Checkerspot on the news

anne kilmer viceroy at
Mon May 8 13:13:39 EDT 2000


           Although widely seen an ecological no-no, grazing turns out
to be essential to a
           threatened butterfly in the San Francisco Bay Area. This
conservation twist is due
           to connections between the butterflies, cows and cars,
according to new research
           presented in the December issue of Conservation Biology. 

           "My work untangles a complex web of ecological and human
interactions," says
           Stuart Weiss of the Center for Conservation Biology at
Stanford University. 

           The basic story is that cars and other smog sources deposit
extra nitrogen on
           nutrient-poor grasslands in the San Francisco Bay Area. This
extra nitrogen
           enhances the invasion of non-native grasses, which displace
the plants that Bay
           checkerspot butterflies depend on. Cows help the butterflies
by eating the
           non-native grasses, which allows the native plants to grow. 

           The two-inch, red-cream-and-black Bay checkerspot butterflies
live only on
           outcrops of serpentinitic rock, which are unique partly
because they have low
           nitrogen and patches of heavy metals. Serpentinitic
grasslands have more than 100
           species of native plants, several of which are endangered. 

           Weiss discovered that grazing benefits Bay checkerspot
butterflies by studying
           several serpentinitic sites in south San Jose. The sites had
been grazed for decades
           but when grazing ceased at two of them in the mid-1990s, the
butterfly populations
           there rapidly went extinct. In contrast, butterfly
populations persisted at a site
           where grazing continued. 

           The most obvious difference between the grazed and ungrazed
sites was that the
           latter quickly became overrun by non- native grasses such as
wild oats and Italian
           ryegrass. Previously, these sites had had dense stands of
native plants; plants that
           Bay checkerspot larvae eat include California plantain and
owl's clover, and
           plants that provide nectar for the adult butterflies include
goldfields, tidy tips and
           wild onion. 

           To demonstrate the link between non-native grasses and extra
nitrogen in the
           butterfly's habitat, Weiss estimated how much airborne
nitrogen was deposited on
           serpentinitic grasslands in south San Jose. He found that
nitrogen levels were at
           least 10 pounds per acre per year, which over the course of
several years is
           similar to the amounts typically used in experiments on the
effects of fertilization. 

           Weiss draws two main conservation lessons from his research.
First, moderate
           grazing can benefit nitrogen-sensitive ecosystems by
controlling non-native
           grasses and removing excess nitrogen. However, grazing is not
perfect so he
           recommends testing fire and other methods for controlling
non-native grasses. 

           Second, because the San Francisco Bay Area meets federal and
state standards for
           airborne nitrogen NOx, human health standards do not
necessarily protect
           nitrogen-sensitive ecosystems. "Nitrogen deposition is
becoming recognized as a
           major component of global change," says Weiss. In the U.S.,
nitrogen deposition is
           particularly high in the Sierra Nevada foothills, the
mountains of Southern
           California, the Midwest and the East. 

           For more information, contact Stuart Weiss (650-725-9915,
           stu at 


           A Bay checkerspot butterfly 
           A fenceline between grazed and ungrazed areas, showing
flowers on one side and
           lush non-native grasses on the other 

Nick Greatorex-Davies wrote:
> Do you have a reference for that Anne. We did a paper a few years ago
> that looked at the spread of coarse grasses on a nature reserve here
> in the UK and changes (mostly increases) in numbers of some grass
> feeding butterflies and moths (Pollard et al (1998) Biological
> Conservation 84 17-24). One of the possible reasons for the increase
> in coarse grasses, we speculated was atmospheric nitrogen deposition
> (eg from exhaust emissions for cars), but we had no direct. evidence
> for this.
> Nick
> Mr J Nick Greatorex-Davies
> (Butterfly Monitoring Scheme co-ordinator)
> NERC Centre for Ecology and Hydrology
> Monks Wood
> Abbots Ripton
> Huntingdon
> Cambridgeshire PE28 2LS  UK
> Tel: (+44) (0) 1487 773 381
> Fax: (+44) (0) 1487 773 467
> E-mail: ngd at
> >>> anne kilmer <viceroy at> 07/05/00 06:21:44 >>>
> I have pursued this on the glorious Web ...
> They're finding that the nitrogen in vehicle emissions causes
> non-native
> grasses to crowd out the native host plants that the Bay checkerspot
> uses.
> They now use cows (!) to graze down the grasses and find that the
> butterfly returns.
> Anybody think they're grazing the embattled area?
>  Cows are not an elegant solution anyway. I suppose the little man
> with
> the bucket and spade is gathering the manure, but hooves dig up
> fragile
> soil, destroy other plants, and cows are not that particular as to
> what
> they eat.
> Sheep and goats would be worse.
> Any votes for Boy Scouts with Roundup onna stick?
> Second graders with nail scissors?
> The requirements for the bugs are frighteningly precise ... maybe
> we'll
> win, and I'm glad we're trying, but oh Lordy, Lordy.
> Here's a nice site.
> Anne Kilmer
> Mayo, Ireland
> Doug Yanega wrote:
> >
> > >
> > >
> > >Would that be the Chalcedon checkerspot, do you think?
> >
> > No, it would Euphydryas e. editha, known as the Bay Checkerspot
> (the name
> > "bayensis" is not valid). It *IS* Federally listed, and if it
> occurs on the
> > property in question (it's certainly the right area), then
> theoretically
> > there should be significant difficulties in getting the land
> developed.
> > Five years with no sightings is certainly possible on an inhabited
> piece of
> > property, though it all depends on the credibility of the
> consultants doing
> > the surveys. One certainly does hear of consulting firms who
> conveniently
> > fail to report positive sightings, or contract out to marginally
> competent
> > field people who don't do a thorough job of surveying.
> >
> > Doug Yanega        Dept. of Entomology         Entomology Research
> Museum
> > Univ. of California - Riverside, Riverside, CA 92521
> > phone: (909) 787-4315 (standard disclaimer: opinions are mine, not
> UCR's)
> >  
> >   "There are some enterprises in which a careful disorderliness
> >         is the true method" - Herman Melville, Moby Dick, Chap. 82

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