From Monarch Watch
The decline has been attributed to three main factors: 1) the widespread adoption of herbicide tolerant corn and soybean varieties by North American farmers which has had the effect of eliminating milkweeds (the host plants for monarchs) within the crop fields; 2) the ethanol mandate passed by Congress in 2007 that increased the price of corn and soybeans which in turn led to the conversion of grasslands to crops thus elimination of the milkweeds that occurred in these areas; and 3) three consecutive years during which the reproductive success of the summer breeding population was limited by unfavorable weather conditions. The loss of habitat, i.e. milkweed and nectar plants that sustain the monarch population, is massive yet can be mitigated. In the paragraphs below I will briefly outline a vision and goals for monarch recovery and will describe the infrastructure, resources and partnerships needed to implement this recovery plan.
http://monarchwatch.org/blog/
