Butterflies in Danger: Routine Mosquito Sprays Harm More Than Thought

It's no secret that the world's pollinators have been having a rough time of things these past few decades. It's also no secret that pesticides - at least in part - are to blame, although some UK officials might disagree. Now new research has determined that sprays commonly used to control mosquito populations in the United States may also be having an adverse effect on common butterfly populations.

That's at least according to a suite of studies recently published in the journals Environmental Toxicology and Chemistry; Science of the Total Environment; and Chemosphere.

The studies contain detailed assessments of the abundance and diversity of butterfly populations in South Florida, where researchers spent five years observing common varieties including the white peacock butterfly, the atala hairstreak, and the common buckeye.

What they found was some compelling evidence that these insects were threatened by something locally, but it was important to note that natural influences also play their part. Florida is home to many parasitic species, for instance - a factor that is trapping and harming monarch butterflies that intended to simply stay for the winter. They are drawn in, however, by Floridian gardeners with good intentions, planting non-native tropical milkweed that unintentionally serve as ideal parasitic breeding grounds. You can read more about this conservation disaster here.

"Changes in butterfly populations that occur as a result of natural factors are difficult to control and manage," Gary Rand, director of the Ecotoxicology and Risk Assessment Lab at Florida International University, explained in a statement.

However, "human factors," he added, "like our use of insecticides, can certainly be monitored and managed more effectively."

Rand's lab specifically found that butterflies are being exposed to naled, permethrin and dichlorvos - insecticides sprayed locally for mosquito control - far more than is acceptable, as it was already known that these chemicals were toxic to many species past a certain concentration. (Scroll to read on...)

The Environmental Protection Agency (EPA) already lists the three insecticide varieties as highly toxic to aquatic organisms and honeybees, and it is bees standards which are used to control local spraying concentrations.

However, the researchers argue that with their wide wings, butterflies wind up filtering far higher concentrations of these chemicals from the air than bees do, attaining potentially toxic exposure. What's more, some species were found to be particularly vulnerable to naled as caterpillars when eating contaminated leaves.

"These results are based only on ingestion and single chemical doses," Rand added. "It doesn't include other typical exposure scenarios that may occur in the environment, where the organisms may be exposed via environmental drift and to multiple or continuous exposures."

This essentially means that even with results already showing potentially toxic levels in South Florida, the situation may be even worse.

So what's to be done? The good news is that all three of the aforementioned studies were funded by the US Fish and Wildlife Service, which is looking to be more proactive about the impact of insecticides on native pollinators. Last July, for instance, the service placed a permanent halt on all neonicotinoid spraying in US wildlife refuges, while slowly phasing out plants contaminated with the toxin. The work is expected to be completed by 2016.

And in the Florida Keys, officials are looking for new non-chemical ways to keep mosquito populations down - looking to preserve local pollinators while simultaneously addressing the threat of mosquito-borne illness.

However, one approach that has earned a lot of backing concerns the use of genetically modified mosquitoes - a revelation that has put many locals on edge. You can read more about that here.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

- follow Brian on Twitter @BS_ButNoBS