A new study (abstract below) has found that the monarch butterfly population in the US has “a substantial probability of quasi-extinction, from 11–57% over 20 years”.
The study repeats the well-documented fact that a major factor in the decline of the monarch is the adoption of herbicide-tolerant GM corn and soybeans. The herbicide spraying has killed off the monarch larvae’s only food, the milkweed plant.
Given the findings of the new study, it seems premature to give credence to a suggestion made in one article that the monarch population may be “on the rebound”.
As the article also states, while the population of monarchs who made their annual trip to Mexico this past December increased three-and-a-half times from the previous year, the totals are still far below those from two decades ago. And the rise may be a temporary blip caused by favourable weather conditions.