The introduction of genetically engineered crops (and related herbicide use) has taken a lot of heat over the past 25 years as being the source of declining monarch butterflies and milkweed populations. But new research published in the Proceedings of the National Academy of Sciences indicates that the population declines began around 1950, decades before “GMO” was even a thing.
More concerning is that it’s not clear to the researchers what sparked the declines, and thus we as a society may still be failing to address the real cause of the problem.
“Whatever factors caused milkweed and monarch declines prior to the introduction of GM crops may still be at play, and, hence, laying the blame so heavily on GM crops is neither parsimonious nor well supported by data,” the research noted.
Joshua Puzey, a College of William & Mary researcher, and his colleagues gathered digitized museum and herbaria records for 1,191 monarch specimens and 39,510 milkweed specimens collected from 1900 to 2016. Analysis of long-term trends revealed that both monarchs and milkweeds suffered a two-fold decline between approximately 1950 and 2016. Moreover, the abundance of the common milkweed, the primary host plant of monarchs, was negatively associated with the number of farms, which declined between 1950 and 2006 as smaller farms consolidated.
The findings suggest that a decrease in the number of farms may predict common milkweed trends more strongly than herbicide-resistant crops, which were not introduced until 1996.
While this doesn’t entirely dismiss modern agricultural practices as a possible contributing factor, it clearly states that the intense focus on and vilification of herbicide-tolerant crops is misplaced.