Wetlands on the Edge

By Andrew L. Rypel

Fig. 1. Coastal wetlands are the most valuable type of ecosystem on Earth. Photo showing the Bayland Nature Preserve near Palo Alto, California. Credit: Frank Chen/Getty Images.

It’s really easy to overlook and undervalue wetlands. Some are small or just don’t look very important. Others are enormous, and cause flooding issues for homeowners and growers. Some might even think wetlands are gross, worry about mosquitos and vector borne illness, or have never experienced what it’s like to be close to or inside of one. It’s uncommon to see a home or store positioned on a wetland (usually because it was drained), so perhaps they can also appear to be taking up valuable real estate better utilized for ‘human needs’.

Naturally, wetlands require water, which means they compete with humans for the acre-feet we so often discuss in California water. Yet according to Constanza et al. 1997, ecosystem services for wetlands, compared to all other ecosystem types, are the most valuable on Earth. On average, estuarine wetlands deliver $43,486/ha/y in services (adjusted to 2023), followed closely by freshwater wetlands at $37,292/ha/y. Historically, there were alot of both types of wetlands in California – somewhere in the neighborhood of 4 million acres, but at least 95% of these habitats have been eliminated. Thus, widespread loss in wetlands, both in California and at broader scales, signal huge misunderstandings regarding their importance. Failure to understand and protect wetlands dovetails with our twin inability to protect freshwater biodiversity, so much of which relies directly on these habitats (Rypel 2023).

Wetlands provide countless benefits for people and ecosystems. They are a giant and natural filtration system that not only improves water quality (Gilliam 1994; Verhoeven et al. 2006), but also water quantities, primarily via groundwater recharge (Van der Kamp and Hayashi 1998). Wetlands trap sediments, remove excess nutrients like nitrogen and phosphorus, and detoxifies other chemicals (Duffy and Kahara 2011; Mitsch et al. 2015). And of course, wetland ecosystems promote biodiversity at all scales (Denny 1994). This is especially true in California where most of our fragile biodiversity relies explicitly on wetlands (Fig.1, Brinson and Malvárez 2002; Leibowitz 2003; Zedler 1991; Katz et al. 2013). Alpine lakes and mountain meadows in the Sierra Nevada host native frog, toad, fish and salamander populations, along with native sedges, grasses, mosses, trees and flowering wetland plants (Fig. 2, Knapp et al. 2007; Parisek 2023). Wetlands are especially crucial in the Central Valley – a literal well of freshwater biodiversity in California. Here, floodplains are the key (Sommer et al. 2001; Katz et al. 2017; Jeffres et al. 2020; Rypel et al. 2022). We increasingly understand that these habitats once served as overwintering habitats for migratory birds (Bird et al. 2001; Elphick et al. 2010), and as rearing habitats for juvenile salmonids and other native fishes of the Central Valley (Oppermann et al. 2017). Herpetofauna, like the giant garter snake, still require this exact floodplain habitat that is now mostly destroyed (Nguyen et al. 2023); hence the snake is nearly destroyed. These same floodplains, managed the right way, protect our communities from floods, and can even be used during dry seasons for agriculture (Holmes et al. 2021; Torres et al. 2022). Increasingly, we will also turn to wetland rehabilitation as part of climate change adaptation and mitigation strategies, especially in the mountains as an effort to slow runoff that incresingly will fall as rain rather than snow. This is one reason why beavers, a species once broadly maligned, now are generating interest as a nature-based solution for adapting to climate change, and creating and enlarging the footprint of wetlands (Rypel 2022).

Fig. 2. Camassia quamash (Pursh). Photo credit: William & Wilma Follette 1992. Western Wetland Flora: Field Office Guide to Plant Species.

Yet not all wetlands are equal in terms of conservation impact (Barik et al. 2022). Therefore, a major challenge for conservation science will be prioritizing ecosystems and watersheds that provide ‘bang for the buck’. NGOs often excel at these kinds of tasks, and can leverage prioritization frameworks to translate science into action by restoring wetlands, bringing down deadbeat dams, lobbying on behalf of beavers or engaging in other positive activities. Yet to my knowledge, there is no statewide tool for prioritizing conservation management of California wetlands. Tools and working groups exist for certain kinds of wetland ecosystems (e.g. mountain meadows, floodplains etc), but a statewide effort largely remains lacking. This is unfortunate because it will directly hinder the ability for an important effort like the California 30×30 initiative to gain true success. For example, what good is conservation of 30% of California, if the land is of the wrong type (i.e., not enough wetlands)?

I recently reacquainted myself with some of the excellent watershed conservation efforts in Minnesota (Jacobson et al. 2016). Their effort is focused more on forest soils than wetlands per se, but I think it is a good example and heuristic for how to build a statewide watershed conservation program. The MN watershed program seems to be especially targeted at private forests that are at risk of development. Tacit in the approach is a broader expansion of the notion of wetlands – that traditional wetlands alone probably cannot remove enough sediments and nutrients when exposed to intensive development and agriculture. What is unique and exceptional to me about this work is that 1) it is statewide in scope; and 2) it focuses on deliberate science-based targets. For example, researchers observe that after 25% agricultural and urban land use, major increases in phosphorus are observed in waterways, substantially increasing the risk for harmful algal blooms, fish kills and poor freshwater habitat. Therefore, a good goal for watersheds in Minnesota is 75% protection. Furthermore, they developed a prioritization tool (Fig. 3). The value of the tool is that watersheds meeting the threshold can easily be identified, along with those near the benchmark, and those far away. Essentially, you can easily pick out watersheds where additional protection or restoration would have the most positive impact.

Fig. 3. Example of a statewide conservation prioritization schema. In Minnesota, many watersheds in the northern part of the state are well-protected. Watersheds in the southern part of the state are highly developed and can only hope for partial restoration. Watersheds in the middle and near north part of the state appear to have the highest odds for full restoration. From Jacobson et al. 2016.

You might be looking at this example thinking, “Well, those thresholds are totally unrealistic in California. Maybe in Minnesota, but certainly not California.” Yes, perhaps a 75% threshold is unrealistic in parts of California, but i) This is also true in Minnesota (see southern region of Fig. 3B); ii) We don’t know what a threshold might be in California. And iii) From a policy perspective, a California threshold goal can be whatever we collectively make it. California also has the benefit of agroecosystems, some of which provide surrogate ecological benefits. I would contend, that at this point, we know enough about the surrogate ecological benefits of rice fields (Katz et al. 2017; Jeffres et al. 2020; Holmes et al. 2021; Rypel et al. 2022), that under proper management, these habitats might not count against a wetland protection goal, but rather towards it. Similar incentive programs for waterfowl and migratory birds have existed for years, primarily through NRCS practice standards. Ultimately, the broader point is that all these details and California idiosyncrasies can be worked out using a parallel system adapted to be California-centric. And having such a tool will only increase our ability to be strategic and wise with limited funds and time. Other states have also put forward statewide wetland conservation strategies/tools, so there are many models from which to pick, examine, study and even blend.

During spring of this year, a US Supreme Court ruling, in Sackett vs EPA, dramatically reduced federal protections for wetlands, especially small wetlands throughout the US. The ruling made less noise in California because our state has more stringent laws that provide a backstop to the federal change. These enhanced California laws are the product federal, state, and local agency staff that engaged with wetland science 10-20 years prior, and foresaw the need to safe guard against a shifting and uncertain legal focus of the Clean Water Act in California. However, the new nationwide impacts of the Sackett decision were on full display this last week when the US EPA issued their final rule in response to Sackett, functionally amending the definition of protected waters of the US. The net impact is that wide swaths of wetlands previously protected are not protected anymore, and it will be up to the states to do the hard work of figuring out how to step in. Many of them won’t. I worry especially about biodiversity hotspots in regions that have a poor history of freshwater conservation and lots of valuable wetland real estate (e.g., southeastern USA). Over time, the ruling will brutally show how wetlands remain under constant jeopardy, and have now been sent on a march to the absolute edge and beyond. Despite their ecological and economic values, it simply remains far too expedient to harm, reduce and eliminate wetlands. But understanding is growing, and I see signs (e.g., in the movement to protect and recover beavers) that people and communities are standing up. Indeed we must all learn and teach to better understand wetlands, and rescue our valuable swamps back from the edge!

I wrote this blog mostly while sitting in front of this wetland. Photo by the author.

Further Reading:

Barik, S., G. K. Saha, and S. Mazumdar. 2022. Conservation prioritization through combined approach of umbrella species selection, occupancy estimation, habitat suitability and connectivity analysis of kingfisher: A study from an internationally important wetland complex (Ramsar site) in India. Ecological Informatics 72:101833.

Bird, J., G. Pettygrove, and J. M. Eadie. 2000. The impact of waterfowl foraging on the decomposition of rice straw: mutual benefits for rice growers and waterfowl. Journal of Applied Ecology 37:728-741.

Brinson, M. M., and A. I. Malvárez. 2002. Temperate freshwater wetlands: types, status, and threats. Environmental Conservation 29:115-133.

Costanza, R., R. d’Arge, R. De Groot, S. Farber, M. Grasso, B. Hannon, K. Limburg, S. Naeem, R. V. O’Neill, and J. Paruelo. 1997. The value of the world’s ecosystem services and natural capital. Nature 387:253-260.

Denny, P. 1994. Biodiversity and wetlands. Wetlands Ecology and Management 3:55-611.

Duffy, W. G., and S. N. Kahara. 2011. Wetland ecosystem services in California’s Central Valley and implications for the Wetland Reserve Program. Ecological Applications 21:S128-S134.

Elphick, C. S., O. Taft, and P. M. Lourenço. 2010. Management of rice fields for birds during the non-growing season. Waterbirds 33:181-192.

Gilliam, J. 1994. Riparian wetlands and water quality. Journal of Environmental Quality 23:896-900.

Holmes, E. J., P. Saffarinia, A. L. Rypel, M. N. Bell-Tilcock, J. V. Katz, and C. A. Jeffres. 2021. Reconciling fish and farms: Methods for managing California rice fields as salmon habitat. PLoS ONE 16:e0237686.

Jacobson, P. C., T. K. Cross, D. L. Dustin, and M. Duval. 2016. A fish habitat conservation framework for Minnesota lakes. Fisheries 41:302-317.

Jeffres, C. A., E. J. Holmes, T. R. Sommer, and J. V. Katz. 2020. Detrital food web contributes to aquatic ecosystem productivity and rapid salmon growth in a managed floodplain. PloS ONE 15:e0216019.

Katz, J., P. B. Moyle, R. M. Quiñones, J. Israel, and S. Purdy. 2013. Impending extinction of salmon, steelhead, and trout (Salmonidae) in California. Environmental Biology of Fishes 96:1169-1186.

Katz, J. V., C. Jeffres, J. L. Conrad, T. R. Sommer, J. Martinez, S. Brumbaugh, N. Corline, and P. B. Moyle. 2017. Floodplain farm fields provide novel rearing habitat for Chinook salmon. PloS ONE 12:e0177409.

Knapp, R. A., D. M. Boiano, and V. T. Vredenburg. 2007. Removal of nonnative fish results in population expansion of a declining amphibian (mountain yellow-legged frog, Rana muscosa). Biological Conservation 135:11-20.

Leibowitz, S. G. 2003. Isolated wetlands and their functions: an ecological perspective. Wetlands 23:517-531.

Mitsch, W. J., B. Bernal, and M. E. Hernandez. 2015. Ecosystem services of wetlands. Pages 1-4. Taylor & Francis.

Nguyen, A. M., B. D. Todd, and B. J. Halstead. 2023. Survival and establishment of captive‐reared and translocated giant gartersnakes after release. The Journal of Wildlife Management 87:e22374.

Opperman, J. J., P. B. Moyle, E. W. Larsen, J. L. Florsheim, and A. D. Manfree. 2017. Floodplains: Processes and management for ecosystem services. University of California Press.

Parisek, C.A. 2023. A “peak” into California’s alpine lakes and their food webs. https://californiawaterblog.com/2023/08/06/a-peak-into-californias-alpine-lakes-and-their-food-webs/

Rypel, A.L., P.B. Moyle, and J. Lund. 2021. A swiss cheese model for fish conservation in California. https://californiawaterblog.com/2021/01/24/a-swiss-cheese-model-for-fish-conservation-in-california/

Rypel, A.L., C.A. Parisek, J. Lund, A. Willis, P.B. Moyle, Yarnell, S., and K. Börk. 2020. What’s the dam problem with deadbeat dams?, https://californiawaterblog.com/2023/05/28/whats-the-dam-problem-with-deadbeat-dams/

Rypel, A.L. 2022. Nature has solutions…What are they? And why do they matter? https://californiawaterblog.com/2022/03/27/nature-has-solutions-what-are-they-and-why-do-they-matter/

Rypel, A.L., D.J. Alcott, P. Buttner, A. Wampler, J. Colby, P. Saffarinia. N. Fangue, and C.A. Jeffres. 2022. Rice and salmon, what a match! https://californiawaterblog.com/2022/02/13/rice-salmon-what-a-match/

Rypel, A.L. 2023. Facing the dragon: California’s nasty ecological debts. https://californiawaterblog.com/2023/06/11/facing-the-dragon-californias-nasty-ecological-debts/

Sommer, T., B. Harrell, M. Nobriga, R. Brown, P. Moyle, W. Kimmerer, and L. Schemel. 2001. California’s Yolo Bypass: Evidence that flood control can be compatible with fisheries, wetlands, wildlife, and agriculture. Fisheries 26:6-16.

Torres, F., M. Tilcock, A. Chu, and S. Yarnell. Five “F”unctions of the Central Valley floodplainhttps://californiawaterblog.com/2022/05/08/five-functions-of-the-central-valley-floodplain/

Van der Kamp, G., and M. Hayashi. 1998. The groundwater recharge function of small wetlands in the semi-arid northern prairies. Great Plains Research:39-56.

Verhoeven, J. T., B. Arheimer, C. Yin, and M. M. Hefting. 2006. Regional and global concerns over wetlands and water quality. Trends in Ecology & Evolution 21:96-103.

Zedler, J. B. 1991. The challenge of protecting endangered species habitat along the southern California coast. Coastal Management 19:35-53.







About Andrew Rypel

Andrew L. Rypel is a Professor and the Peter B. Moyle and California Trout Chair of coldwater fish ecology at the University of California, Davis. He is a faculty member in the Department of Wildlife, Fish & Conservation Biology and Director of the Center for Watershed Sciences.
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2 Responses to Wetlands on the Edge

  1. I would like to commend Professor Rypel for stepping forward on a political issue important to freshwater fish ecology.

  2. Erinne Yoo says:

    The every effort to conserve our wetlands and biodiversity are ridiculed by the California Forever project. The run-off from the new city filled with 100,000 residents flowing into the Delta rivers?

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