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Cars, cows, and checkerspot
butterflies: Preserving the serpentine ecosystem in Santa Clara County
by Stuart Weiss
Ridge, a thousand feet above the valley floor, dazzling carpets of
California wildflowers - goldfields, yellow and white tidy-tips, red wild
onions, purple linanthus and owl's clover, silvery dwarf plantain, orange
poppies, dozens of species - fold over ridges and canyons studded with
lichen-covered outcrops of greenish serpentine rock.
Habitats on opposite sides of
this fenceline demonstrate just how significant cattle grazing can be
in native ecosystems. Cattle selectively graze the tall, nonnative grasses
on the far side of the fence, allowing native plants -- and the other
species that depend on them -- to thrive.
Red, black and cream colored Bay checkerspot
butterflies sip nectar from the tidy-tips and wild onions; three male
butterflies chase a female laden with eggs, while others bask in the bright
April sun. Tiny Bay checkerspot caterpillars eat dwarf plantain and owl's
clover at my feet. A golden eagle soars upwind, above traffic jams on
Highway 101, fields, orchards, and golf courses of Coyote Valley, and
Silicon Valley sprawl fading northward into brownish smog.
I ascend the ridgetop, and two bachelor tule elk bolt east down a canyon,
toward the dry upper reaches of Anderson Lake - beyond which Mt. Hamilton,
dusted with snow from a late season storm, anchors vast expanses of oak
woodlands and chaparral. The squish of a fresh cow pie interrupts my reverie,
and I look across a barbed wire fence where the short flowers disappear
into a tall sward of Eurasian grasses.
Coyote Ridge, our regional biodiversity hotspot
My boot is firmly planted at the epicenter
of a local biodiversity hotspot - and an intricate scientific and conservation
vortex. Thousands of acres of rocky, nutrient-poor serpentine soils on
Coyote Ridge provide refuge for native flora, plant species crowded off
richer soils by invasive Eurasian grasses and forbs. The Bay
checkerspot butterfly, protected under the Endangered
Species Act, absolutely requires several species of small annual native
plants as caterpillar food and adult nectar, and is literally trapped
on islands of serpentine soils. Bay checkerspot butterfly populations
are more volatile than the NASDAQ, booming and busting according to yearly
weather. Because the wrinkled terrain of Coyote Ridge offers innumerable
microclimates that buffer populations from California's periodic droughts
and El Nino deluges, this extensive habitat is the butterfly's main, and
perhaps only, chance to avoid extinction.
Despite the listing of the butterfly in 1987 as a "threatened"
species, by the year 2000 fewer than 100 acres of habitat out of thousands
remaining were both permanently protected and well-managed. The listing
of four endemic plants in the 1990s did little more for conservation.
Hundreds of acres of serpentine have already been lost to subdivisions,
landfill, and golf courses, with other development proposals in the works.
But saving habitat from big yellow Caterpillar tractors is only part of
the battle. The other portion sits underfoot, and across the barbed wire
Cows...in native ecosystems?
Amazingly, this ecosystem is an example
of how cows - yes, cows - can help maintain native biodiversity. Whenever
grazing cattle are removed from South Bay serpentine grasslands, the diminutive
native wildflowers used for caterpillar food and adult nectar are overrun
by Eurasian grasses, and butterfly populations go extinct. In our own
local "environmental train wreck," the deliberate removal of
cattle from disputed land in the Silver Creek Hills in the 1990's led
to extinction of a robust butterfly population, regulatory standoffs,
lawsuits, political arm-twisting, and hundreds of acres of habitat degradation.
Serpentine grasslands in Santa Teresa County Park, protected from development,
are devoid of butterflies because they are devoid of cows, like the habitat
across the fence. How is it that we actually need cows to protect native
Clouds on the horizon
The answer wafts in on northwest breezes
gathering smog from the Peninsula and Silicon Valley, eventually bathing
Coyote Ridge in reactive nitrogen gases that effectively serve as slow-release
fertilizer. Each year, smog deposits about 10 pounds of nitrogen on each
acre of grassland, alleviating the main nutrient limitation of serpentine
soils. Without cows to keep them under control, annual grasses can then
rapidly invade. The cattle selectively eat these nitrogen-rich annual
grasses, thus removing nitrogen from the system (as beef) and redistributing
nitrogen within the system. Cows eat globally and deposit locally, as
evidenced by the fence line and my messy boot.
Power plant provides conservation opportunity
The advent of Calpine Corporation's
Center, a 600 MW gas-fired power plant at the north end of the Coyote
Valley, converted nitrogen deposition into innovative conservation policy.
Calpine, the California Energy Commission, and the US
Fish and Wildlife Service (USFWS) worked together to develop a mitigation
strategy for NOx (nitrogen) and ammonia emissions from the plant, preserving
serpentine acreage in exchange for incremental deposition. In April 2002,
116 acres of Tulare Hill and 15 acres on Coyote Ridge were transferred
to the Land Trust of Santa Clara County - along with a $1.4 million endowment
for management and monitoring in perpetuity.
Mitigation for the Calpine Energy Center
at the north end of Coyote Valley (pictured here) is leading to the development
of a regional Habitat Conservation Plan that could help provide broad
habitat protection for Santa Clara County.
The Calpine mitigation set a regulatory precedent
and roadmap, so the next major projects that increase local NOx emissions
- traffic from Highway 101 widening and Coyote Valley Research Park -
were persuaded by USFWS to commit to preservation of 669 acres of habitat.
Furthermore, Santa Clara County, San Jose, Valley Transportation Authority,
and the Santa Clara Valley Water District are developing a regional Habitat
Conservation Plan (HCP) that could lead to preservation and management
of virtually the entire remaining serpentine ecosystem, as well as habitat
for the red-legged frog and other listed species.
Environmental change requires innovative
approaches to conservation
If effectively developed and executed, the HCP will provide a template
for broad-scale habitat protections for imperiled biodiversity of Santa
Clara County. Committee for Green Foothills, Santa
Clara Valley Audubon Society, the California
Native Plant Society, and other local groups are carefully monitoring
the nascent HCP process. Organizations such as the Santa
Clara County Open Space Authority, Land Trust of Santa Clara County,
The Nature Conservancy,
and private foundations will undoubtedly play a major role in land acquisition
and management, along with funding and political leadership by local,
state, and federal governments.
As I wipe off my boot on a fencepost, my thoughts range beyond the snowy
crest of Mt. Hamilton. Conservation in our age of global environmental
flux - with unpredictable changes brought by invasive species, changing
nutrient levels, land-use pressures, and climatic extremes - cannot be
as simple as fencing off land and letting it go. The serpentine ecosystem
at Coyote Ridge is a microcosm of such changes, and creating innovative
and effective solutions for its conservation and management will be a
Stuart B. Weiss is a freelance conservation biologist who has been
studying checkerspot butterflies and serpentine ecology since 1979. He
received his Ph.D. from Stanford in 1996, and is author on more than 25
Published October 2002 in Green
Page last updated
September 13, 2010