FRIENDS OF EDGEWOOD NATURAL PRESERVE
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FRIENDS OF EDGEWOOD NATURAL PRESERVE
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RETURN OF THE BUTTERFLIES By Bill Korbholz
By this time next year, hundreds of Bay checkerspot butterflies will be flitting again at Edgewood Natural Preserve. The reintroduction of this animal is the culmination of work begun in 2001 by Dr. Stuart B. Weiss, Ph.D., Consulting Ecologist, Creekside Center for Earth Observations. The nutrient poor serpentine grasslands at Edgewood previously supported one of the very few remaining populations of the butterfly, a federally threatened species, on the San Francisco Peninsula. Its population numbered in the thousands in the mid-1990's, but by 2000 had crashed to under 100. In 2002 the population dropped to zero, the victim of “drive-by extinction,” as Weiss puts it. Emissions of ammonia and nitrogen oxides from 100,000+ vehicles on Highway 280 have fertilized a substantial area of serpentine grassland and allowed for invasion of Italian ryegrass onto the nutrient-poor soils. The result: lots of ryegrass that has outcompeted the native plants on which the butterfly depends for food. While in its caterpillar form, this insect loves to munch California plantain, a plant that has adapted to thin serpentine soil conditions. If it can’t find plantain, it will settle for Owl’s clover. These native plants are easily overwhelmed by the ryegrass. From 2001 to 2004, Weiss conducted experiments on Edgewood’s grasslands to determine the optimum treatment techniques to reduce the ryegrass and increase the native plant cover. He concluded that a combination of mechanical mowing and weedwhacking worked best.
Having proved that native serpentine grasslands can be sustained, Weiss intends to reintroduce the butterfly by transplanting both caterpillars and butterflies from Coyote Ridge just south of San Jose east of Highway 101 where the butterfly population is thriving. Reintroduction is planned for early spring 2007. Much of Weiss’s work has been funded by grants from the US Fish and Wildlife Foundation and PG&E. This year REI awarded a grant to the Friends of Edgewood (see the March 2006 issue of the Explorer), and after consulting with Weiss and Parks & Rec staff, we decided to devote it to habitat restoration and sharing this inspiring story with the public. We plan to produce some interpretive display boards and an attractive full-color brochure describing the butterfly’s amazing story. These educational materials will remain valuable for years to come, as hand-outs at docent-led wildflower walks, various Edgewood events (such as Earth Day), and school group outings. We also hope to invite community-wide participation in some celebratory events to help us herald the return of our beloved butterfly to Edgewood. |
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Last year
nearly 8 acres were treated, and this year another 8.5 were added. A side-effect
of the mowing is that the native flowering plants love it. Visitors this season
were dazzled by the vibrant colors coming from the mow sites.