Aggressive non-native weeds are a problem and will continue to be a problem for the butterfly as well as many other native species of both plants and animals. As pointed out in the Federal Register, unfortunately efforts to control exotic plants with herbicides may also pose a threat to the checkerspot. The bottom line is that these weeds are a difficult problem. But there is no evidence yet that weeds have had any effect on the butterfly populations. What is even more ridiculous is that global warming is being given as a reason to list the butterfly as endangered.
Some scientists see global warming coming, some say maybe.
Give me a break. Livestock overgrazing was given as a problem by the environmental group. But as pointed out in the Federal Register, some areas used by the butterfly have been grazed by wildlife and domestic livestock for a number of years. Here is the corker. Potential over-collecting of the butterfly is given as threat to the butterfly.