RENO, Nev. — The Proceedings of the National Academy of Sciences (PNAS) has curated a special journal issue to discuss climate change adaptability in California. Researchers from the University of California, Berkeley, the University of Nevada, Reno and the Pacific Institute contributed a scientific perspective on the challenges and opportunities faced by California’s freshwater ecosystems. The researchers proposed a large-scale monitoring and modeling network as well as inclusive collaborations to facilitate evidence-based policy aimed at enhancing resiliency to climate change.

“California has the fifth largest economy in the world and supports many unique ecosystems, so we need to focus on sustaining the waters of California, from rivers and estuaries to lakes and groundwater,” Sudeep Chandra, professor of biology at the University of Nevada, Reno and coauthor on the paper, said.

The perspective article comes just before the annual Lake Tahoe Summit, an annual forum where policymakers, scientists and community stakeholders discuss how to preserve the lake. The summit theme this year is “Connecting Tahoe: Investing in Transit, Trails, and Technology for the Future.”

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Agriculture and tourism are among important contributing factors to California’s economy. Tourism hot spots in the state include Lake Tahoe, one of the clearest lakes in the world, and other mountain ecosystems. These economic engines inherently rely on the stability and sustainability of aquatic ecosystems. The types of ecosystems vary widely across the state, some more heavily impacted by humans, and others less impacted. Comparing impacted and intact ecosystems can provide greater understanding of how they respond to change, and how to exploit the natural systems for increased resiliency. Modeling how these different ecosystems respond to future changes depends on how much they have been altered.

Different types of ecosystems face unique threats

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Ecosystems heavily impacted include California’s Central Valley, known as the breadbasket of the world due to its agricultural outputs. The Central Valley pulls water from all over the state to irrigate produce on land once largely covered by wetlands. Scientists are finding wetlands to be incredibly useful landscapes for mitigating dangers posed by climate change (such as extreme flooding). When wetlands were replaced with agriculture, many species native to the region lost their habitat, and climate resilience was diminished. Inland wetlands can be lost due to groundwater pumping. These ecosystems are complex and opportunities moving forward to adapt to a changing climate need to harness the information available and develop a process-based understanding of ecological function and services.

Ecosystems considered less impacted include rivers in California’s North Coast Range and the state’s alpine lakes. Models reflect these ecosystems relatively well as they were in the past, but with changes in snowpack, temperature variability, groundwater storage and other systems, the models will quickly become outdated and unrealistic.

California’s widely ranging ecosystems, both natural and altered, require small-scale models to adequately reflect how climate will impact the state’s economy. These models, the researchers say, should consider how landscape, chemical, biological and physical processes taking place in the region both impact and are impacted by the effects of climate change. A strong example of modeling needs lies in the Sierra Nevada.

Lake Tahoe’s basin faced drought for three years, and in 2022-2023 the basin received one of the highest snowpacks on record. Much of that snow fell on landscapes significantly altered by the Caldor Fire, which burned through the region in 2022. These landscape interactions will have a strong impact on Lake Tahoe’s famed clarity, which helps drive the $5.1 billion tourist economy in the region. In just under 60 years, the lake’s clarity has decreased by ten meters. These physical and chemical changes, as well as changing snowmelt rates, will also impact the lake’s biology. Models should consider not only how one species might be affected by regional effects of climate change, but how that species’ adaptability will impact other species, necessitating a full ecological framework.

“The paper illustrates with several examples that while shifting water flow and temperatures regimes will drive change in freshwater ecosystems, the specific outcomes strongly depend on the ecological interactions of organisms within particular ecosystems, whether it be a frog and potential parasites, or salmon and their prey, predators, and competitors,” Mary Power, lead author on the article and professor at the University of California (UC), Berkeley, said.

Researchers call for improved models and increased collaborations

To improve understanding and create a more resilient California, the scientists recommend predictive mapping, which uses experimental results with natural variables to make inferences about how a variety of impacts from climate change might affect local ecology. In some instances, predictive mapping produced surprising results, indicating that while most ecological theory is useful, there are nuances in ecosystems that can lead to different-than-anticipated results.

“We now rely on regional and global climate models based on decades of observations for both forecasting the weather next week and the future threats of extreme heat events, droughts, intense precipitation, and flooding,” William Dietrich, study coauthor and professor at UC Berkeley, added. “There needs to be a comparable effort to develop freshwater ecosystem models, driven by observations, that can build on climate model forecasts to anticipate and ideally prevent ecosystem decline and, in fact, build resilience to anticipated climate changes.”

Many of the case studies referenced in the article were conducted in the University of California Natural Reserve System, which is earmarked for long-term freshwater ecosystem research with established field stations.

“These spaces are critical to developing models for how our ecosystems will evolve and adapt with climate change,” Power said. “With collective, intentional action, we can get a clear picture of what is happening in our ecosystems, and what we can do to help them adapt.”

Alongside robust models, the researchers emphasized the need for large-scale collaborations.

“We need collaborations across government agencies, universities, tribes, research institutes, consultants and non-governmental organizations to develop sufficient understanding of freshwater ecosystems,” Dietrich said. “Then, we can build models that can anticipate the effects of climate change in the coming decades to build management strategies that support ecosystem resilience.”

Equally important to progress in water sustainability are long-term field studies, policy development and education and training of current and future water experts, like the training taking place at the University of Nevada, Reno’s Global Water Center. Chandra, who co-founded and directs the center, has seen many early career faculty in the center perform comprehensive studies of aquatic systems.

“Work at the Global Water Center, which includes faculty with broad-ranging research interests, has already shown that interdisciplinary research provides unique perspectives and insights which serve to piece together a fuller picture of ecosystem inputs and outputs,” Chandra said.