by Staff Writers
Saturday, March 17, 2012
Herbicides a Surprise Threat to Butterfly Populations
We have a fundamental problem with all forms of the chemical strategy to both weed and insect control. Somehow we have deluded ourselves into thinking that the products are generally benign and now we have a steady stream of long term studies showing that this is not true at all.
The first line of defense is to promote living refugia everywhere the land is not cropable in the first instance and possibly to plant tree lines even in fields. Then at least, we have ample places for the stocks to be nurtured.
I think that the transition back to an organic protocol to farming has only begun and will gather momentum over the next two generations upon which most of these issues will simply disappear. The present problem is to protect what we have as well as we can.
Commonly used herbicides seen as threat to endangered butterflies
by Staff Writers
toxicologist has found that three commonly used herbicides can dramatically
reduce butterfly populations.
The research was aimed at possible effects on the Lange's metalmark, an
endangered species in northern California, but it has implications for other
at-risk and endangered butterflies wherever herbicides are used, says John
Stark, an ecotoxicologist and director of the WSU Puyallup Research and
Extension Center. Washington
Stark and his colleagues tested triclopyr, sethoxydim and imazapyr on butterflylarvae at the request of the U.S. Fish and Wildlife Service, which uses the herbicides to maintain habitat for the Lange's metalmark in its last habitat, the Antioch Dunes National Wildlife Refuge in northern California. The researchers used the Behr's metalmark as a proxy for the Lange's metalmark, whose endangered status precludes using it for tests.
The researchers found adult numbers of the Behr's metalmark butterfly dropped by one-fourth to more than one-third when their larvae were exposed to regularly applied rates of the herbicides.
In a small population of endangered animals, says Stark, "any kind of reduction like that is going to be a problem."
While the dunes may have harbored 25,000 Lange's metalmarks 50 to 100 years ago, damage to the dunes reduced the population to 5,000 by 1972 and as low as 45 in 2006.
Key to the butterfly's survival is the naked stem buckwheat plant, which is easily overgrown by the non-native plants ripgut brome, vetch and yellow starthistle.
Refuge managers have tried to weed by hand but the process risks disturbing the buckwheat plants and butterfly eggs and larvae. And when the refuge managers started spraying the plants with herbicides, they noticed the butterfly populations were dropping even more, says Stark.
The study, funded by the Fish and Wildlife Service and published in the journal Environmental Pollution, is one of the first to document the effects of herbicides on butterflies. Several studies have shown herbicides can adversely affect animal life, even though they are designed to kill plants.
Each of the three herbicides in the Stark study operate differently, leading the researchers to think butterflies are being affected by inert ingredients or an effect on the butterflies' food source.