ARTICLE Sea change under climate change: case studies in rare plant conservation from the dynamic San Francisco Estuary 1 Brenda J. Grewell, Erin K. Espeland, and Peggy L. Fiedler Abstract: We present case studies supporting management of two rare plant species in tidal wetlands of the San Francisco Estuary. We used empirical demographic analyses to identify factors to enhance population establishment and survival of Chloropyron molle subsp. molle (Orobancaceae), an annual hemiparasite, and to compare reintroduced with natural populations. Twelve years after outplanting, the reintroduced population persists but is in decline; impediments to success include the lack of adaptive management response to weed invasions and muted variance in hydrology. Transplantation of Lilaeopsis masonii (Apiaceae), a rhizomatous perennial herb, failed to meet success criteria for mitigation 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 has few threats to persistence so long as suitable habitat is present. These two examples 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. Key words: plant reintroduction, wetland restoration, adaptive management, climate change, Chloropyron molle subsp. molle, Lilaeopsis masonii. Résumé : Les auteurs présentent des études de cas supportant l’aménagement de deux espèces de plantes rares des terres humides intertidales dans l’estuaire de San Francisco. Ils ont utilisé des analyses démographiques empiriques pour identifier les facteurs susceptibles d’accroître l’établissement et la survie du Chloropyron molle subsp. molle (Orobranchaceae), une hémiparsite, et ils ont comparé les populations naturelles et introduites. Douze ans après la plantation, la population réintroduite persiste, mais décline; le blocage inclut le manque de réaction adaptative de l’aménagement a ` l’invasion par des herbes adventices et des modifications de variances de l’hydrologie. La transplantation du Lilaeopsis masonii (Apiaceae), une herbe pérenne a ` rhizome, n’a pas satisfait les critères de succès pour la mitigation a ` l’échelle locale du projet, mais la dispersion et l’établissement de métapopulations en colonies indiquent sa persistance a ` l’échelle du paysage. On a constaté que cette espèce est génétiquement distincte d’une congénère largement étendue, et ne connaît pas de menace a ` son existence, pourvu qu’il s’y trouve un habitat convenable. Ces deux exemples démontrent le besoin d’intégrer les stratégies d’aménagement de conservation pour supporter la dispersion en réaction a ` l’élévation du niveau de la mer. Pour la plante hémiparasite, la colonisation assistée peut supporter les populations menacées par l’élévation du niveau de la mer, mais seulement si on assure un suivi efficace. [Traduit par la Rédaction] Mots-clés : réintroduction de végétaux, restauration de terres humides, aménagement adapté, changement climatique, Chloropy- ron molle subsp. molle, Lilaeopsis masonii. Introduction Conservation of threatened and endangered plant species his- torically has hinged on the legal listing of species. Requisite recov- ery plans and measures for habitat protection have been prepared for far fewer species than are listed. When endangered species face a single threat, such as overharvesting (e.g., Nantel et al. 1996) or other direct disturbance, in situ mitigation of that single threat often leads to successful recovery (Lawler et al. 2002, but see Cruse-Sanders and Hamrick 2004). In this case, protection of rare plant population sites and currently suitable, but unoccupied hab- itats is an appropriate prescription to increase population sizes, restructure age and (or) size distributions within depleted popu- lations, and decrease extirpation rates. The recovery of endan- gered plants in human-altered landscapes also may require creation of new populations in restoration efforts (Falk et al. 1996; Boersma et al. 2001). For two decades, the challenging practice of plant reintroduction (i.e., creation of new populations within their historic range) has been an integral part of recovery strate- gies, though outcomes for such plant populations are uncertain (Godefroid et al. 2011; Guerrant 2012). Finding appropriate sites for reintroduction requires careful evaluation of physical, biological, historic, and logistical factors; however, sufficient information is not always available (Fiedler and Laven 1996; Maschinski et al. 2012). As the knowledge base of the science and practice of rein- troduction has grown, conservationists have developed a more dynamic view of habitat as being comprised of variable, interact- ing ecological processes (Suding and Gross 2006). As we learn more about how integrated physical and biological factors deter- mine the population dynamics of many endangered plant species (e.g., Espeland et al. 2005), it is clear that effective management of Received 7 December 2012. Accepted 18 March 2013. B.J. Grewell. USDA-ARS Exotic & Invasive Weeds Research Unit, University of California, Davis, Department of Plant Sciences Mail Stop 4, 1 Shields Avenue, Davis, CA 95616, USA. E.K. Espeland. USDA-ARS Northern Plains Agricultural Laboratory Pest Management Research Unit, 1500 North Central Avenue, Sidney, MT 59270, USA. [USDA is an equal opportunity provider and employer.] P.L. Fiedler. Natural Reserve System, University of California, Office of the President, 1111 Franklin Street, 6th Floor, Oakland, CA 94607, USA. Corresponding author: Brenda J. Grewell (e-mail: bjgrewell@ucdavis.edu). 1 This article is part of a Special Issue entitled “Transplantation and reintroduction of species at risk: learning from the past to plan for the future”. 309 Botany 91: 309–318 (2013) dx.doi.org/10.1139/cjb-2012-0300 Published at www.nrcresearchpress.com/cjb on 8 April 2013. Botany Downloaded from www.nrcresearchpress.com by Calif Dig Lib - Davis on 05/13/13 For personal use only.