This is the second of three Public Lands Blog posts that focus on Oregon’s coast. Part 1 looked at Oregon’s (and the nation’s) “blue carbon” and a congressional effort to conserve and restore it. Part 2 examines coastal wetland loss, conservation, and restoration. Part 3 will describe a now very rare type of coastal wetland: the tidal swamp or tidal forested wetland.
Figure 1. Roosevelt elk grazing on emergent tidal marsh in the Nehalem River estuary. Source: Laura Brophy.
The good news is that Oregon has lost a far smaller percentage of its wetlands than many other states. Still, well over one-third of what was wet land is no longer wet. We shall examine interior wetlands—aka “teal carbon”—in a subsequent Public Lands Blog post. As for tidal wetlands on the Oregon coast, 54 percent of these wetlands have been lost; this includes the 92 percent of tidal swamps (wetlands dominated by shrubs or trees) that have been lost.
Before the European invasion, tidal wetlands of all kinds covered 0.06 percent of Oregon’s total area; today they cover just 0.03 percent. Historically, tidal wetlands in Oregon covered a grand total of 38,052 acres (~59 square miles), and today they cover just 17,525 acres (~27 square miles), with 20,527 acres (~32 square miles) having been lost. To put that in perspective, Devil’s Staircase Wilderness in the lower Umpqua Basin of Oregon’s Coast Range, established by Congress in 2019, totals 31,107 acres (~49 square miles).
Devil’s Staircase is one intact block of land. A challenge for Oregon’s tidal wetland conservation effort is that what needs to be preserved is not one or a few large blocks, but rather hundreds of relatively tiny parcels with vast numbers of individual landowners. A concerted and focused effort is needed to bring back the wetlands that are minute in area but colossal in importance.
Figure 2. A Pacific silverweed–Baltic rush emergent tidal marsh in the Coquille River estuary. Source: Laura Brophy.
Why Conserve Tidal Wetlands?
Tidal wetlands are full of carbon. Conserving tidal wetlands keeps carbon safely ensconced in the vegetation and soils, preventing its loss to the atmosphere (Figure 3). Restoring tidal wetlands could result in significant amounts of carbon dioxide being removed from the atmosphere—not to mention various water quality, water quantity, fish and wildlife habitat, flooding amelioration, and other benefits.
Figure 3. A simplified depiction of the coastal carbon cycle. (1) Very significant amounts of atmospheric carbon dioxide (CO2) are taken up by trees and other vegetation. Since they are near the coast, it rarely freezes, so growth occurs all year. (2) Carbon-bearing dead leaves, branches, and roots are buried in the soils, which are often covered by water, resulting in an anaerobic environment that results in extremely long-lived carbon stores. (3) Trees and other vegetation naturally respire, sending a small portion of the CO2 back to the atmosphere. The trees in the drawing are mangroves, but along the Oregon coast they would have been (and can again be) Sitka spruce trees. Source: NOAA National Ocean Service.
The Brophy Report
In December 2019, the Institute for Applied Ecology published a report by Laura Brophy comparing historical losses of different wetland types on the Oregon coast. Brophy (Figure 4) is director of the Estuary Technical Group at the Institute for Applied Ecology and a member of the graduate faculty of the Marine Resource Management Program of the College of Earth, Ocean, and Atmospheric Sciences at Oregon State University. No study before hers had measured the loss of forested tidal wetlands along the coast as a whole, so the potential ecological significance of the near eradication of this type of habitat had gone largely unrecognized.
Figure 4. Laura Brophy. The Pew Charitable Trusts characterized her as an “Oregon scientist and tidal swamp champion.” Indeed. Source: Doug Adams, NOAA National Geodetic Survey.
Brophy’s analysis was more complete than earlier studies due to many factors. In particular, it included any tidal (subject to tidal inundation) wetland from around the lowest marsh up to the highest tide of the year. A lot of the former and current forested swamp is in this zone that—on average—is inundated by the tides a few days out of each month. It also included all tidal wetlands from the ocean to the head of the tide, which included freshwater tidal wetlands. The freshwater is affected by tides but remains fresh as it is pushed around by, but does not intermix with, brackish water.
As a result of this more complete analysis, Brophy found that the previous study (by Dr. James Good of OSU in 2000) had underestimated the historical extent of tidal wetlands of all types by 34 percent. Thus, the loss of tidal wetlands had been underestimated (Figure 5).
Figure 5. A typical Oregon coast estuary as conceived in 1999. Today, Laura Brophy notes that there was originally a lot more tidal (scrub-shrub and forested) swamp than shown in the drawing. Source: Laura Brophy, based on original depiction by Dr. James Good, Oregon State University.
The Brophy Report is the source of most of the rest of the information in this Public Lands Blog post.
Oregon Tidal Wetlands 101
Each day Oregon’s coastal tidal wetlands are affected by lower low, low, high, and higher high tides. Some coasts only have one tide cycle each day, while other places have equal low and high tides each day. Who knew?!
Figure 6. Tidal marshes and tidal swamps. Both low and high marshes are “emergent” marshes. Scrub-shrub tidal swamps are dominated by woody vegetation such as willows. Forested tidal swamps on the Oregon coast are characterized by conifers, mainly Sitka spruce. Source: Laura Brophy.
Tidal wetlands are the vegetated lands between low and high tide. They also include open water areas and mudflats. Oregon’s vegetated tidal wetlands are either tidal marsh (aka tidal emergent wetland) or tidal swamp (Figures 5 and 6), defined as follows:
Tidal marsh: A tidal wetland with vegetation dominated by herbaceous plants such as grasses, sedges, rushes, and broad-leaved herbaceous plants. In Oregon and the Pacific Northwest, tidal emergent wetlands can be saline, brackish, or fresh.
Tidal swamp: A tidal wetland with vegetation dominated by woody plants (either shrubs or trees). In Oregon and the Pacific Northwest, tidal swamps can be brackish or fresh.
There are two kinds of tidal marsh: high marsh and low marsh. One is more inundated than the other, so the vegetation differs, but in either case this vegetation is not woody. According to Brophy:
Low marsh is often dominated by succulent halophytes (salt-tolerant species) like pickleweed (Salicornia pacifica, also called Sarcocornia perennis), jaumea (Jaumea carnosa), and seaside arrowgrass (Triglochin maritima). Very salt-tolerant grasses like saltgrass (Distichlis spicata) can also be dominant. High marsh is not dominated by succulents; dominants often include tufted hairgrass (Deschampsia cespitosa), Pacific silverweed (Potentilla anserina), and Baltic rush (Juncus balticus). High marsh can have a broad diversity of grasses, sedges, rushes, and forbs too, including many broad-leaved herbaceous flowering plants like Douglas aster, sea-watch angelica, yarrow, and gumweed.
Figure 7. The rare Henderson’s checkermallow (Sidalcea hendersonii, the lower pink-flowered plant) amid sea-watch angelica (Angelica lucida) on an emergent tidal marsh in the Siuslaw River estuary. Source: Laura Brophy.
There are two kinds of tidal swamps:
Tidal scrub-shrub wetland: A tidal wetland dominated by shrubs, with less than 10% cover of trees. . . . In Oregon and the Pacific Northwest, scrub-shrub tidal wetlands can be brackish or fresh.
Tidal forested wetland: A tidal wetland with more than 10% cover of trees. . . . In Oregon and the Pacific Northwest, tidal forested wetlands be brackish or fresh. Also called “tidal forest” or “tidal forest/woodland.”
(Part 3 of this series will focus on tidal swamps, especially tidal forested wetlands.)
The two major factors that determine the particular kind of tidal wetland we’re looking at are elevation and salinity. Elevation is the dominant factor in distinguishing a low marsh from a high marsh as both are quite saline. The elevation of a high marsh and a tidal swamp (scrub-shrub or forest) can be quite similar. It is the salinity that differs. The water in a Sitka spruce tidal swamp can range from brackish to completely fresh (Figure 8).
Figure 8. Elevation and level of salinity of the water clearly differentiate a low marsh from a high marsh. The elevation of a high marsh and a woody-dominated swamp are similar; their distribution depends on the brackishness of the water. Source: Laura Brophy.
The Oregon Coastal Estuaries Brophy Analyzed
Brophy studied the Oregon coast’s fifteen largest estuaries (Figure 9). Noting that they contain 96.5 percent of the coast’s historical tidal wetland area, she suggested that her results were representative of the coast in general.
Figure 9. The fifteen largest estuaries on the Oregon Coast, included in the Brophy report. Containing 96.5 percent of all coastal wetlands in Oregon (the Columbia River estuary is not coastal), they adequately characterize tidal wetlands along the coast in general. Source: Institute for Applied Ecology (Brophy 2019).
Of the twenty-two major Oregon estuaries listed in the Oregon Coastal Atlas, Brophy didn’t include eight: the Columbia River, Depoe Bay (quite small and the most human-developed of any), and six south-coast estuaries (Sixes, Elk, Rogue, Pistol, Chetco, and Winchuck). Limitations of the study design precluded inclusion of smaller estuaries such as these and others (including Ecola, Yachats, and Hunter). (Estuaries south of the Coquille generally come from a hardier geology less conducive to large estuaries, as big sand spits that protect such estuaries rarely form. Conversely, most of Oregon’s more than fourteen hundred islands, rocks, and reefs—another vital habitat type—are found offshore of this rockier geology.) On the other hand, Brophy included the Beaver Creek estuary, which is not considered to be a major estuary by the folks at Oregon Coastal Atlas.
Figure 10. A rough-skinned newt (Taricha granulosa) in the Siuslaw River estuary. Source: Laura Brophy.
While not including the Lower Columbia River Estuary (LCRE), Brophy cited the work of other researchers who have analyzed wetland loss there. For instance, one study found a 68.8 percent and 67.9 percent loss of tidal swamps and tidal marshes respectively. Another researcher found that 96 percent of wetlands in Astoria’s Youngs Bay in Oregon and 100 percent of wetlands in Ilwaco’s Baker Bay across the river have been lost (full citations in the Brophy report). Fortunately, there are still some areas of Sitka spruce swamp and scrub-shrub swamp in the Julia Butler Hansen National Wildlife Refuge on the Washington side, and of Sitka spruce swamp in the Lewis and Clark National Wildlife Refuge on the Oregon side.
Figure 11. Tidal marshes and swamps in the Siletz River estuary. One can explore them, but pay attention to the tide tables. Source: Laura Brophy.
The Losses: How Much and What Kinds
Since “settlement” (aka European invasion) in the early 1800s, what is now Oregon has lost 54 percent of its tidal wetlands (Table 1). Forested tidal swamps, generally characterized by the presence of Sitka spruce, have suffered the greatest loss at 92 percent.
Forested swamp has suffered the greatest relative loss. It used to make up the majority (54 percent) of Oregon’s coastal tidal wetlands, but today makes up only 10 percent (and the Sitka spruce trees are a lot smaller as well) (Chart 1). Table 2 summarizes the damage by estuary.
Chart 1. Oregon coastal wetland loss by type. The vast majority lost has been tidal swamp (blue and light green), in particular forested tidal swamp (blue). Source: Institute for Applied Ecology (Brophy 2019).
Conservation and Restoration
Be they low or high marsh or scrub-shrub or forested swamps, all tidal wetlands are worth conserving and restoring.
Figure 12. The Umpqua River estuary. Red has been diked; most was forested tidal swamp. The dark blue are new tidal wetlands since European settlement, but they are emergent marshes, not forested swamps. Source: Institute for Applied Ecology (Brophy 2019).
Conservation
Conserving tidal wetlands means having a secure form of ownership, with the landowner committed to conservation.
Senator Ron Wyden has proposed the River Democracy Act (S.192, 117th Congress), which would establish an Oregon Dunes Wild and Scenic River, including those portions of Berry Creek and Lily Lake, Sutton Creek, Siltcoos River, Takenitch Creek, Threemile Creek, Threemile Lake, and Tenmile Creek that are within and near the Oregon Dunes National Recreation Area. All of these streams (but not the lakes) are tidally influenced, and protecting them is a good idea.
The State of Oregon—through state land use planning goals and the state fill-removal wetlands law—somewhat protects tidal wetlands, but the protection is not adequate. Prevention of loss to development is the first step to adequate conservation. The Oregon Department of State Lands, by administrative rule, should permanently conserve its remaining tidal wetlands (and restore the rest) for the benefit of this and future generations.
• State parks and state wildlife management areas could be established or expanded along the coast for the purpose of tidal wetland conservation and restoration.
• National wildlife refuges (Oregon Islands, Bandon Marsh, Siletz Bay, Nestucca Bay, Three Arch Rocks, and Cape Meares) along the Oregon coast could be expanded and several new ones established.
• The Cascade Head Scenic-Research Area, administered as part of the Siuslaw National Forest, could be a model for estuary conservation and restoration elsewhere.
• The Forest Service could do more to conserve tidal wetlands at Sand Lake, Sutton Creek, and other areas the agency owns or could acquire, as it has at Drift Creek (Alsea Bay).
• Private land trusts could acquire more privately owned tidal wetlands from willing sellers, as did the Lower Nehalem Community Trust for its Sitka Wetlands property.
• Private landowners could donate (tax-deductible!) their tidal wetlands to a conservation entity.
Restoration
Conserving what is left of Oregon’s tidal wetlands is not sufficient. Much of what has been lost must be restored.
It is relatively far easier to restore a tidal marsh (low or high) than a tidal swamp (scrub-shrub or forested). We have more experience with tidal marsh restoration. Here we examine an example of successful marsh restoration in the Bandon Marsh National Wildlife Refuge. In the forthcoming Part 3, we will examine the challenges of tidal swamp restoration.
Fundamentally, tidal wetland restoration is about letting the tides back in. After removal of a tide gate and an associated berm, nature can do a lot of the restoration work. Sometimes, drain pipe in the former pasture must be removed and meandering filled-in channels re-dug to facilitate tidal influence. Also, unleash the beavers (Figure 13)! (See my Public Lands Blog post “Leave It to Beavers: Good for the Climate, Ecosystems, Watersheds, Ratepayers, and Taxpayers,” Part 1and Part 2.)
Figure 13. A beaver dam in the Siletz River estuary. Beavers, along with Sitka spruce (see Part 3), are system engineers in tidal wetlands. Personally, I favor millions of new dams across North America, but only if they are built by beavers. Source: Laura Brophy.
A Story of Successful Tidal Marsh Restoration
The now 889-acre Bandon Marsh National Wildlife Refuge was established in 1983. It now has two units. The Bandon Marsh unit is a salt marsh that has salt marsh, mudflat, and Sitka spruce–red alder riverbank communities. Most of the Ni-les’tun (“small fish dam in the river” in Coquille) unit was long a lowland diked cattle pasture. Four hundred acres of formerly cow-bombed tidal marsh has been restored. (At the time, this was the largest tidal marsh restoration project in Oregon. Since then, an even larger restoration project, 443 acres, has been completed on the south end of Tillamook Bay.) The rest of the unit was and is intertidal marsh, forested wetlands, grasslands, and upland forest. Figures 14, 15, 16, and 17 saved me at least four thousand words in telling the wonderful success story.
Figure 14. The Ni-les’tun unit before being acquired to be part of the Bandon Marsh National Wildlife Refuge in the Coquille estuary (2002 photo). The area was a refuge for livestock when this photo was taken, but before that it was a tidal wetland. Source: Laura Brophy.
Figure 15. Tide gates (2009 photo). They let freshwater out through the berm at low tide but don’t let salt water in at high tide. This tide gate no longer exists. Source: Laura Brophy.
Figure 16. Lyngbye’s sedge, Carex lyngbyei (2012 photo). This native thrives along the newly reconnected tidal channels, amid large logs placed for fish habitat. Source: Laura Brophy.
Figure 17. The Ni-les’tun unit in 2013. The tides now reach all the way across the 400+ acres of the unit. Source: John Bragg.
Figure 18. A California sea lion (Zalophus californianus) in an emergent wetland a few miles inland (as the sea lion swims) from the mouth of the Salmon River estuary in Lincoln County, Oregon. Source: Laura Brophy.
For More Information
• Laura S. Brophy, Estuary Technical Group, Institute for Applied Ecology, Corvallis, Oregon, December 2019, “Comparing historical losses of forested, scrub-shrub, and emergent tidal wetlands on the Oregon coast, USA: A paradigm shift for estuary restoration and conservation.” Prepared for the Pacific States Marine Fisheries Commission and the Pacific Marine and Estuarine Fish Habitat Partnership.
• Laura Brophy photographs: Oregon Tidal Marsh, Oregon Tidal Swamp, Intertidal Beaver Dams in Oregon
• US Fish and Wildlife Service, Ni-les’tun Marsh Restoration
• NOAA National Ocean Service, What is the carbon cycle?
• US Forest Service, Drift Creek Restoration
Figure 19. The transition from emergent tidal marsh to forested tidal swamp in the Yaquina River estuary. Part 3 of this series will go deep on tidal swamps, both scrub-shrub and forested. Source: Laura Brophy.