Sea change under climate change: case studies in rare plant conservation from the dynamic San Francisco Estuary

Authors: Grewell, Brenda; Espeland, Erin; FIEDLER, PEGGY - University Of California

Submitted to: Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2013
Publication Date: 4/8/2013
Citation: Grewell, B.J., Espeland, E.K., Fiedler, P.L. 2013. Sea change under climate change: case studies in rare plant conservation from the dynamic San Francisco Estuary. Botany. 91:309-318.

Interpretive Summary: This article is an invited contribution to a special issue of the peer-reviewed journal Botany that focuses on transplantations and relocation of plant species at risk in the face of climate change. This article includes two case studies that support management of two rare plant species in tidal wetlands in San Francisco Estuary. Soft bird’s-beak is an endangered hemiparasitic plant that is dispersal limited, highly impacted by weed invasions, and is further threatened by sea level rise. The second species, Mason’s lilaeopsis, is a rhizomatous perennial species that grows is regularly submersed in the intertidal zone, readily disperses with metapopulation dynamics, and may recolonize naturally if suitable habitat is conserved. We demonstrate how demographic analyses and survival models support evaluation of the reintroduction of soft bird’s beak. In the case of Mason’s lilaeopsis, molecular analyses prove the species is genetically indistinct from a widespread congener and therefore is rare only in the legal sense. The data presented in these two examples highlight some important, unresolved issues in conserving rare species in the face of plant invasions and climate change. Both examples demonstrate the need for active stewardship and integrated conservation strategies that include invasive weed management, prioritize habitat connectivity and maintain physical processes to support dispersal in response to sea level rise.

Technical Abstract: We present case studies supporting management of two rare plant species in tidal wetlands of the San Francisco Estuary. For an annual hemiparasite, we used demographic analyses to identify factors to enhance population establishment, survivorship and fitness, and to compare reintroduced with natural populations. Twelve years following establishment, the reintroduced population persists but is in decline; impediments to success have been the lack of adaptive management response to weed invasions and muted variance in hydrology. For a rhizomatous perennial herb believed to be rare in regularly flooded intertidal zones, transplantation for mitigation failed to meet success criteria at local project scale, but dispersal and establishment of metapopulation patches indicated persistence at the landscape scale. This species has been found to be genetically indistinct from a widespread congener and therefore is rare only in the legal sense, and has few threats to persistence so long as suitable habitat is present. The data presented in these two examples highlight some important, unresolved issues in conserving rare species in the face of plant invasions and climate change. The case studies demonstrate the need for integrated conservation management strategies that prioritize habitat connectivity and maintain physical processes to support dispersal in response to sea level rise. For the hemiparasite, assisted colonization may sustain populations threatened by sea level rise, but only if a strong commitment to effective stewardship is realized.