This study examines the historical hydrology and ecology of the Petaluma River watershed prior to major Euro-American modification, and analyzes landscape changes over the past two centuries. Synthesizing information from hundreds of archival documents, the research examines the historical form and function of wetland, riparian, and aquatic habitats and stream channels throughout the watershed, providing insights into habitat extent and distribution, streamflow and sediment dynamics, vegetation composition, wildlife support, and landscape change. Findings from this research can be used to help set restoration targets and to prioritize multi-benefit opportunities to restore wildlife habitat, enhance flood protection, increase groundwater recharge, and improve sediment management.

The Peninsula Watershed has been integral to the story of San Francisco's growth ever since the Gold Rush. The rapid influx of settlers to San Francisco during the Gold Rush spurred a sudden demand for a reliable water source, which led to the formation of the Spring Valley Water Works (later purchased by the Spring Valley Water Company [SVWC]) in 1858 (Hanson 2005 ). Over the subsequent 70 years, SVWC bought up large swaths of land on the Peninsula, and constructed a complex system of dams, tunnels, and pipes to capture and transport water to San Francisco. Within the Peninsula Watershed, this system includes the Crystal Springs and San Andreas reservoirs, located in the San Andreas Creek, Laguna Creek, and Upper San Mateo Creek basins along the San Andreas Fau The City of San Francisco purchased SVWC in 1930, and today the Peninsula Watershed, managed by the San Francisco Public Utilities Commission (SFPUC), continues to be a key source of water for San Francisco and for other communities in the South and East Bay. Despite the past 150 years of reservoir construction and other hydrologic modifications, the construction of transportation and utility corridors, and the large-scale suburban development that has occurred to the east, the Peninsula Watershed has remained largely undeveloped and is managed to protect water quality, water supply, wildlife habitat, and a range of other natural and cultural resources. The watershed supports some of the largest intact remnants of contiguous habitat in the region, including extensive oak woodlands, old-growth Douglas-fir forests, serpentine grasslands, chaparral, and coastal scrub. Over the past 250 years since Spanish explorers first set foot on the watershed, however, changes in disturbance regimes and other large-scale anthropogenic modifications, including fire suppression, homesteading, livestock grazing, agriculture, tree planting, introduction of plant pathogens, spread of invasive species, and climate change, have altered vegetation dynamics and changed the distribution and structure of vegetation communities throughout the watershed. The changes have raised many questions about the historical ecology of the watershed: What was the extent, distribution, and composition of terrestrial, riparian, and wetland habitats prior to Euro-American modification? How have vegetation distributions changed over the past two centuries, and what are the implications of those changes for species support? Are there remnant patches of relatively unmodified habitat present in the watershed, or areas that are currently in a state of recovery? Where are current habitat characteristics most similar to or different from historically documented conditions? How have key natural and anthropogenic disturbance regimes and processes changed over time? The Peninsula Watershed Historical Ecology Study aims to advance understanding of landscape conditions of the Peninsula Watershed prior to major Euro-American modification, and to provide insights into the nature and drivers of vegetation change since the first Spanish explorers set foot in the watershed 250 years ago. The primary goal of the research was to examine the historical extent, distribution, and composition of terrestrial vegetation types and their trajectories of change within the watershed. To the extent possible, research also addressed historical riparian, wetland, and estuarine habitats; hydrology and sediment dynamics; wildlife support; land use history; and a range of other topics.

This long-anticipated reference and sourcebook for CaliforniaÕs remarkable ecological abundance provides an integrated assessment of each major ecosystem typeÑits distribution, structure, function, and management. A comprehensive synthesis of our knowledge about this biologically diverse state, Ecosystems of California covers the state from oceans to mountaintops using multiple lenses: past and present, flora and fauna, aquatic and terrestrial, natural and managed. Each chapter evaluates natural processes for a specific ecosystem, describes drivers of change, and discusses how that ecosystem may be altered in the future. This book also explores the drivers of CaliforniaÕs ecological patterns and the history of the stateÕs various ecosystems, outlining how the challenges of climate change and invasive species and opportunities for regulation and stewardship could potentially affect the stateÕs ecosystems. The text explicitly incorporates both human impacts and conservation and restoration efforts and shows how ecosystems support human well-being. Edited by two esteemed ecosystem ecologists and with overviews by leading experts on each ecosystem, this definitive work will be indispensable for natural resource management and conservation professionals as well as for undergraduate or graduate students of CaliforniaÕs environment and curious naturalists.

One of California's most remarkable wetlands, Suisun Marsh is the largest tidal marsh on the West Coast and a major feature of the San Francisco Estuary. This productive and unique habitat supports endemic species, is a nursery for native fishes, and is a vital link for migratory waterfowl. The 6,000-year-old marsh has been affected by human activity, and humans will continue to have significant impacts on the marsh as the sea level rises and cultural values shift in the century ahead. This study includes in-depth information about the ecological and human history of Suisun Marsh, its abiotic and biotic characteristics, agents of ecological change, and alternative futures facing this ecosystem.

The resilience of San Francisco Bay shore habitats, such as tidal marshes and mudflats, is essential to all who live in the Bay Area. Tidal marshes and tidal flats (also known as mudflats) are key components of the shore habitats, collectively called baylands, which protect billions of dollars of bay-front housing and infrastructure (including neighborhoods, business parks, highways, sewage treatment plants, and landfills). They purify the Bay's water, support endangered wildlife, nurture fisheries, and provide people access to nature within the urban environment. Bay Area residents showed their commitment to restoring these critical habitats when they voted for a property tax to pay for large-scale tidal marsh restoration. However, climate change poses a great threat, because there may not be enough natural sediment supply for tidal marshes and mudflats to gain elevation fast enough to keep pace with sea-level rise. This report analyses current data and climate projections to determine how much natural sediment may be available for tidal marshes and mudflats and how much supplemental sediment may be needed under different future scenarios. These sediment supply and demand estimates are combined with scientific knowledge of natural physical and biological processes to offer a strategy for sediment delivery that will allow these wetlands to survive a changing climate and provide benefits to people and nature for many decades to come. The approach developed in this report may also be useful beyond San Francisco Bay because shoreline protection, flood risk-management, and looming sediment deficits are common issues facing coastal communities around the world.