Researchers sound alarm over increased number of disease-carrying insects: 'This is a major concern'

If you jump every time you see a spider, news that their numbers are decreasing in a particular area may be a relief — but the decrease in numbers has consequences. 

According to the Indian Institute of Science for Phys.org, a new study in the Himalayas shows that areas with domestic grazers are seeing a decline in spiders and an increase in "grasshoppers and disease carriers like ticks and mites." 

What's happening?

The 15-year study, published in Ecological Applications, examined how replacing wild herbivores like yak and ibex with domestic cattle like sheep in Spiti Valley affects arthropod numbers. 

"The team tracked the presence of more than 25,000 arthropods spanning 88 different taxa, including spiders, ticks, mites, bees, wasps, and grasshoppers, in fenced plots grazed separately by domestic and wild herbivores," per Phys.org. 

It analyzed the soil and vegetation. Arthropods rely on the vegetation as a source of food and habitat.

The study found that the number of spiders, mites, and ticks was influenced by whether domestic or wild grazers were on the land. Spider numbers decreased while the populations of mites and ticks drastically increased. 

It's unclear why spiders are being reduced in number. One theory is they are losing a food source because plants are changing.

Why are arthropod numbers changing concerning?

"One of the most surprising observations was the massive difference in tick and mite abundance between native grazers and livestock," said Pronoy Baidya, the study's co-first author. 

The study authors also explained that an estimated 80% of global cattle have ticks that threaten human and animal health. 

Baidya added: "This is a major concern for zoonotic diseases."

Should we be actively working to kill invasive species? Absolutely It depends on the species I don't know No — leave nature alone Click your choice to see results and speak your mind.

According to the World Health Organization, "vector-borne diseases account for more than 17% of all infectious diseases, causing more than 700,000 deaths annually." They include malaria, dengue fever, West Nile fever, yellow fever, Zika virus fever, chikungunya fever, and tick-borne encephalitis. 

Another concern about the decrease in spider numbers is the change in the ecosystem. 

"Spiders are predators; their ecological roles are similar to wolves, lions, and tigers. A low abundance of spiders can release grasshoppers from predator control," said Sumanta Bagchi, another author of the paper. 

Removing predators from an area can have drastic changes, as was the case in Yellowstone National Park when wolves were eradicated. 

According to National Geographic, without the wolves, elk overgrazed, causing a domino effect. Rabbit and mouse populations declined because they had nowhere to hide from predators. 

What's being done about arthropod numbers?

The researchers suggest rewilding "native herbivores and improved surveillance of vector-borne disease risks in areas where animals and humans coexist." 

The research team also calls for "effective conservation policies" to combat the issue. You can use your voice to speak to your representatives about enacting policies that will tackle the problem.

Join our free newsletter for good news and useful tips, and don't miss this cool list of easy ways to help yourself while helping the planet.