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Stu Weiss

Smog is Fertilizer: The Long and Winding Road from the Pages of Conservation Biology to a Regional Habitat Conservation Plan.


The road from scientific discovery to conservation action is rarely straight, narrow, nor fast. I will recount how a revelation in 1993 –nitrogen fertilization from Silicon Valley smog threatened the ESA-listed Bay checkerspot butterfly by driving annual grass invasions in serpentine grasslands, and cattle grazing was the key to controlling the impacts – was published in 1999, and leveraged to create the Santa Clara Valley Habitat Plan. Mitigation precedents for powerplant nitrogen emissions led to freeway mitigation that included a commitment to a regional Habitat Conservation Plan in 2001. After more than 10 years of additional science and advocacy, including passive sampling of N-deposition gradients and modeling, stakeholder education about N-deposition, scientific networking through a long-running AGU session, “Operation Flower Power” tours for elected officials and stakeholders, and building a “Habitat Conservation Now” coalition, the Habitat Plan was adopted in 2013. The 50-year, $665,000,000 HCP/NCCP promises coordinated conservation and long-term stewardship. The first major conservation acquisition, >500 ha of serpentine grasslands, was closed in 2015. The Bay checkerspot butterfly has become a poster child for threats of N-deposition to biodiversity, and the Santa Clara Valley experience provides one model for addressing this profound, but underappreciated environmental change.


Stu Weiss, Ph.D. (Stanford University) is Chief Scientist of Creekside Science, which provides scientific and conservation expertise to diverse organizations as they cope with the rapidly changing 21st Century environment.  He has researched the Bay checkerspot butterfly and serpentine grasslands since 1979, and has authored numerous scientific papers concerning climate/microclimate, population dynamics, nitrogen deposition, and conservation ecology.  Creekside Science executes many hands-on restoration projects, including butterfly reintroductions, propagation of endangered plants, and habitat monitoring and management.  His research into nitrogen deposition impacts on biodiversity and passionate advocacy were instrumental in the development of the Santa Clara Valley Habitat Plan.  He is Science Advisor for the Bay Area Conservation Lands Network.  For more information see