Conserving diverse freshwater ecosystems requires a variety of conservation approaches, at many different scales. We explore several strategies, including area-based conservation, local restoration, and wildlife reintroduction. For example, one project examines how state or national area-based conservation schemes can shift focus to specifically include freshwater ecosystems, providing climate, biodiversity, and societal benefits while also better protecting freshwater systems. Our recommendations for centering freshwater ecosystems are to 1) focus on watershed-scale conservation; and 2) consider five freshwater ecosystem priorities, including connectivity, watershed disturbance, flow alteration, water quality, and biodiversity. 

Another approach to freshwater conservation is to focus on small-scale local restoration projects. For example, we have worked on floodplain restoration in the Klamath River watershed in northern California, where hydropower development and high river water temperatures threaten juvenile salmonids. We show that human-made off-channel floodplain ponds provide cooler and more stable thermal refuge habitat for salmonids, illustrating the value of small-scale restoration in systems that are highly impacted by human development. 

Reintroducing a native wildlife species is a third strategy for conserving freshwater ecosystems. We study the reintroduction of the North American beaver (Castor canadensis) in California. Beavers are ecosystem engineers that could have both biodiversity and climate resilience (water storage and fire risk) benefits at the landscape scale. Our results show that after centuries of overutilization, considerable capacity for beaver dams remains throughout the California Sierra Nevada region. We also show that beavers have the potential to store significant surface water and create fire resilient landscapes throughout the region, illustrating how restoring a keystone species can benefit both ecosystems and society.

How could restoring rivers’ flow regimes (the typical pattern of how water flows through a watershed) also support the restoration of their ecological processes (e.g., the transfer of nutrients across a food web), while enriching cultural and recreational opportunities? We are researching the potential for flow-based restoration in the context of two Southern California rivers, the Los Angeles and the Santa Clara. Treated wastewater discharges (effluent), floodplain development, urban run-off, and dams have altered both rivers’ flow regimes, which historically had more distinctive flow variation between their dry and wet seasons and less flashy high flows. But while the L.A. River is among the most concrete-covered rivers in the region, and many of its surface flows do not currently connect to groundwater or its floodplains, the Santa Clara remains largely unchannelized, even as it faces increasing floodplain development. As the region grapples with the need to bolster its local water supplies and increase access to green space, we are exploring how restoring flows could help us achieve both aims.

We are studying flow-ecology relationships, asking how consistent our findings are across the sister watersheds. We conducted aquatic and terrestrial invertebrate surveys, plant surveys, and bird point counts at sites with a gradient of flow conditions along both rivers over three years (2021-2023). We are finding that changing flows will affect the rivers’ food webs differently based on the ecological communities that they support today. For instance, effluent discharges along the concrete-lined L.A. River create a perennial wetland habitat, which primarily supports aquatic-dependent bird species, whereas the Santa Clara River supports birds with a wider array of habitat preferences, including more riparian-dependent bird species that take advantage of its aquatic and riparian vegetation. We recognize that changes in flows have both ecological and social implications — and speak to our priorities as a society. With that in mind, we are in the process of interviewing people who work on and live near both rivers, learning about their perceptions of and priorities for flow-based restoration. By studying how flows currently relate to invertebrates, plants, birds, and people, we will make predictions about how changes in flows may affect them. Ultimately, we will recommend flow-based restoration approaches that can provide benefits across the region.