The Mission Blue butterfly is a federal endangered species which existed historically on Twin Peaks in San Francisco. San Francisco’s Natural Areas Program has been trying to reintroduce the Mission Blue to Twin Peaks for several years, so far with limited success. Visit the Save Sutro website for a detailed description of these efforts which began in 2009.
The “Recovery Action Plan for the Mission Blue Butterfly at Twin Peaks Natural Area” acknowledges the difficulty of this undertaking. It cites a study of 226 attempts to reintroduce butterflies where they have been extirpated (locally extinct). These attempts lasted an average of 15 years. Only 29 of the attempts were ultimately successful. So what are the odds of success on Twin Peaks?
Identified obstacles to success
The federal Endangered Species Act requires that a recovery plan be written for each endangered species. These recovery plans are a valuable source of information about each endangered species, the factors that resulted in their endangered status, and the plans to promote the recovery of the population. From the recovery plan for the Mission Blue, we learn of several issues that make its reintroduction problematic at best:
- The Mission Blue is dependent upon just 3 species of lupine for its development. Two of these exist on Twin Peaks, but the predominant species is infected with a fungal pathogen which flares up during warmer, wetter weather. The small population of Mission Blues on Twin Peaks crashed in 1998 when the fungal pathogen killed many of the lupines.
- The lupine is crowded out by scrub species if natural disturbances such as fire do not prevent natural succession from grassland to scrub such as native coyote brush.
- Non-native species of plants are also competitors of the native lupines and their growth is encouraged by higher levels of nitrogen in the soil found in urban environments as a result of the burning of fossil fuels.
The Natural Areas Program cannot control these factors:
- There is no known cure for the fungal pathogen that is killing lupine. In wetter years, it is likely to kill some of the lupine on Twin Peaks again, as it has in the past.
- The Draft Environmental Impact Report for the Natural Areas Programs says that prescribed burns will not be conducted in the “natural areas.” Prescribed burns are conducted by the State parks department periodically on San Bruno Mountain, where a viable population of Mission Blue butterflies exists. This method of preventing natural succession to scrub in order to maintain a population of the butterfly’s host plant will not be an option on Twin Peaks.
- We should probably assume that existing automobile traffic in San Francisco will continue to contribute to nitrogen in the soil for the foreseeable future. Higher levels of nitrogen will promote the growth of the non-native vegetation that competes with the native lupine upon which the Mission Blue depends.
Unidentified obstacles to success
In addition to the issues that have been identified by federal and local recovery plans, the Natural Areas Program has introduced a new threat to the Mission Blue. Herbicides are being used on Twin Peaks to control non-native vegetation. Twin Peaks was sprayed with herbicides 16 times in 2010 and 19 times in 2011. Are these herbicides a factor in the limited reproductive success of the Mission Blues that have been reintroduced to Twin Peaks?
A recently published study reports that the reproductive success of the Behr’s metalmark butterfly was significantly reduced (24-36%) by herbicides used to control non-native vegetation. Two of those pesticides are used on Twin Peaks, imazapyr and triclopyr. Triclopyr was used most often on Twin Peaks in 2010 and imazapyr in 2011.
The study does not explain how this harm occurs. It observes that the three herbicides that were studied work in different ways. It therefore speculates that the harm to the butterfly larva may be from the inactive ingredients of the pesticides which they have in common, or that the harm comes to the larva from the plant which is altered in some way by the herbicide application. Either theory is potentially applicable to the herbicides used on Twin Peaks and consequently harmful to the Mission Blue.
Native plant advocates would like us to believe that the herbicides used to eradicate non-native plants are not harmful to animals, including humans. In fact, they don’t know that. The truth is that no one knows if herbicides are harmful to animals because there is almost no research that would answer this question. The tests required by law by the Environmental Protection Agency to put new chemicals on the market are very limited. The honeybee is the only insect on which the EPA is required to test chemicals before they are put on the market. No tests are required for butterflies or any other insect.
US Fish & Wildlife funded the research on the Behr’s metalmark butterfly which suggests that herbicides are harmful to butterflies. US Fish & Wildlife is also the co-sponsor and co-funder of the reintroduction of the Mission Blue butterfly on Twin Peaks. Will US Fish & Wildlife advise the Natural Areas Program that herbicide use on Twin Peaks should be stopped?
In a more perfect world we would have the wisdom to stop using pesticides until we had some scientific evidence that they are not harmful to us and the animals with which we share the planet.