San Francisco Bay

Re-Oaking North Bay: A strategy for restoring native oak ecosystems, focusing on Napa and Sonoma valleys

San Francisco Estuary Institute (SFEI) | July 7th, 2020

Oaks are iconic trees in California, the defining feature of savannas and woodlands in many parts of the state. For millennia, these majestic trees have provided the e

Oaks are iconic trees in California, the defining feature of savannas and woodlands in many parts of the state. For millennia, these majestic trees have provided the ecological foundation upon which thousands of other organisms depend. Their cultural significance is equally profound: they are of central importance to diverse indigenous groups, and are prized for the many benefits they provide California residents. Vast expanses of oak savanna historically occupied the rich alluvial soils of Napa and Sonoma valleys. The immense and long-lived valley oak (Quercus lobata) dominated these savannas, accounting for more than 65% of trees (Dawson 2008, Grossinger et al. 2012). Early observers described the valleys as “studded with groups of oaks” (Marryat 1850), and extolled the “magnificent oaks” that were “the glory of the landscape scenery” (Smith and Elliott 1878). Black oak (Q. kelloggii), coast live oak (Q. agrifolia), and other oak species were present in smaller numbers on the valley floors and were more abundant in the hillsides (Dawson 2008, Grossinger et al. 2012). Over the past two centuries, however, much of this oak savanna has been cleared to make way for orchards, vineyards, and towns. In Napa Valley, the number of mature trees has declined from an estimated 45,000 in the early 1800s to less than 1,000 today (Grossinger et al. 2012). Valley oak habitat has been particularly affected by clearing and fragmentation: in many areas of the state, loss of valley oak woodland exceeds 90% (Kelly et al. 2005, Whipple et al. 2011). Documentation of this loss, and recognition of the value of oaks for both people and nature, has led to a growing desire to restore this unique ecosystem and bring back many of the benefits that oaks provide. Despite the significant changes the North Bay landscape has experienced since European settlement, there are opportunities to restore oaks in settings as diverse as backyards, parks, streets, farms, vineyards, and creeksides.

Re-Oaking Silicon Valley: Building Vibrant Cities with Nature

San Francisco Estuary Institute (SFEI) | August 1st, 2017

In this report, we investigate how integrating components of oak woodlands into developed landscapes — “re-oaking” — can provide an array of valuable functions fo

In this report, we investigate how integrating components of oak woodlands into developed landscapes — “re-oaking” — can provide an array of valuable functions for both wildlife and people. Re-oaking can increase the biodiversity and ecological resilience of urban ecosystems, improve critical urban forest functions such as shade and carbon storage, and enhance the capacity of cities to adapt to a changing climate. We focus on Silicon Valley, where oak woodland replacement by agriculture and urbanization tells a story that has occurred in many other cities in California. We highlight how the history and ecology of the Silicon Valley landscape can be used as a guide to plan more ecologically resilient cities in the Bay Area, within the region and elsewhere in California. We see re-oaking as part of, and not a substitute for, the important and broader oak woodland conservation efforts taking place throughout the state.  

Recent advances in understanding flow dynamics and transport of water-quality constituents in the Sacramento–San Joaquin River Delta

University of California, Davis (UC Davis) | December 1st, 2016

This chapter describes advances during the past decade in understanding flow dynamics and how water-quality constituents, such as salinity, heat, oxygen, nutrients, conta

This chapter describes advances during the past decade in understanding flow dynamics and how water-quality constituents, such as salinity, heat, oxygen, nutrients, contaminants, and more, move within California’s Sacramento-San Joaquin River Delta. Water-quality constituents are affected by water diversions and other human manipulations of flow and they greatly affect the quantity and quality of habitats in the Delta. Along with human intervention, the Pacific Ocean, the Central Valley watershed, and the atmosphere, are a few drivers of flow and transport in the Delta. These drivers provide a conceptual framework for presenting recent findings. The tremendous expansion of acoustic and optical instruments utilized in the Delta over the past decade has greatly improved our understanding of how tidal variability affects flow and transport. Sediment is increasingly viewed as a diminishing resource needed to sustain habitat and tidal marsh, especially as sea level rises. Connections between the watershed, Delta, and San Francisco Bay that have been studied recently highlight that a landscape view of this system is needed rather than consideration of each region individually. Interactions of multiple drivers and information gaps are discussed.

Recent California Water Transfers: Implications for Water Management

Natural Resources Journal (University of New Mexico) | January 3rd, 1995

The 1991 and 1992 California Drought Emergency Water Banks were the first large water transfer programs in the nation in which the state served as the predominant broke

The 1991 and 1992 California Drought Emergency Water Banks were the first large water transfer programs in the nation in which the state served as the predominant broker for water trades. Although the state-sponsored Water Banks have drawn widespread attention, there have been a great number of water transfers and exchanges taking place in California independently of the state. These transfers illustrate well the widespread applicability of transfers in managing water resource systems, as well as the multiple mechanisms available for effecting water transfers. This article focuses on California's recent experiences with water transfers, and offers a series of potential lessons for federal, state, and local managers for integrating water transfers in regional water resource systems.

Recent declines in salmon body size impact ecosystems and fisheries

Nature Portfolio (Springer Nature) | August 19th, 2020

Declines in animal body sizes are widely reported and likely impact ecological interactions and ecosystem services. For harvested species subject to multiple stressors, l

Declines in animal body sizes are widely reported and likely impact ecological interactions and ecosystem services. For harvested species subject to multiple stressors, limited understanding of the causes and consequences of size declines impedes prediction, prevention, and mitigation. We highlight widespread declines in Pacific salmon size based on 60 years of measurements from 12.5 million fish across Alaska, the last largely pristine North American salmon-producing region. Declines in salmon size, primarily resulting from shifting age structure, are associated with climate and competition at sea. Compared to salmon maturing before 1990, the reduced size of adult salmon after 2010 has potentially resulted in substantial losses to ecosystems and people; for Chinook salmon we estimated average per-fish reductions in egg production (−16%), nutrient transport (−28%), fisheries value (−21%), and meals for rural people (−26%). Downsizing of organisms is a global concern, and current trends may pose substantial risks for nature and people.

Recent decreases in snow water storage in western North America

Nature Portfolio (Springer Nature) | May 22nd, 2023

Mountain snowpacks act as natural water towers, storing winter precipitation until summer months when downstream water demand is greatest. We introduce a Snow Storage Ind

Mountain snowpacks act as natural water towers, storing winter precipitation until summer months when downstream water demand is greatest. We introduce a Snow Storage Index (SSI), representing the temporal phase difference between daily precipitation and surface water inputs—sum of rainfall and snowmelt into terrestrial systems—weighted by relative magnitudes. Different from snow water equivalent or snow fraction, the SSI represents the degree to which the snowpack delays the timing and magnitude of surface water inputs relative to precipitation, a fundamental component of how snow water storage influences the hydrologic cycle. In western North America, annual SSI has decreased (p 

Recent Scientific Contributions by the U.S. Geological Survey in the San Francisco Bay and Sacramento–San Joaquin Delta Estuary

U.S. Geological Survey (USGS) | January 26th, 2026

Recent strengthening of eastern Pacific ENSO in the last millennium paleorecord

American Association for the Advancement of Science (AAAS) | August 27th, 2026

The Pacific El Niño–Southern Oscillation (ENSO) generates climate extremes that endanger ecosystems, infrastructure, and human well-being worldwide. The response of th

The Pacific El Niño–Southern Oscillation (ENSO) generates climate extremes that endanger ecosystems, infrastructure, and human well-being worldwide. The response of this system to climate warming is poorly constrained, due both to data scarcity and uncertainties in climate models. The geochemistry of Galápagos coral skeletons across the past millennium reveals a large recent increase in interannual variability of sea surface temperature in the eastern equatorial Pacific compared to existing paleorecords that exceeds simulated natural variability. This increase parallels rising global temperature and results from stronger El Niño events. Central Pacific coral data also show increased variability, although less distinctly than in the Galápagos. Our results provide long-term context for understanding ENSO variability trends, with troubling implications for climate extremes.

Recharge Area Identification, Utilization, and Protection Resource Management Strategy

California Department of Water Resources (DWR) | April 29th, 2024

This resource management strategy (RMS) advances water supply augmentation, resilience, and equity in California by providing summaries of the state of knowledge, applica

This resource management strategy (RMS) advances water supply augmentation, resilience, and equity in California by providing summaries of the state of knowledge, applications, and available information and resources on recharge area identification, utilization, and protection.

Recharge Net Metering to Enhance Groundwater Sustainability

University of California, Berkeley (UC Berkeley) | April 2nd, 2018

Groundwater sustainability depends on balancing aquifer inflows and outflows. Extraction (pumping of groundwater, typically for human use) and recharge (inflow of

Groundwater sustainability depends on balancing aquifer inflows and outflows. Extraction (pumping of groundwater, typically for human use) and recharge (inflow of water to an aquifer from the land surface and streams) are central components of this water balance. Often, increasing demands for groundwater are exacer- bated by stresses on limited surface water supplies. Changes in land use and shifting climate can result in less infiltration of precipitation into the ground, reducing recharge. Increasing water scarcity has led to increased pumping, and in turn, unsustainable management of groundwater in many basins, resulting in depleted supplies, degraded water quality, and other impacts.