Monarch butterfly and milkweed declines substantially predate the use of genetically modified crops
Abstract
The recent decline of the monarch butterfly has attracted a great deal of attention. One of the leading hypotheses blames genetically modified (GM) crops, ostensibly because of the impact of GM-related herbicide use on the monarch's food plants, milkweeds. Here, we use museum specimen records to chart monarch and milkweed occurrence over the past century (1900 to 2016), dating well before previous datasets begin (in 1993). We show that monarch and milkweed declines begin around 1950 and continue until the present day. 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.
- Publication:
-
Proceedings of the National Academy of Science
- Pub Date:
- February 2019
- DOI:
- 10.1073/pnas.1811437116
- Bibcode:
- 2019PNAS..116.3006B