Monarch butterfly populations have been declining since the 1990s, and several studies have linked this to the proliferation of crops genetically engineered to tolerate the glyphosate-based herbicide Roundup.
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While the correlation between monarch declines and herbicides is stark, consensus among scientists is not universal. Factors such as climate change, deaths during migration and loss of overwintering habitat in Mexico have also been implicated. One recent study used museum collections to show monarch numbers began falling decades before glyphosate-based herbicides were even invented—but it is drawing criticism from some ecologists who study these butterflies.
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[In February] a study in Proceedings of the National Academy of Sciences….digitized museum records of milkweed and monarch specimens dating back to 1900 to assess population trends. The analysis indicated milkweed and monarchs both started declining in the 1950s—well before the advent of glyphosate.…
Tyson Wepprich, an entomologist at Oregon State University, was apparently the first to identify what he says is a flaw in the study….Wepprich contends they missed the fact that Lepidoptera collection methods changed over the last century—in a way that he says favors the collection of moths.
Read full, original article: Study on Weed-Killers and Monarch Butterflies Spurs Ecological Flap
