by Robin Meadows
California’s freshwater ecosystems―from springs and wetlands to rivers and estuaries―are in trouble and the warming world is hastening their decline. Fish and the wealth of other aquatic species that live in these habitats are increasingly vulnerable as freshwater flows shrink and water temperatures rise.
“Climate change is right on top of us, it’s really coming a lot faster than we expected,” says aquatic ecologist Ted Sommer, a fellow at the Public Policy Institute of California Water Policy Center and former lead scientist for California Department of Water Resources. “Many freshwater species could be extinct by the end of the century.”
Protecting the state’s freshwater biodiversity, especially in the face of climate change, can be a disheartening task. “It’s easy for people to get overwhelmed,” Sommer says.
To help make this task less daunting, Sommer led a team that identified tools for reversing the decline in freshwater species and ecosystems. The team presented their findings in a May 2024 report called Climate-Smart Tools to Protect California’s Freshwater Biodiversity.
Goals included giving resource managers and planners approaches they can use immediately, as well as sparking further innovation by scientists and engineers. “We came up with a toolbox of bold conservation solutions,” Sommer says. “Many are familiar and others are more at the science-fiction end.”
To learn more, Robin Meadows spoke with Sommer about tools that can be used right away, tools that are more conceptual but worth considering, and the need to think beyond conventional approaches to conserving freshwater ecosystems. This conversation has been edited for conciseness and clarity.
What’s in your toolbox and how did you organize it?
We looked for and asked colleagues for ideas, and then divided the toolbox into three main drawers: habitat support, species support, and contingency actions.
Habitat support: The top drawer of the toolbox contains actions likely to have ecosystem benefits that will help a lot of species. This includes conventional ideas like freshwater inflows and high quality habitat restoration as well as newer ideas.
There’s a new approach to restoration at the Salton Sea, which is undergoing rapid salinization as freshwater inflows diminish. Instead of trying to save it all, they’re restoring habitat and directing freshwater to the southwest corner. This way they’re securing at least part of it.
Invasive species control is another kind of habitat support, and innovative approaches include biocontrol―using natural enemies to suppress invasives―and robotics. The PixieDrone is a robot that targets aquatic weeds. We initially thought it was a cool sci-fi idea but to our amazement, people are already testing it in Lake Tahoe.
Species support: Climate change is going to force major shifts in where freshwater species can live and while habitat support is the highest priority, in a lot of cases it won’t happen fast enough. Then you need interventions to support individual species, and this is what’s in the middle drawer of the toolbox.
Salmon will need the higher, colder waters of their historical habitat, and dam removal would be great for that. But taking down the Klamath dams took 20 years, which is too long. The fish urgently need help to get past barriers. Winter-run chinook eggs, for example, are being reintroduced into the upper Sacramento River system. More experimental tools include fish cannons, which are long tubes with pumps that can move adult salmon up above dams.
Where the existing habitat is no longer suitable, we may need to move species beyond their historical ranges. Assisted migration was long used to stock lakes in the Sierra Nevada with native and non-native trout for fishing. A recent federal rule allows this technique to be considered for species conservation.
We also need to boost populations by preventing mortality or through supplementation. Examples include conservation hatcheries, which are lifeboats for introducing rare species like Delta smelt into the wild.
Another type of species support is assisted evolution. Given enough time, species will do it on their own. But climate change is moving so fast that interventions like special breeding programs may be needed. Coastal oysters are ecosystem engineers: oyster reefs protect shorelines against storms and provide habitat for other species. But little larval oysters don’t survive the warm temperatures and ocean acidification caused by climate change―it’s a one-two punch. People are now working to breed climate change-resilient oysters.
Other genetic interventions include hybridizing, which can boost survival in the face of a rapidly changing climate, and gene editing to knock out deleterious genes or add beneficial ones. Transgenics is in the science-fiction category and very controversial. We’re not advocating for it but we set out to be bold so scientists and engineers could consider and evaluate a broad range of options―there’s a lot of great innovation going on and we hope it inspires people.
Contingency actions: The bottom drawer of the toolbox contains actions to prepare for the worst-case scenario that we might lose species.
Examples include seed banks such as the Svalbard Global Seed Vault in Norway, which stores more than 1.2 million crop seeds from around the world at −18 °C, and the Frozen Zoo in San Diego, which stores eggs, sperm, and other tissues from nearly 1,000 kinds of animals at −196 °C.
These contingency actions have been a priority in terrestrial conservation for a long time. It’s not giving up, as some may think, it’s an ecosystem escape plan to make sure our freshwater legacy is preserved.
It’s already being done for salmon. Tissue archives of, for example, fin clips and muscle are being used right now to manage diversity in winter-run and spring-run chinook. That’s great but we have so many more freshwater species.
What else do you hope resource managers and planners will get out of your report? We focus too much on single species, too few ideas, and we’re not planning enough for the future.
Too often, resource managers latch onto one or two approaches, those with the least risk or those that are the most familiar. We’re pushing for a portfolio approach: we need to systematically go through watersheds and come up with a full list of options to protect species.
Ideally, we’ll also incorporate climate change into current planning processes. You really need to be thinking ahead to be ready for what’s coming. Instead of constantly looking back at what we’ve lost, we need to look forward at how to preserve the things we value.
For example, California’s Natural Community Conservation Plans, which provide regional protection for species and habitats, don’t necessarily focus as much as we think is necessary on climate change. They’re also often land-focused.
What’s next?
Team member Jennifer Harder, an environmental lawyer and professor at the University of the Pacific’s McGeorge School of Law, is leading the second part of the effort. She’s tasked with figuring out how to actually do what we recommend in this report. What kinds of laws, policies and programs do we need to support climate adaptation?
Things are so urgent we really can’t afford to wait. We need to fix degraded habitats ―and we know how to do this with tools like streamflow and restoration―and take climate actions now. If we don’t, we’re going to lose a lot of our freshwater biodiversity.
