Here's a piece I wrote for the Living Shorelines blog about a genus of sedges deployed on our 2.0 wetland biofilters, edited slightly to fit the context of this platform!
The two Carex species planted in our 2.0 wetland biofilters this year are Carex lyngbyei, or Lyngbye's sedge, and Carex obnupta, or slough sedge. To the casual observer, these species are almost indistinguishable from one another—Lyngbye's sedge seems to appear slightly lighter green in color than slough sedge, but both generally appear in a cooler, blue-green tone as compared to some of the more yellow-green species on our barges. Throughout our field season, we also noticed that Lyngbye's sedge grew taller than slough sedge, although this isn't necessarily a standard difference between the two species.
Side-by-side comparison: Lyngbye's sedge, on the right, grew slightly taller than slough sedge
The similarities don't end at appearances—both Lyngbye's sedge and slough sedge are key native wetland plants with a preference for freshwater and estuarine habitats, or habitats where a freshwater body of water empties out into a saltwater body. These two Carex species like to grow along shorelines or in tidal floodplains, where they might be found respectively in narrow bands or extensive marsh flats.
Lyngbye's sedge and slough sedge are superstars within these ecological communities: their ability to provide erosion control and streambank stabilization along shorelines benefits a wide variety of other organisms. Where Carex species grow abundantly, we might observe some of the following physical changes in the environment: preservation of river meander patterns, creation of a shallow plain where sediment is deposited, stormwater abatement, and a mixing zone for fresh and saltwater. These changes can create a more stable and diverse habitat for other wetland organisms, preventing nutrient loss and maintaining a salinity gradient in the water.
The sedges themselves also serve as an important source of food, shelter, and nutrients, which can then support all kinds of wildlife. Waterfowl, like ducks, will consume sedge seeds, simultaneously relying on the tall leaves for shelter. Fish and other aquatic organisms also shelter in Carex stands, which then attracts predators like eagles, herons, otters, and raccoons.
Wild animals aren't the only ones who benefit from access to these sedges: Carex species have been a valuable resource for Indigenous societies in the Pacific Northwest, who use the leaves, stems, and rhizomes, or root-producing underground stems, for a number of purposes. The tough leaves have been woven into rope, baskets, and mats; provided insulation for footwear; and been used as torches, packing material for fragile items, lining for cooking pits, and even shaving tools. The rhizomes can be split in a delicate process to extract fibers, which are then used to weave mats and clothing, while the stems have been used by certain Indigenous groups as food or animal feed. These multi-purpose plants are either harvested from shorelines or cultivated in sedge beds expressly set aside for harvest. Today, people of the Nitinaht and Nootka nations continue the practice of weaving baskets and mats with Carex leaves.
In the Green Futures Lab context, this is the first year deploying Carex species in the wetland biofilters, so we’re still gathering information on their performance. Though the containment of the biofilters means these sedges can't contribute to structural changes in the river, they still have the potential to provide important shelter and food for birds, juvenile fish, and small aquatic invertebrates. Follow the GFL socials [Facebook, Instagram] to learn more about these results once the team begins analyzing the field season data!
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