This week's Science Friday had a segment with Lincoln Brower, an entomologist'
"In previous years we had seventeen sites with colonies, this year eight of those sites had zero butterflies, and the rest of them had very few butterflies. Only one of the colonies had significant numbers. My worry is that they are winking out one by one and they may not be able to recover"There are several reasons for this, among them that the Oyamel forest is being thinned which exposes the area under the canopy and makes it harder for the butterflies to shelter from winter frost in the high forest. Monarchs have an absolutely crazy life cycle. Simplified, overwintering butterflies in Mexico (there are also populations in California, and they ain't in good shape judging from the last few times Eli was on the Monterey Peninsula) leave Mexico in late March and head for Texas, where they feed on milkweed and create a new generation. The new generation is short lived, and starts the migration north to the Great Lakes region and the east coast. They, in turn, lead to two other short lived generation, with the fourth and final one being the one that migrates back to Oyamel and overwinters. You can follow this on Journey North, a science activity for young and old. Another great site to learn more is Monarch Watch.
Monarch larvae are fussy eaters, depending on milkweed the way that pandas depend on bamboo. It is the only thing that they feed on in that stage of their lives. This has made them indirectly vulnerable to GMOs. The introduction of Roundup Ready crops has lead to broadcast spreading of Roundup, which kills everything EXCEPT the Roundup Ready crops, including the milkweed (and also nectar yielding plants which does nasty things for pollinators). This breaks the Monarch's lifecycle.
Roundup Ready GMOs are creating food deserts for Monarchs and many other species. Not only those that enrich our lives, but others that we depend upon.