Monarch butterflies and their principal host plant, the milkweed, have been declining in abundance even before GM crops were planted. This was the result of an extensive study conducted by Jack Boyle, a Mellon Postdoctoral Fellow of Environmental Science and Policy at College of William & Mary.
Boyle and team’s study is published in the Proceedings of the National Academy of Sciences of the USA (PNAS). The researchers gathered the digital records from museums and herbaria throughout North America and analysed the relative abundance of both monarchs and milkweeds for over a century (1900-2016). The decline of these two species commenced in 1950, the study noted.