Shrinking Forests Drive Mosquitoes to Bite Humans
The study finds that mosquitoes will turn to humans if their main food source, animals, disappears. (Lauren Bishop/CDC via AP)
Mosquitoes may be developing a greater appetite for human blood—not by choice, but by circumstance. New research from Brazil suggests that widespread deforestation is pushing mosquitoes to change their feeding habits as wildlife disappears, according to Popular Science. Instead of feeding on animals, mosquitoes in affected areas are increasingly turning to humans.
This shift is more than just uncomfortable. It could significantly raise the risk of spreading mosquito-borne illnesses such as dengue, Zika, and yellow fever.
The study, published in the journal Frontiers, examined two regions in Brazil’s Rio de Janeiro state that were once part of the Atlantic Forest. Due to logging and development, that forest has been reduced to about 29% of its original size. In areas that were previously uninhabited by people, researchers detected human blood in nine different mosquito species.
“When the animals that mosquitoes usually feed on disappear, mosquitoes can switch to humans,” Laura Harrington, an entomology professor at Cornell University, told ABC News. Study co-author Sergio Lisboa Machado of the Federal University of Rio de Janeiro described mosquitoes as “opportunists.” Because they typically do not travel far, they feed on whatever host is closest rather than expending energy searching for wildlife.
Earlier research has already shown that deforestation is linked to rising mosquito populations and higher rates of mosquito-borne disease. Disturbed environments tend to favor tough, adaptable mosquito species that thrive near human settlements. At the same time, the loss of wildlife removes natural “buffer” species that help limit disease spread, leaving people as the primary blood source.
Out of roughly 3,500 mosquito species worldwide, Harrington notes that only a small fraction strongly prefer humans. However, changes to the environment can quickly alter that balance. “When we change the landscape, we can change mosquito feeding behavior—and sometimes that shift moves directly toward humans,” she said.
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