Well what do you know? It turns out wetlands are really important! Just ask Katrina. Especially the tidal zones in between salt and freshwater like where our beavers lived. Gosh who would have guessed?

A watershed study for wetland restoration

Where rivers meet oceans, each cycle of the tide moves water in and out of estuaries. The mixing and mingling of fresh and briny water, combined with seasonal weather, creates a unique environment for ecosystems in coastal estuaries and upstream tidal rivers.

The framework is described in “Ecohydrology of wetland plant communities along an estuarine to tidal river gradient,” which appeared September 18 in the Ecological Society of America’s open-access journal Ecosphere. The research is the latest in a series of regional-scale studies supported by the Bonneville Power Administration and U.S. Army Corps of Engineers, Portland District, which are implementing a program to reconnect and restore wetlands on the Columbia River floodplain.

You know where our beavers lived right? It was right on the border between the salty strait and the fresh creek. Literally right on the in between place. Are those places important?

Like giant sponges, wetlands serve key environmental functions, such as controlling flooding, storing carbon, and filtering pollution. Wetland habitats also provide protection and food for birds, fish, and mammals. For example, tiny salmon nibble along the shores of the Columbia River, growing and gaining strength on their downriver journey to the Pacific Ocean.

But Diefenderfer said that these important coastal ecosystems often go unnoticed or are viewed as wastelands.

Sure, that’s the truth. Their unsafe to build on so they don’t make people any money. Cities either ignore those spaces or bring in topsoil to make it less responsive to tides.

The long-term research effort, a focus of PNNL’s Coastal Ecosystems Research team, allowed scientists to record plant responses in low-, medium-, and high-flow years. Results showed that plant species varied across elevations within wetlands and along the river. The variations depended on the distance from salt and tides at the coast, and the volume of river flow below the head of tide.

The team also found that wetness—or inundation—largely determined plant communities and resistance to non-native species. Nearest the Pacific Ocean, salinity kept non-native species from taking hold. Just upriver, in the strongly tidal but freshwater zone, plant species diversity was highest—an indicator of resilience in the tidal wetlands.

Huh. Martinez sure has a lot of Arundo near the salty parts. But I guess the strait isn’t pure ocean, so maybe it doesn’t count. The interesting part to me is that the richest part of the wetland is where our beavers chose to live. Chicken or egg?

Farther upriver, changes in daily, seasonal, and yearly wetting and drying cycles increased invasion by non-native species. These cycles also decreased aquatic plant diversity and other vegetative cover. On average, the quality of plant communities significantly improved closer to the ocean.

Well, sure. Plants in more saline areas were less vulnerable to non-native invasion because it’s harder to thrive on the edge. And the more drought we experience the less fresh water flows into these areas and the more saline everything becomes. Hmm, Resilient plants do better I guess with climate change.

And everyone does better with more wetlands. Gosh it’s too bad there’s not some natural way to make more wetlands on a larger scale.