The once common bay checkerpoint butterfly faces extinction because of habitat loss due to automotive exhaust.
Historically, Euphydryas editha bayensis was found all around the San Francisco Bay Area, from San Francisco to Contra Costa County and south to Hollister. This butterfly depends plants adapted to "serpentine" derived soils, which are high in magnesium and heavy metals and low in nitrogen because they're formed from rocks from the ocean floor.
It turns out that car exhaust on I-280 through San Mateo County contributes enough nitrogen to the soil to encourage growth of invasive grasses and drive out the native, serpentine plants on which the checkerpoint butterfly depends for survival. Biologist Stuart Weiss calls the decline of this butterly "drive by extinction," and butterfly lovers encourage drivers on I-280 to slow down to the speed limit to lower their emissions and, hopefully, save a few butterflies.
In other news: Santa Cruz County lacks funding for even the most basic road maintenance projects. There are more than a handful of roads in the county where a full lane is washed out, and the only mitigation the county can afford are a couple of orange safety cones.