A commenter on this website, ‘Jonathan’, suggested that a good reason to destroy the Mount Sutro Cloud Forest would be to bring back habitat for endangered butterflies. Besides the Mission Blue Butterfly (for which there’s an attempted reintroduction on Twin Peaks) he suggested three others: The San Bruno Elfin, a tiny brown butterfly (pictured); the Callippe Silverspot; and the Bay Checkerspot. These are all butterfly subspecies found on nearby San Bruno mountain, which has some 2700 acres of preserved habitat. (A subspecies is what it sounds like: a division below the “species” level. Subspecies of animals or insects can often interbreed, but don’t usually because of geographic isolation.)
So we thought we’d look into it, (though we’d consider the destruction of this unique and beautiful forest a very high price to pay). The answer, as one might expect, is complicated.
According to a 2001 article by Sherri Graves and UC Davis’s Professor Art Shapiro, some 82 of California’s 236 butterfly species are already known to use introduced plants for feeding and/ or breeding. This can allow a species to expand its range or its breeding period, making it more successful. One example is the Anise Swallowtail, which now breeds on non-native fennel. Another is the Monarch butterfly, which uses the eucalyptus that has replaced all the other tall trees that were felled for lumber or land. [ETA: In a 2002 paper, Prof. Shapiro notes that around Davis – perhaps the most intensively studied butterfly habitat in the US – 29 of the 32 species breed at least partly on introduced plants. And 13 don’t seem to have a native host plant at all.]
Because insects have short life-cycles, they often can adapt to changed vegetation, and more may be in the process. For instance, some butterflies may lay their eggs on plants that poison their larvae. If there’s enough genetic variation in the population, a few larvae might actually survive. If they pass on their immunity to their offspring, they have another plant to use.
So what about these endangered butterflies? It turns out that at least at present, they all breed on very few plant species. Their caterpillars are picky. (We can also speculate that perhaps there’s not be enough variation within their diminished populations for them to adapt to other plants, though of course we don’t know this.) The Mission Blue breeds on a few species of lupine. The San Bruno Elfin needs broadleaf stone-crop. And the Calippe Silverspot (Speyeria callippe callippe, an endangered subspecies that shades into Callippe Comstocki to the south, and Callipe Liliana up in Marin) uses the yellow pansy as baby food.
Then there are the ants as nurses. Some species (the Mission Blue and the Callippe Silverspot, don’t know about the others [ETA: Also true of the San Bruno Elfin]) need native ant species to nurture their caterpillars. The ants, attracted by “honeydew” – a sugary caterpillar pee, protect caterpillars from enemies. Even on San Bruno Mountain, the relatively warm eastern side has native ant populations; the windy foggy western side has mainly Argentine ants. Mount Sutro, which is windy and foggy on all sides (because of the way the fog belt works) is unlikely to be a warm safe place for ants. [ETA: Argentine ants do apparently tend caterpillars, though it’s not known how effectively they defend them.]
So restoring butterfly habitat isn’t as simple as “if you plant it, they will come.” According to a 2007 report on San Bruno mountain – where the battle is to preserve habitat from housing development – there have been no instances of successful butterfly habitat restoration in 25 years: “The process of destruction, mitigation, and restoration does not address the site specific ecology of butterfly species, and the complexity of these grassland systems. It is entirely without scientific merit. The survival of these butterflies is not as simple as the farming of host plants, or the mass rearing of larvae (Matoon et al 1971). To replicate the system would require its associated group of organisms to all be present. To the best of my knowledge, no new Mission Blue nor Callippe Silverspot areas have been established by humans in the past twenty five years…”
Finally: These are grassland species, growing in flammable spaces. Pansies apparently need occasional fires to burn off competing plants. The lupines grow best in disturbed ground, where it’s burned or there’s been a landslide. Fire may be part of the ecological cycle that keeps their host plants healthy.
San Bruno Mountain’s had a bunch of fires. A prescribed burn in 2003 got out of control and burned over 70 acres. In August 2006, a 50-acre fire was put out with helicopter assistance. May 2008, a 7-acre grass fire was contained after it went to three alarms. Then in June 2008, a five-alarm fire burned 300 acres and threatened homes.
It’s bad enough in San Bruno, but that has 3,000 acres of open space. Mount Sutro Forest is 80 acres, surrounded by homes and a hospital. Converting it to a fire-prone ecology is a bad idea.
This post only lists the 4 of the 5 butterflies I listed as most endangered (skipping the Myrtle Silverspot), and you only dispute the site’s suitability for two of those species (one of which was previously recorded as having a sustained population on Twin Peaks and has already survived at least one reproductive cycle after its reintroduction there last year).
But there were actually 20 butterfly species that used to live in San Francisco and are now gone from the region, and another dozen at least that are extremely rare there. It can be complicated, as you say, but don’t you accept that a native restoration of habitat on Mount Sutro would likely allow suitable habitat to grow for a fair number of those butterflies that are currently absent from the San Francisco experience?
It’s true we didn’t cover the Myrtle Silverspot – didn’t actually find enough information to make a call one way or the other. Also, its main population is at Pt Reyes, and its unclear if the conditions there echo the conditions in San Francisco.
But why should Mount Sutro Forest be managed for subspecies of butterflies? Why not leave it as a Cloud Forest and devote the resources to managing areas that are already grasslands like the Marin Headlands, and which have much more acreage?
Only 100 years ago, nearly a quarter of California’s butterfly species could be found on the San Francisco Peninsula. Now only 36 of those 56 species are left, and many of the remaining ones are in a lot of danger. North of San Bruno Mountain, there simply aren’t many places left where endangered butterflies could even be established anymore. We’re basically talking about Twin Peaks, Mt. Sutro, Golden Gate Park, the Presidio, and Lobos Point. Due to individual habitat requirements, especially those involving hills, it’s quite likely that Twin Peaks/Mt. Sutro is the only locale or one of only two locals in San Francisco where many of those species would be able to survive.
[Webmaster: San Francisco is a city – these are all small patches of habitat. But those that survive in San Francisco also seem to survive north of the city, in the Marin Headlands and further north. Considering what a populated place the Bay Area is, a lot of land has been kept open. Neither Twin Peaks nor Mt Sutro are ideal, but at least Twin Peaks is already grass/shrubland. We think it’s overly optimistic to assume that endangered butterflies could be established here. It would take a huge input of resources, and have a low probability of success.]
We could just give up on San Francisco’s native wildlife and say “Well, I guess we killed them all, too bad”, but I think that would be sad.
[Webmaster: We understand the emotional aspect of it; we feel similarly about the Cloud Forest. “Used to have a Cloud Forest here, chopped it all down for the butterflies, but it didn’t take… too bad. We’ll find something else to do with a nice open piece of land in the heart of the city.”]
And remember, this isn’t just about butterflies, butterflies just happen to be the best example. The same argument also covers endangered and rare plants, other arthropods, reptiles, and amphibians that are either gone or close to gone from San Francisco, and possibly several mammals and birds as well.
[Webmaster: Sure, but again – this is a City. Most of the land is covered with buildings and roads and other appurtenances of urban life. We all love having natural spaces in the city, or we wouldn’t fight for the Forest. Realistically, though, there’s no way to bring it all back in an urban environment. Which brings the argument full circle to where this started out on the LA Creeks blog – acknowledging the urban environment is important.]
It’s true that most of these species are still able to hang on outside of San Francisco, though a number of them are having a very difficult time hanging on. I still think that being able to have native populations within San Francisco is important for three reasons. First of all, geographic-specific conditions may make Mt. Sutro/Twin Peaks more ideal than these outside locations. That’s why three of the San Francisco natives are already extinct and a few others are barely hanging on – sites outside of San Francisco just don’t fit their habitat/climate requirements. [Webmaster: Could you cite your sources for that? It doesn’t agree with what we read. In fact, even the Mission Blue was originally found in a lower part of the city, which is now covered in housing. There’s no evidence that Twin Peaks or Mount Sutro are ideal habitat, just that they remain.]
Second of all, establishing multiple populations in multiple areas gives the species a better chance of survival. One catastrophic event at a site (like a massive wildfire encompassing San Bruno Mountain or a devastating disease spreading across the Marin Highlands) could wipe out an entire population, so having other populations established provides a safety net. [Webmaster: The intent is to establish and nurture meta-populations; the most cost-effective way to do that is to protect and extend existing populations rather than initiate resource-intensive projects in limited spaces.]
Finally, I find value in being able to still have these native animals in the San Francisco habitats where they once lived. It would be sad for me if people from San Francisco had to leave to other places to see the animals that once called the peninsula home. [Webmaster: San Francisco is 47 square miles. People leave to see most things. This is more than balanced, of course, by people coming in to see San Francisco. We’d suggest that on a foggy day – of which we have many – this Cloud Forest may be the most beautiful place in the city. If it were gone, there’d be no place to see such a forest, inside the city or out of it. Maybe in Tasmania.]
San Francisco was a peninsula first. Unfortunately, most of that peninsula was converted into a sprawling city. But to just say “it’s a city” now and to forget about the unique wildlife and habitats that did (or just barely still do) occupy it is to have an extremely shortsighted mindset.
And yes, some of those species do live in Marin….and some don’t. For instance, just out of the five endangered species I mentioned, the Bay Checkerspot (probably a good candidate for Sutro/Twin Peaks) and the Callippe Silverspot (probably would have a more difficult time) both are not found on Marin at all, and I’m not sure that the San Bruno Elfin is either. Plus, as I said, there is the benefit of having these species on the peninsula itself and the benefit of having multiple different reproducing populations.
As far as many species of San Francisco’s butterflies needing particular contours of hills to survive, you can look at the following sources. In some cases they need the wet sides, in some cases the dry sides, in come cases the non-windy side, in some cases they need varying contours to take advantage of different conditions at different times, and in some cases they congregate towards the ridges. They make it clear that regular lowland is not what they need:
Click to access 07-4060.pdf
Some other select information to augment the post. The primary source you used is a non-reviewed advocacy paper by a single biologist that was written to push a particular position (that native habitat needs to be saved because it is difficult to restore). This is certainly a limited viewpoint. Here are some important facts not covered in the article.
Callipe Silverspot Butterflies do seem especially adapted to survive periodic burns. However, that does not mean that they cannot survive areas that do not burn. They previously survived on Twin Peaks, and currently survive in a city park in Alameda County that burns much less frequently than San Bruno Mountain. And the Mission Blue Butterfly currently survives in several spots where burns are very rare, including locales within Fort Baker and the city of San Mateo. The population on Twin Peaks survived in numbers from at least 1979 through 2001. (I would suggest that the extremely small habitat size made it much more vulnerable to local extinction events, showing the potential benefit of an increase in the available habitat by a factor of 4 with the addition of a native Mt. Sutro.)
Ant-caterpillar interactions are a helpful boost to the development of Mission Blue butterfly larvae, but they are not a necessary part. The larvae can develop and mature without help from native ants.
Finally, I just want to point out that you mention that 82 of California’s 236 butterfly species use introduced plants for feeding and/or breeding. First off, 236 of 236 use native plants for feeding AND breeding, showing the vast superiority of native habitat for butterflies. Second, I’m sure you know from the research you’ve already done that breeding and larval development is the limiting factor, not feeding. A good number of those 82 species may be able to feed off a few invasive plants, but will still die out unless they have native plants to breed on. How many of San Francisco’s 56 butterfly species can feed AND breed in Mt. Sutro’s eucalyptus forest? How many more could make it in an equal area of native habitat?
Could you provide the references/ cites for your facts?
Burning is a way of favoring the viola pedunculata (yellow pansy) used by the Callippe Silverspot and the lupines for the Mission Blue. If they can be preserved in other ways (say by manual weeding of competitors) then fire isn’t actually needed. But in any larger terrain than a park or garden, this becomes tough. (This is why Roundup and Garlon are used on Twin Peaks.) It doesn’t help that the larvae are very herbicide-sensitive, or that the eggs are laid amid the dead plants.
The point though isn’t so much whether fires are necessary – it’s that the grassland habitat is fire-prone. Fort Baker did actually have fires, which in fact, inspired the prescribed burns planned for the Marine Headlands this fall.
Ants fight parasitism which can be a major cause of death among larvae. Even with ant-minders, there’s quite a high rate of parasitism according to USFWS information. Butterfly reproduction is a numbers game; without the ants, reproductive success rates could fall so the population doesn’t replace itself.
Restoration is very uncertain – even with ideal terrain where a population is known to exist, it takes substantial effort to even preserve what’s there. The report we cited was an effort to save an existing habitat. Even if butterfly conservation were your highest priority, would converting a forest be the best use of resources?
I have my own request for cites:
“The point though isn’t so much whether fires are necessary – it’s that the grassland habitat is fire-prone. ”
Comparing like to like, do you have any evidence that native habitat on Mt. Sutro would be more fire-prone than the current situation, or that such a fire would be more dangerous in the native habitat than it would be in the eucalyptus/ivy/blackberry forest? [Webmaster: At present it’s a very damp Cloud Forest, and so not fire-prone. As grassland, it would be significantly more flammable.]
If the closest example we have is Twin Peaks, has Twin Peaks been more fire-prone in a significant and dangerous way? [Webmaster: The advantage of Twin Peaks is that the roads that girdle it act as wide fire-breaks. Or we hope so, anyway. SF Library has a picture of a 1943 grass fire there, but at that time there would have been far fewer houses around it and on its lower slopes.]
“Butterfly reproduction is a numbers game; without the ants, reproductive success rates could fall so the population doesn’t replace itself.”
Do you have any evidence that a lack of ants, or a replacement of native ants with Argentine ants, actually causes this to happen? [Webmaster: Don’t know if anyone’s done the research about Argentine ants and whether they would guard or eat the larvae. But friendly ants apparently help; a Wikipedia entry on lycaenid butterflies quotes an article from Oecologia: “survival rates of G. lygdymus larvae declined 85-90% when ant partners were excluded.” (A.M. Fraser, A.H. Axen, and N.E. Pierce, “Assessing the Quality of Different Ant Species as Partners of a Myrmecophilous Butterfly,” Oecologia, vol. 129, Nov. 2001, pp. 452-460.)
Webmaster ETA: A study of the Miami Blue shows a different result – that Argentine ants do tend, may or may not defend, and apparently don’t influence the outcome. Not sure why there’s so much difference – it may be something to do with density of predators/ parasites at the two study areas.
You mention the road fire-breaks of Twin Peaks….but I don’t see how that shows any negative aspect of Mount Sutro, since the fact that the fire-breaks have never been needed points towards evidence for a lack of real fire risk.
As far as tending goes, I gave you one reference in another comment for Argentine ants tending butterfly larvae, and just saw this reference for them tending other insect larvae: http://www.springerlink.com/content/v22m7345j61q4120/. Argentine ants can be a real problem for ant-eating animals and plants that rely on larger ants for seed dispersal, but you haven’t provided any evidence that they will impact butterflies. As far as your cite for the reduction in butterfly population where no ants were present at all, it is interesting to note that that was true for G. lygdymus, the San Francisco subspecies of which already went extinct and cannot be brought back to Mt. Sutro or anywhere else in the world.
[Webmaster: Thanks for this. I looked further into it, and the Argentine ant L. Humile does tend caterpillars (Acmon Blues, and the Miami Blue). Whether it then guards them is unclear; Florida researchers Mathew Trager and Jaret Daniels found they were smaller than the native ant C. Floridanus and ran away when disturbed, while the native ant acted aggressive. But they found, surprisingly, that the ants made no difference to larval survival, which contradicts other studies. At least Arg. ants don’t seem to eat lycaenid larvae, as they do caterpillars in Hawaii.
On the matter of G. lygdymus, fortunately it’s common and not threatened. It’s only certain subspecies with limited distribution that are – like G.l. palosverdii.]
Here are the asked for references:
On alternatives to burns: Callippe Silverspot, Mission Blue, and San Bruno Elfin butterfly habitat can be managed via controlled goat/sheep grazing that takes care of the invasives and woody plants that would otherwise push out their food sources. http://www.traenviro.com/sanbruno/grazingreport/grazingplan.pdf
[Webmaster: Thanks for the refs. But this one specifically mentions fire: “The primary goal of a stewardship grazing program is the utilization of controlled livestock grazing as a tool to enhance and restore the health, diversity, and productivity of native grassland plant communities. Grazing cannot replace fire nor can fire replace grazing.”]
As you mentioned, weeding, mowing, and selective application of herbicides can and have been used to perform this task as well. [Webmaster: We mentioned herbicides are being used. Whether it performs well is open to question – especially since some larvae are very vulnerable to herbicides. Hand-weeding is an option for small areas with enough volunteers. Don’t know about mowing. Given that the butterflies need the detritus of the dead foodplants, it’s unclear if mowing would help or hurt.]
In addition, lupines and other butterfly-favorable plants can grow in microhabitats that are not well suited to other, larger plants that would push them out. [Webmaster: They can? We read that the problem was that lupines like disturbed ground but sometimes other plants get there first.] Of course, that can’t happen in the shade of enormous trees.
On the city park they survived in: http://essig.berkeley.edu/endins/callippe.htm. The name of the park is undisclosed – I know it, and you can find it if you talk to the right people, but it is not publicly disclosed due to the danger of butterfly poachers (which have been seen at the other population in San Bruno Mountain and could be particularly impacting on such a small population). [Webmaster: We’re content not to know and certainly wouldn’t publish it. Hope they’re still there.] Unfortunately, I’ve just now read another source that suggests that this park’s grassland has been altered by invasives and the population may now be extirpated. [Webmaster: That’s what the fire is supposed to prevent, by burning out the competition and giving the violas and lupines a boost against the invasives, native or naturalized.] Thankfully, a third locale has been found.
[Webmaster: According to the USFWS, “Since 1988, callippe silverspots have been recorded at San Bruno Mountain and Sign Hill near South San Francisco (San Mateo County), in the hills near Pleasanton (Alameda County), at Sears Point (Sonoma County), and in the hills between Vallejo and Cordelia.”]
You are right that there was a burn of both invasive tree stands and grassland butterfly habitat at Fort Baker – however, this was mostly considered a potential threat to the Mission Blue habitat there rather than a necessary component of it. http://www.nps.gov/fire/public/pub_fir05_goga_butterfly.cfm I haven’t seen any literature that suggested that they want burns there or that such burns would help habitat.
[Webmaster: There’s a recent NPS note on the subject. Quoting from that: This fall, the National Park Service and Golden Gate National Parks Conservancy will partner on an innovative project to restore mission blue butterfly habitat by using controlled burns and vegetation removal to create disturbance similar to that historically provided by wildfires and elk. The National Park Service and Parks Conservancy are considering this new approach after expending a great deal of effort trying to grow lupines in the field and in the nursery, but having only very limited success because of seed loss to insects and rodents, fungal pathogens, and inconsistent rainfall. A small wildfire at Fort Baker in 2004 provided just the inspiration that park managers needed in their struggle to find another way to help the mission blue. Not only did many lupines survive the fire, but so did some of the mission blue butterfly caterpillars living on them. Most importantly, new lupines sprouted up in areas that burned in much greater numbers than in places where there had been no fire. Based on the results of the Fort Baker fire, park managers are trying out a new approach to lupine restoration. Highly trained professionals from the Golden Gate Fire Management Program will use 2.5 x 2.5 meter metal “burn boxes” to produce effects similar to a wildfire in a safe and controlled way. Treatment sites within existing mission blue butterfly habitat in the Marin Headlands west of Highway 101 and at Milagra Ridge near Pacifica were chosen because they have lupines but few or no mission blue butterflies…”]
I also haven’t seen any evidence that frequent fires are part of the ecology in the Laurelwood Park/Sugarloaf Open Space of San Mateo where the butterflies are found.
As far as Mission Blues being in numbers from 1979 through 2001 – I’m having trouble locating the exact reference where I got those specific dates from, but this reference mentions regular surveying from 1979 to the present, and states that the decline didn’t begin until 1998 and lists 2005-2007 as the time period when the lack of butterflies became critical. http://www.fws.gov/ecos/ajax/docs/five_year_review/doc3216.pdf
[Webmaster: There’s a news item from the SJ Mercury news that says “In 1981, there were more than 150 butterflies on the southern end of Twin Peaks. Sixteen years later, a survey found 10 adult Mission Blue butterflies. And between 2001 and 2007, only two adults and two larvae were observed during the period, according to the action plan.”]
As far as ants and parasites go, the sources I have seen listing the habitat requirements for Mission Blues do not mention ants as a significant requirement. Some do mention parasitic wasp parasites being a major problem, but parasitic wasps were found to infect Mission Blue populations even when ants were present, and a study of San Bruno Elfins found that parasitic flies were also unaffected by the presence of symbiotic native ants. http://www.fws.gov/ecos/ajax/docs/five_year_review/doc3216.pdf
[Webmaster: The reference is embedded in another comment. It seems like it makes a significant difference for lycaenids.]
Since Argentine ants have also invaded the Marin Headlands and portions of San Bruno Mountain, this may be something that has to be dealt with in all local butterfly habitats. The good news is that at least one investigation has found that “Argentine ants operate as tending surrogates when native ants are displaced”. https://ecos.fws.gov/roar/pub/planImplementationStatus.action?documentId=400150&entityId=423.
[Webmaster: We saw that – one instance, for an Acmon Blue. It’s encouraging but not conclusive.]
However, rodents, not parasites, are the primary predator of the larva and ants can’t do anything about that. As far as ants not being necessary – this is an assertion via omission – I have never read any literature that said that ants are a necessary part of their life cycle. I’ve read several places that they are helpful, but never that they are considered a habitat requirement.
The population of Mission Blues on Twin Peaks appeared to have died out from fungal infection in the host plant due to an especially wet season, not anything that ants would have prevented. http://www.fws.gov/ecos/ajax/docs/five_year_review/doc3216.pdf [Webmaster: We read that too. Perhaps the lack of fire on Twin Peaks was partly the issue; the lupine may have faced too much competition before the fungus did them in.]
Over and over again, the primary threats to butterflies in the San Francisco area are not listed as herbicides, fire suppression, or lack of ant support, but development of their land and habitat takeover via invasive ant species. Those are the exact factors which a native restoration of Mt. Sutro would address.
[Webmaster: Or not address. It would have to be completely redeveloped, which is challenging, hugely expensive and dubiously successful. Even if it were desirable. If butterfly conservation is the focus, a better use of resources would be to preserve what’s there – even that’s proving difficult as is evident both on San Bruno Mountain and the Marin Headlands.]
Here’s another cite for you – this book talks about habitat restoration efforts for Bay Checkerspots, San Bruno Elfins, and Callippe Silverspots, states how difficult these efforts are (mostly due to the need for the right hillside topography, another argument in favor of restoration in Mt. Sutro), and then goes on to say how easy it is to restore habitat for Mission Blues. “Mission Blue habitat itself is rather easy to restore”, “it should respond particularly favorably to restoration efforts”, and “Mission Blue Butterflies have oviposited on lupines planted from seeds and containers on several restored areas on San Bruno”. That’s all from Environmental Restoration by John J. Berger. Several restored butterfly habitats in San Bruno have specifically come from the removal of eucalyptus stands. [Webmaster: Thanks for the reference, and we may track it down. We do have doubts about the ease of restoring Mission Blue turf. If it were that easy, we’d see a lot more Mission Blues. They may lay eggs on lupines, but how many of those eggs become adults? In the Twin Peaks experiment, they brought in 22 pregnant females and caged them over lupines to oviposit. But we’ve no estimate of how many butterflies resulted.]
SaveSutro says, “According to a 2001 article by Sherri Graves and UC Davis’s Professor Art Shapiro, some 82 of California’s 236 butterfly species are already known to use introduced plants for feeding and/ or breeding.”
Actually, these figures are not an accurate representation of the local situation because they are statewide figures and the distribution of both non-native plants and native butterflies is variable throughout the State. There are few non-native plants in alpine or desert regions of California. The highest proportion of non-native plants and lowest diversity of native butterflies is on the coast of California. Dr. Shapiro attributes the relatively low diversity of native butterflies on the coast to the cool climate and urban development, not the high proportion of non-native plants.
Dr. Shapiro reports that 47% of plant species in the California Central Valley are introduced. And the corresponding butterfly population is best represented by his inventory of Yolo County, where he lives. He reports that “29/32 butterfly species breed on introduced plants and 13 have no known native hosts in Davis at all.” In other words, over 90% of the native butterflies in Yolo County use non-native plants and over 40% of the native butterflies would not survive if their non-native hosts were eradicated.
Clearly, the eradication of non-native plants in California will not benefit native butterflies. Butterflies are capable of moving on. Native plant advocates would be wise to do the same. In any case, they can’t use butterflies to justify their agenda.
“Grazing cannot replace fire nor can fire replace grazing.”
To place your quote in context, that was in relation to a fully healthy and diverse native grassland community – in other words, the ideal situation, which is not what we have any longer anywhere in the San Francisco Bay area. Some of our native plants (such as manzanita) need to specifically have fire to reproduce, though I don’t think that applies to any of the butterfly-relevant plant species we have been talking about. Grazing can still be used as a tool in butterfly habitats when the ideal isn’t possible. In fact, the Callippe Silverspot range article you later cite not only mentions Twin Peaks as a former site for the butterflies, but specifically calls for grazing (and not fire) as a means to manage the butterfly habitat.
The Mission Blue recovery plan specifically states (as I cited) that the decline on Twin Peaks is believed to have been caused by the fungal infections that started in 1998. Perhaps the news article just missed it by a couple years when they gave you “16 years later” after 1981? I have found sources citing both plants and larvae numbering over 100 in 2000, but not specifics on adults.
Multiple cites listed only two populations for Callippe Silverspots, and then the ” hills between Vallejo and Cordelia” has been listed as the third population – now 2nd, since the Alameda County population appears to have gone extinct. The Pleasanton and Sears Point populations are listed in some references as being uncertain in terms of subspecies ID, but I’ll assume it’s been resolved since your cite is newer – that’s nice that it’s 4 populations instead of 2, but still not great.
In looking at these references, I might have to take back my earlier comment that Twin Peaks/Mt. Sutro is not the best spot for Callippes. The USFWS Calllippe Silverspot recovery plan (draft updated 8/12/10) specifically lists Twin Peaks as one of the eight core areas to be targeted for the preservation of the species, along with the 4 localities you mentioned and 3 localities where they may occur:
“Twin Peaks in San Francisco potentially has sufficient area to support a small callippe silverspot butterfly population. It is closest to the type locality for the species, and would have significant conservation and educational value as a restoration site, making it the eighth core area for conservation action.”
So that would make the Mt. Sutro/Twin Peaks area a good target for endangered Mission Blues, Bay Checkerspots, AND Callippe Silverspots, possibly San Bruno Elfins and Myrtle Silverspots as well, and potentially a number of the other 56 butterfly species native to San Francisco.
Milliontrees, the vast majority of plant habitat in Yolo County has been converted to agriculture. It is extremely non-representative of San Francisco or any other part of California outside of the Central Valley. Your numbers specifically quote Davis – a city surrounded by agriculture on all sides with no significant native habitat left at all. The reason that so many butterflies don’t have native plants there is because there’s so few native plants to be had – the only butterflies that survive in the majority of Yolo County are those that can survive on agricultural land.
In such a situation, no one would destroy the crops without replanting with native vegetation, so your suggestion of butterfly extirpation due to nonnative plant removal is a red herring. Nothing about the situation you describe applies to eucalyptus forest and San Francisco’s butterflies. Your statement that “butterflies are capable of moving on” has clearly been shown to be false by the extinction of 3 San Francisco species already, the extirpation of 17 more, and the near-extinction of at least 5.
[Webmaster: Perhaps we should clarify no species of butterfly has gone extinct here; these are localized subspecies. At the species level, they are not endangered, though some subspecies are.]
Great Post 😀
thought you might like my machinima film the butterfly’s tale~
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