[Pollinator] neonicotinoid use and butterfly population decline

[David Inouye]

    Controversial pesticides threaten not just bees, but butterflies,
    too August 17, 2016


    Conservation This Week
    <http://conservationmagazine.org/conservation-science-news/>

Most of the furor surrounding neonicotinoids, the world’s most 
widely-used pesticides, focuses on the harms they cause to bees. Yet 
these chemicals may also pose a threat—presently little-appreciated but 
possibly grave—to butterflies.

In a study published in the journal /Biology Letters/ 
<http://dx.doi.org/10.1098/rsbl.2016.0475>, researchers led by biologist 
Matthew Forister of the University of Nevada tracked butterfly 
populations across four decades in three Northern California counties. 
Butterflies there face many challenges, including climate change, 
drought, and habitat loss to agriculture and urban sprawl. Yet even with 
those factors accounted for, neonicotinoids seem to pose a unique 
threat: the researchers found that declines in butterfly health and 
reproductive success accelerated dramatically after the pesticides 
entered widespread use in the mid-1990s.

There are caveats to the study, stress the researchers. “The evidence is 
correlational,” cautions study co-author Art Shapiro, an ecologist at 
the University of California, Davis, who started monitoring the region’s 
butterflies in 1972. “That’s not the same thing as proving causation.”

If not definitive, though, the findings do dovetail with similar results 
from a long-term, large-scale study of butterfly populations in Great 
Britain. They also fit with what’s known about the toxicity of 
neonicotinoids to insects and the chemicals’ ubiquitous environmental 
presence due to runoff from agricultural fields and urban landscaping. 
There might not be fire, but there’s certainly a lot of smoke.

Public concern about neonicotinoids and bees has prompted the 
Environmental Protection Agency to review their safety, and some 
municipalities have restricted their use. While awaiting further 
research and regulation, one wonders: what might become of a world with 
fewer butterflies?

“We don’t know,” says Shapiro. “For this area, at least, the sky has not 
fallen.” Then again, it’s only been an ecological eyeblink since the 
butterfly declines started. The effects may take many more decades to 
become obvious. Perhaps there would be fewer of the plants that 
butterflies pollinate, and fewer of the animals who feed on them. If 
nothing else, there would be a lot less beauty in the world. *—Brandon 
Keim | 17 August 2016*

*Source:* Forister et al. Increasing neonicotinoid use and the declining 
butterfly fauna of lowland California. /Biology Letters,/ 2016. doi: 
10.1098/rsbl.2016.0475


    Abstract

The butterfly fauna of lowland Northern California has exhibited a 
marked decline in recent years that previous studies have attributed in 
part to altered climatic conditions and changes in land use. Here, we 
ask if a shift in insecticide use towards neonicotinoids is associated 
with butterfly declines at four sites in the region that have been 
monitored for four decades. A negative association between butterfly 
populations and increasing neonicotinoid application is detectable while 
controlling for land use and other factors, and appears to be more 
severe for smaller-bodied species. These results suggest that 
neonicotinoids could influence non-target insect populations occurring 
in proximity to application locations, and highlights the need for 
mechanistic work to complement long-term observational data.


-- 
Dr. David W. Inouye
Professor Emeritus
Department of Biology
University of Maryland
College Park, MD 20742-4415
inouye at umd.edu

Principal Investigator
Rocky Mountain Biological Laboratory
PO Box 519
Crested Butte, CO 81224

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