Parasites are unloved creatures, their very mention sends a chill down many spines. Creatures such as lice, bed bugs, and ringworm can cause great harm, much discomfort, and much suffering to their human hosts, on whom they depend for their survival.
However, most parasites are harmless to people, as only 4% of them pose a threat to us. Not only that, but parasitic creatures, from plants to animals, fulfill vital ecological functions, which is why they should feature in global conservation plans, argues a team of scientists from the United States.
"Parasites are an incredibly diverse group of species, but as a society, we do not recognize this biological diversity as valuable,"Explain Chelsea Wood, who researches the ecology of parasites at the University of Washington and is the author of aArticle in the magazineBiological Conservation on the need to save parasites from extinction globally. "We are losing parasites and the functions they fulfill without even recognizing it."
Many of us might think of parasitic animals as unworthy of protection, yet they are among the most diverse and ecologically important animals on Earth, scientists note. Being as diverse as they are, parasites range from parasitic plants like mistletoes to less lovable creatures like isopods that live in water and feed on fish tongues, thus occupying a very wide spectrum of ecological niches. .
However, they are among the least protected species that rarely or never appear in wildlife or ecosystem conservation efforts.
“For decades, ecologists have been calling for research to understand the important ecological role of parasites and, increasingly, to protect as many species as possible from extinction. However, most conservationists still work within priority funding and effort systems that exclude or ignore parasites, or treat them as an obstacle to overcome, ”write the researchers, whose work is supported by National Science Foundation of the United States.
Scientists have set 12 goals to advance the cause of parasite biodiversity conservation, including more research and better conservation management. Importantly, they argue that half of the world's parasites should be taxonomically described and named within the next decade so that these creatures and their ecological roles can be better understood.
"If species don't have names, we can't save them," observes Colin Carlson, assistant professor at Georgetown University. “We have accepted that for decades in most animals and plants, but scientists have only discovered a fraction of a percentage of all parasites on the planet. Those are the last frontiers: the deep sea, deep space and the world that lives inside all the species on Earth ”.
However, the scientists emphasize that their conservation scheme does not extend to parasites that infect humans and domestic animals because they must be controlled. Nor is it a fact, they stress, that parasites in nature are universally at risk of extinction. "We shouldn't take it for granted that all parasites are going extinct or about to cause a major outbreak," emphasizes Wood.
Many parasites are very complex, he explains. Some of them require multiple hosts throughout their lives, which may mean that they first infect fish or amphibians but end up being transmitted to birds to reproduce. To do this, they can manipulate the behavior or even the anatomy of their first fish or amphibian host to ensure that they become more susceptible to being eaten by birds, so that the parasite can end up in its required new host.
Wood and his colleagues designed an experiment around 16 ponds in the East Bay region of central California to see how local parasites responded to changes in their environment. In eight of the ponds, the scientists installed structures such as birdhouses, floating perches and mallard decoys to attract more birds to the sites. In the remaining eight ponds they made no changes.
After a period of two years, the researchers analyzed the biodiversity of parasites in each of the 16 ponds. What they found was that some parasites decreased in number when more birds were around, while other parasites increased overall. In other words, different species of parasites will respond differently to changes in their environment, which should come as no surprise.
Whether a drastically changed climate and environment in the next few decades will lead to parasite explosion or extinction will depend on several variables, but "we must anticipate both trajectories," Wood emphasizes. "The trick now is to find out which traits will predict which parasites will decrease and which will increase in response to the loss of biodiversity."