title: Projected evolution of California's San Francisco Bay-Delta-river system in a century of climate change.
abstract: BACKGROUND
  Accumulating evidence shows that the planet is warming as a response to human emissions of greenhouse gases. Strategies of adaptation to climate change will require quantitative projections of how altered regional patterns of temperature, precipitation and sea level could cascade to provoke local impacts such as modified water supplies, increasing risks of coastal flooding, and growing challenges to sustainability of native species.
  
  
  RESULTS
  We linked a series of models to investigate responses of California's San Francisco Estuary-Watershed (SFEW) system to two contrasting scenarios of climate change. Model outputs for scenarios of fast and moderate warming are presented as 2010-2099 projections of nine indicators of changing climate, hydrology and habitat quality. Trends of these indicators measure rates of: increasing air and water temperatures, salinity and sea level; decreasing precipitation, runoff, snowmelt contribution to runoff, and suspended sediment concentrations; and increasing frequency of extreme environmental conditions such as water temperatures and sea level beyond the ranges of historical observations.
  
  
  CONCLUSIONS
  Most of these environmental indicators change substantially over the 21(st) century, and many would present challenges to natural and managed systems. Adaptations to these changes will require flexible planning to cope with growing risks to humans and the challenges of meeting demands for fresh water and sustaining native biota. Programs of ecosystem rehabilitation and biodiversity conservation in coastal landscapes will be most likely to meet their objectives if they are designed from considerations that include: (1) an integrated perspective that river-estuary systems are influenced by effects of climate change operating on both watersheds and oceans; (2) varying sensitivity among environmental indicators to the uncertainty of future climates; (3) inevitability of biological community changes as responses to cumulative effects of climate change and other drivers of habitat transformations; and (4) anticipation and adaptation to the growing probability of ecosystem regime shifts.
authors.affiliation: U.S. Geological Survey, Menlo Park, California, United States of America. jecloern@usgs .gov
authors.forename: James E
authors.initials: JE
authors.lastname: Cloern
authors.forename: Noah
authors.initials: N
authors.lastname: Knowles
authors.forename: Larry R
authors.initials: LR
authors.lastname: Brown
authors.forename: Daniel
authors.initials: D
authors.lastname: Cayan
authors.forename: Michael D
authors.initials: MD
authors.lastname: Dettinger
authors.forename: Tara L
authors.initials: TL
authors.lastname: Morgan
authors.forename: David H
authors.initials: DH
authors.lastname: Schoellhamer
authors.forename: Mark T
authors.initials: MT
authors.lastname: Stacey
authors.forename: Mick
authors.initials: M
authors.lastname: van der Wegen
authors.forename: R Wayne
authors.initials: RW
authors.lastname: Wagner
authors.forename: Alan D
authors.initials: AD
authors.lastname: Jassby
mesh_terms: D000818:Animals; D061006:Bays; D005075:Biological Evolution; D058448:Biota; D057231:Climate Change / Q000706:statistics & numerical data*; D003247:Conservation of Natural Resources / Q000639:trends; D055868:Floods / Q000706:statistics & numerical data; D006801:Humans; D012306:Risk; D045483:Rivers; D012495:San Francisco; D014881:Water Supply / Q000706:statistics & numerical data