Climate change carries new risk to isle birds, study finds

Global climate change could further imperil indigenous Hawaiian bird populations over the next century as rising temperatures and increased rainfall draw malaria-bearing mosquitoes into protected avian habitats, according to researchers at the U.S. Geological Survey and the University of Wisconsin-Madison.

The findings are included in a new study published in the current online edition of Global Change Biology.

Aware that avian malaria historically has been linked to bird extinctions, the team set out to explore how changing climates could affect the "bird-mosquito-disease system."

As the researchers noted, a single mosquito bite can transfer malaria parasites to a susceptible bird, resulting in a death rate as high as 90 percent. Thus, many threatened species of native bird survive only in disease-free refuges in high-elevation forests, the colder temperatures of which serve as a natural barrier to mosquitoes.

However, as temperatures rise and rainfall increases, mosquitos will be able to survive at higher elevations, allowing them to invade previously protected bird habitats.

"We knew that temperature had a significant effect on mosquitoes and malaria, but we were surprised that rainfall also played an important role," said scientist Michael Samuel of the USGS Wisconsin Cooperative Wildlife Research Unit. "Additional rainfall will favor mosquitoes as much as the temperature change."

According to the team, without "significant intervention," native bird communities will be substantially decreased starting at midcentury.

The researchers noted that land managers could help to prevent or minimize bird population declines by restoring and improving bird habitats, reducing mosquitoes on a large scale and controlling predators.