future.