Freshwater flows in the Estuary have been highly altered, causing reductions in inter-annual and seasonal variability, and peak-flows. Freshwater flows into the Estuary in recent years reflect chronic artificial drought conditions, in sharp contrast to unimpaired flows.
Tidal marsh acreage throughout the Estuary has declined significantly from the historical amount, but restoration efforts are bringing back this critical ecosystem and associated benefits. Projects in the Bay are making extensive contributions to tidal marsh area, while efforts in the Delta are beginning to make progress towards regional goals.
The condition of fish communities varies across the Estuary. In the lower Estuary, fish communities are abundant, diverse, and dominated by native species. However, in the brackish and freshwater upper Estuary, native fish communities are in poor condition. Based on long-term monitoring data, native fish communities across the Bay are declining. In San Francisco and San Pablo Bays, this long-term data set is from sampling only the offshore areas of the Bay and may not reflect benefits to fish populations from recent wetland restoration.
The frequency, magnitude, and duration of floodplain inundation in both the Bay and the Delta are too low to support healthy estuarine habitats and sustain important ecological processes. While conditions have been variable over time, they have, in general, remained poor in the Delta and have declined in the Bay.
In both the Bay and Delta, total and per-capita urban water use have declined over the last several decades, despite growing populations. More efficient urban water use means that both regions met and exceeded benchmarks for per-capita use and drought-reduction targets. The regions have modestly increased water use since the end of the drought but still maintained improvements over their 2020 benchmarks for reductions in per-capita use.
Significant portions of previously tidal areas in the Bay and Delta have been diked off and disconnected from tidal action to accommodate agriculture, urban development, duck ponds, salt ponds, and a diverse set of other land uses. The low elevation of these areas places them at increased risk of flooding as sea level rises and intense rainstorms become more common. In addition, many of these former tidal marshes and mudflats have subsided significantly below sea level as a result of sediment oxidation and compaction. Subsidence and these accompanying processes exacerbate flood risk, contribute to greenhouse gas emissions, and reduce the potential for restoring important intertidal habitat types.
Levees and seawalls line many miles of the shorelines of San Francisco Bay and the Sacramento-San Joaquin Delta. By hardening the Estuary’s once soft and absorbent shores, early developers intended to keep people and property safe from flooding. These engineered structures do not provide good habitat for native species, however. Nor are they designed to accommodate the kind of flooding projected for our future, flooding produced by a combination of rapid sea level rise, higher groundwater tables, storm surge, and more rainfall over shorter periods.
Open spaces within urban areas provide a diverse set of benefits for wild animals, plants, and people that live nearby. Green spaces decrease urban runoff, improve downstream water quality, and provide habitat for native wildlife, while also benefiting human health and wellbeing. Urban parks improve local air quality and reduce local temperatures, contributing to lowered rates of childhood asthma and heat-related deaths in nearby areas. Exposure to urban parks is also associated with improved mood, increased physical activity, lower heart rate, and additional human health benefits.
The results are alarming for our state’s future: an estimated four to five feet of sea level rise and loss of one to two-thirds of Southern California beaches by 2100, a 50 percent increase in wildfires over 25,000 acres, stronger and longer heat waves, and infrastructure like airports, wastewater treatment plants, rail and roadways increasingly likely to suffer flooding.