The San Francisco Bay-Delta is literally threatened from all sides: rising sea levels from the ocean, disruptions to sediment supply from upstream, and within the Bay-Delta itself, development and other land use changes have left only a tiny fraction (5%) of marshland untouched.
Under climate change, coastal wetlands across the world, like the Bay-Delta, are disappearing. The rivers that feed coastal wetlands sediment which provide habitat for wildlife and form the structure of the ecosystem are transporting about a third less sediment, on average. Less sediment supply contributes to increased erosion of the ecosystem.
These delicate ecosystems provide several benefits to humans, such as protecting our shorelines, maintaining water quality, preventing damaging floods, and providing a peaceful place to recreate. In addition, they provide habitat for birds, fish, and other wildlife and play an important role in nutrient cycling, particularly carbon storage.
A recent study by scientists at the U.S. Geological Survey used historical streamflow and sediment data to calibrate models in order to predict what will happen to the Bay-Delta under varying levels of climate change.
In the future, California will continue to get about the same amount of rain, however, storms will be less frequent but more powerful. Therefore, streamflow will increase and the faster speed of the water will carry more sediment into the bay.
Rivers draining through the Sacramento Valley make their way to the Bay-Delta, and these waterways will likely experience higher peak streamflows. The new models projected that faster waters will carry 39 to 69 percent more sediment down to the Bay-Delta by 2100.
Unfortunately, the increased transport of sediment will bring a increased amount of pollutants. However, there are some silver linings to the projected sediment transport into the Bay-Delta:
Scientists think the higher sediment levels in the Bay-Delta will reduce impacts from sea level rise by raising the level of the Bay-Delta in concert with sea level rise, potentially reducing the amount of erosion exacerbated by rising oceans.
Turbidity, or how difficult it is to see through cloudy water, may increase, providing habitat for fish that can hide more easily from predators.
Ecosystems around the world face different challenges from climate change. While there are silver linings to the climate change impacts in the San Francisco Bay-Delta, this is not the case when we look at global climate change as a whole.
Understanding how local areas will experience climate change is key to effective natural resource management and to guide the best areas to invest our efforts in order to adapt to and mitigate climate change in our communities.