When Forest Disappears, But Mosquitoes don’t!

Deforestation doesn’t just remove trees — it removes our biological shield

With increasing deforestation, studies showed that mosquitoes in the Atlantic Forest are showing a preference for human hosts over potential vertebrate hosts in the forests, increasing the susceptibility of mosquito-borne disease transmission. When the rich Atlantic Forest was reduced to one-third of its initial area, a disturbing trend was observed by the scientists – the native mosquito species are now shifting from other potential vertebrate hosts to humans as preferred hosts.

Over 1,700 mosquitoes were captured, and blood meals trapped within engorged females were analysed using DNA barcoding to identify the victims of these silent killers. Sequencing the Cytochrome c Oxidase I (COI) gene (mitochondrial biological barcode) helped scientists note the shift in the hosts of these mosquitoes, who once fed on forest wildlife but now haunt the human population.

This finding is a harsh molecular confirmation of the dilution effect hypothesis. According to this hypothesis, a high level of biodiversity serves as a biological barrier against disease. In a biodiverse environment, the disease is "diluted" among a very large number of species, most of which are "dead-end hosts" and cannot transmit the virus to mosquitoes, thus preventing the chain of transmission. However, with the depletion in their natural hosts and expanding human settlements, human beings become the most accessible host – the shift from zoophilic to anthropophilic preference of mosquitoes.

Moreover, the establishment of “edge habitats", the irregular boundary between the fragmented forests and human front yards, accelerates the zoonotic spillover. This constant closeness establishes a link for pathogens that live in the forests to adapt to the human physiology, effectively turning a balanced ecosystem into a hot zone for amplification of pathogens. In the end, we are not merely losing trees; we are losing the biological shields that keep the Zika and yellow fever viruses locked away in the forest.

This highlights yet another reason to work on forest conservation while also equipping ourselves for the potential increased susceptibility to mosquito-borne disease.

References:

https://www.frontiersin.org/news/2026/01/15/mosquitoes-human-blood-biodiversity-loss