By Andrew L. Rypel
In the coming weeks, fall-run Chinook salmon (Oncorhynchus tshawytscha) will appear in Putah Creek again to spawn. The fact that any salmon spawn in Putah Creek is a small miracle, and testimony to the resilience of salmon and a small army of people that worked tirelessly to restore and care for the ecosystem. UC Davis Emeritus Distinguished Professor Peter B. Moyle was one of the linchpins in making this happen. Field data from the classes he taught at UC Davis were used in the legal proceedings to improve the creek in the late 1990s, partly because no one else studied the stream. Like many California rivers, flows are an organizing ecological factor, driving the assembly of native and non-native fishes in Putah Creek (Marchetti and Moyle 2001). Since the Putah Creek Accord in 2000, several changes to water management have proved beneficial to native fishes (Keirnan et al. 2012, Jacinto 2020). These include increased spring flows, reduced water temperatures, increased summer flows to prevent the creek from drying, and fall attraction flows for migratory native fishes, like salmon. There was hope at that time that collectively these actions might one day bring anadromous salmon back to the system. These hopes were realized in fall 2013, when <10 adult Chinook salmon were found in the stream. Most of the recolonizing salmon turned out to be strays from California hatchery efforts (Willmes et al. 2020). Numbers increased in most years since (Chapman et al. 2018), until an unfortunate fish kill last year coincided with an usual early fall storm. One step forward and two steps back. Actions are being taken this year and future years to prevent a repeat and put the Putah Creek salmon population back on the growth trajectory. But, recovery is clearly not rapid.
Ecosystems are unsurprisingly highly complex and dynamic. Disturbances are common, and interactions among species can be intense and important (Winemiller 1989). Perhaps for these reasons, populations express tremendous heterogeneity in space and time (Rypel 2021; Blog digesting this paper). On top of this are myriad ways humans impact ecosystems: climate change, habitat loss and fragmentation, invasive species, pollution, overfishing, and genetic manipulation. It’s no wonder nature is hurting globally. This week, World Wildlife Fund (WWF) released a sobering report highlighting the perilous state of biodiversity on Earth. The report emphasized the decline of freshwater biodiversity. And although there are issues with precision of numbers presented in the report, the overriding signal of biodiversity decline is unmistakable, especially in freshwater. We are impacting freshwater environments on scales never seen before, and the losses continue to mount.
It’s easy to ‘get down’ about Earth’s sad news, and even be paralyzed by it. But many bright spots also exist. At the university, daily, I see large bunches of young people absolutely determined to help protect and recover our Planet, including its frail biodiversity. There are growing examples of ecosystem rehabilitations that actually work, species coming off the Endangered Species Act, and examples using Indigenous knowledge showing how management can be protective, inclusive, and honorable (Morin et al. 2021). Quietly, the largest dam removal in US history is being prepared in California and Oregon. This effort is vital to Indigenous peoples of the Klamath River whose families have depended on the river for generations, and is an opportunity for new partnerships. While conservation success stories are more rarely identified in the media, when one looks closely, they are there. And there is a motif to these stories, not always, but generally.
The success stories are not overnight. They are usually built the hard way – through collaboration, relationships, years of investment, long-term monitoring, and of course, sound science. Any small survey of the success stories clearly shows that nature is often ready to come back – when we give it a chance. We saw glimpses of this dynamic during Covid lockdowns, when animal behaviors quickly started to shift. Yet fuller or even modest ecological recoveries can take years, decades, and maybe longer. Several examples from my own work support this notion. Spring-run Chinook salmon were reintroduced into the San Joaquin River in 2013 and 2014; and while there have been successes, there is still a long way to go, and water quantity remains a principal limiting factor in recovery. On the other side of the Delta, we are actively trying to use agricultural floodplains (rice fields) to mimic natural floodplains. And again, while there have been some successes, and much promise for the future, there remains a road ahead, with much science still needed to work the whole thing out. In some cases, the need to take a long view is necessary just from a life-history standpoint. For example, recovering long-lived sturgeon, redwood or elephant populations will necessarily take decades given their low replacement rates. Further, the sheer intensity of impacts humans are delivering to Earth cannot be underestimated (Vitousek et al. 1999; Folke 2021). And because it took us a long time to get into these messes, it may take equally long or longer to dig back out. In some cases, ecosystems may never come back the same. Just as people need time to heal from an injury or traumatic event, so too, ecosystems need our patience when we begin working to bring them back from the brink, or even the damned.
Persistence may be equally important. Persistence is needed in paying attention to detect, understand, and address complex problems. Persistence is necessary for adapting to changes in socioecological conditions, which are often exceedingly complex. Persistence is important for navigating our political system, sometimes multiple times. Political priorities shift because of changes to political leadership, budgets, events, and crises du jour. Persistence to follow through over the long haul often separates successful from less successful recovery projects. And because persistence is in many ways a personality trait, sustained long-term efforts require long-term commitments from people – all of us – to ensure that ecological recoveries reach their full potential. This is hard work, and I’m not sure everyone who contributes to these efforts is ever fairly recognized for their important labor.
Walking along Putah Creek now, it is easy to take for granted all the work needed to get to this point. Those involved over the long haul see this. It took 13 years for Chinook salmon to find Putah Creek again. It took another 10 to get the numbers back up. And it might take at least another 10 to really start getting it right. That’s 33 years in the right direction – a career for someone. And yet still more work remains. Sometimes, we tell ourselves or our loved ones to be patient and give one another grace. This same way of thinking is probably true with nature, and us, especially as we heal.
Chapman, E., E. Jacinto, and P. Moyle. Habitat restoration for Chinook salmon in Putah Creek: a success story, https://californiawaterblog.com/2018/05/13/habitat-restoration-for-chinook-salmon-in-putah-creek-a-success-story/
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