Climate Change, Coastal Squeeze, and Boundary Bay Salt Marshes
By Jamesa Ensing
Keywords: Salt Marsh, Boundary Bay, Sea Level Rise, Climate Change, Dike, Sediment
Summary
Salt marshes, like Boundary Bay, British Columbia, are important coastal habitats that provide significant ecosystem services such as blue carbon storage/carbon accumulation, socio-cultural value, storm protection and flood mitigation, and critical habitat (Leo, et al., 2019; Moritsch, et al., 2022; Gailis, et al., 2021). Though blue carbon ecosystems only make up about 0.2% of ocean surface, they store up to 50% of total coastal oceanic carbon with a rate of carbon sequestration often higher than terrestrial forest soils (Chastain, et al., 2022; Moritsch, et al., 2022). However, as anthropogenic climate change escalates, Boundary Bay and other coastal wetland ecosystems are put at risk of coastal squeeze: where the combined effects of sea level rise and coastal urbanization/development cause the shrinking of ecosystems such as salt marshes and beaches that hinders their ability to adapt to climate change (Chávez, et al., 2021; Torio & Chmura, 2013). In order for salt marshes to survive amidst sea level rise, they must migrate landwards, which is often prevented by man made dikes, or accrete sediment vertically, which is determined by sediment availability often modified by anthropogenic activity (Tice-Lewis, et al., 2022; Moritsch, et al., 2022). Can anthropogenic activity also increase the resilience and longevity of salt marshes? Restoration efforts in Boundary Bay and other coastal wetland areas have proved a worthwhile effort to increase the resiliency of these ecosystems (Gailis, et al., 2021). As coastal squeeze becomes imminent in more and more places, forcing out already threatened ecosystems, the necessity for mitigation and restoration activities also increases (Moritsch, et al., 2022).
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Ecological geneaology
Boundary Bay is the largest salt marsh in southwestern Canada, providing significant critical habitat, flood protection, and carbon accumulation potential (Gailis, et al., 2021). As such, in 1986-1987 the Government of British Columbia designated a portion of the salt marsh as a provincial Wildlife Management Area (Gailis, et al., 2021). Boundary Bay is found on Hul’qumi’num, Lkwungen, and SENĆOŦEN speaking peoples territory, comprising of a number of Straits Salish nations including the Semiahmoo First Nation, Stz’uminus First Nation, Katzie First Nation, and Tsawwassen First Nation (Native-Land.ca, n.d.). Additionally, scholars in the 1950s state Boundary Bay and its surrounding waters are known as a “place which drew fishermen from great distances,” as it hosted seasonal visitors from many Nations around Vancouver Island and coastal British Columbia/Washington (Mitchell, 1992, p. 18). The waters were used to fish salmon and harvest clams, mussels, oysters, cockles, wild berries, roots, waterfowl, and sea mammals by the Semiahmoo, Snokomish, Katzie, Tsawwassen, Stz’uminus, and First Nations from surrounding areas: Cowichan, Nanaimo, Musqueam, Saanich, Songhees, Samish, and Lummi (Michell, 1992). Geologically, the Fraser River delta is recent with nearby Boundary Bay theorized as a relatively new salt marsh, accumulating sediment for between 33-124 years before present (BP) (Gailis, et al., 2021). The deglaciation of the Fraser Lowland around 11,000 years BP led to the formation of the Fraser River delta as the Fraser River deposited sediments carried through a glacial trough (Atkins, et al., 2016). Since 5000 years BP to present the Fraser River discharges west into the Salish Sea (formerly the Strait of Georgia).
Boundary Bay underwent significant structural changes through colonization and settlement (Gailis, et al., 2021). In the 1880s, farmers constructed a dike at the northern part of the marsh to prevent flooding into their farmlands (Gailis, et al., 2021). This dike was reinforced by the City of Delta after the great flood of 1948 and is now the marsh’s landward boundary (Gailis, et al., 2021). Additional disturbances to the site include vigorous logging activity and deforestation in the 1960s-1970s contributing to washed up logs and potential contamination (Gailis, et al., 2021; Atkins, et al., 2016). Additionally, dredging of the Serpentine and Nikomekl Rivers — which empty and deposit sediment into the easternmost point of the bay — since the 1800s contributes to decreased sediment availability (Gailis, et al., 2021; Atkins, et al., 2016). Pre-1980s, the dominant discourse around salt marshes dictated that they were growing, continually accumulating sediment before eventually becoming land and only subject to episodic erosion (Hatvany, Cayer & Parent, 2015). However, post-1980s the dominant paradigm shifted to declare salt marshes were largely eroding mostly due to human disturbances (Hatvany, Cayer & Parent, 2015). Salt marsh ecosystems are now viewed as “dynamically evolving land-forms” that experience both varying sediment budgets and erosive action due to human disturbances and environmental conditions (Hatvany, Cayer & Parent, 2015). |
Present tense
Within salt marsh ecosystems, healthy and mature vegetation generally forms zoned communities according to species tolerance of abiotic conditions such as salinity and flooding frequency (Rabinowitz & Andrews, 2022). Many of these salt tolerant species are harvested for food by First Nations and others in Canada such as Glasswort/Sea Asparagus (Salicornia spp.), Seaside Plantain (Plantago maritima), Springbank Clover (Trifolium wormskioldii), Orache (Atriplex spp.), and Pacific Silverweed (Potentilla egedii) (Rabinowitz & Andrews, 2022). Unfortunately, many of these species are threatened by introduced species that invade salt marsh ecosystems, for example, on the West Coast of Canada: Sporobolus spp. Grasses, Narrow-leaved Cattail (Typha angustifolia), and Blue Cattail (Typha x glauca) (Rabinowitz & Andrews, 2022). In Boundary Bay, low marsh sites host predominantly native Glasswort/Sea Asparagus (Salicornia virginica) and Seaside Arrowgrass (Triglochin maritima) (Gailis, et al., 2021). The high blue carbon accumulation and storage of salt marshes is largely due to plant communities’ primary productivity and growing biomass in the ecosystem (Rabinowitz & Andrews, 2022). Glasswort/Sea Asparagus (Salicornia spp.) are the dominant carbon accumulators in low marsh areas and Orache (Atriplex spp.) dominate high marsh carbon accumulation (Gailis, et al., 2021).
Additionally, many fauna utilize the Boundary Bay salt marsh including numerous bird species consisting of but not limited to: Mallard (Anas platyrhynchos), American Wigeon (Mareca americana), Great Blue Heron (Ardea herodias), Black-bellied Plover (Pluvialis squatarola), Western Sandpiper (Calidris mauri), Red-tailed Hawk (Buteo jamaicensis), and Bald Eagle (Haliaeetus leucocephalus) (Province of BC, n.d.). Also, the endangered Barn Owl (Tyto alba) uses the marsh to forage (Province of BC, n.d.). Other mammals such as Harbour Seals (Phoca vitulina), Grey Whales (Eschrichtius robustus), and Killer Whales (Orcinus orca) are found in the bay nearby and Pacific Herring (Clupea pallasii), Striped Bass (Morone saxatilis), American eel (Anguilla rostrata) and others spawn in the eelgrass beds of the marsh (Province of BC, n.d.; Robinowitz & Andrews, 2022). Chemically, salt marsh soils are modified by organisms such as crustaceans and fish trapped in wet mud during low tide as well as through the slow decomposition of plant species as sediment increases (Rabinowitz & Andrews, 2022). The human constructed dike along the northside of the Boundary Bay salt marsh is presently undergoing further reinforcement by the City of Delta — an increase of 4.7 metres — to mitigate increased flooding and anticipated sea level rise due to climate change (Boundary Bay Dike, 2024). This dike actively prevents landward movement of the Boundary Bay salt marsh in the face of rising sea levels leaving the only other option for survival to accrete sediment for vertical growth of the marsh. However, sediment accumulation at Boundary Bay is generally low, as Point Roberts peninsula blocks most sediment from the Fraser River from reaching the salt marsh (Gailis, et al., 2021). Any sediment accumulation comes from loose sediment from the cliffs at Point Roberts, and minor deposits from the Serpentine and Nicomekl rivers (Gailis, et al., 2021). The meager inflow of sediment to the Boundary Bay salt marsh suggests that the salt marsh — having a reinforced dike at the north end and low sediment inflow — may eventually be squeezed out, eroded, and submerged by sea level rise (Moritsch, et al., 2022). In 2023, restoration work by Ducks Unlimited Canada took place in Boundary Bay to improve the conditions of high marsh areas by removing human produced driftwood washed ashore, (driftwood without large root wads or branches), mitigating potential contaminants and decreasing risk of hypoxia and sediment compaction of high marsh areas (Boundary Bay Tidal Marsh, n.d.). This restoration work does not negate the consequences of the dike, prohibiting additional sediment inflow from occasional flooding as well as salt marsh migration inward as sea levels rise. Complexities arise in management as Boundary Bay Regional Park is part of the City of Delta’s jurisdiction, the Wildlife Management Area is under the Province of British Columbia’s jurisdiction, and beyond the toe of the dike Boundary Bay is Crown land (Environmentally Sensitive Areas, n.d.). The inherent and constitutionally protected rights and jurisdiction of Indigenous peoples must also be considered. As the United Nations Declaration on the Rights of Indigenous Peoples Act, which Canada signed on June 21, 2021, states: the government of Canada is constitutionally required to consult Indigenous peoples on matters that may affect potential or established treaty rights; it must respect free, prior and informed consent protocols; and it must work with Indigenous Nations towards reconciliation (Government of Canada, 2021). The Canadian Constitution Act of 1982 in Section 35 “recognizes the inherent right of self-government as an existing Aboriginal right,” and therefore Indigenous peoples must be consulted on the modification of salt marsh ecosystems on their territories (Government of Canada, 2008). Additionally, UNDRIP supports this in Article 26:1 stating: “Indigenous peoples have the right to the lands, territories and resources which they have traditionally owned, occupied or otherwise used or acquired” (Government of Canada, 2021). Article 26:2 affirms “Indigenous peoples have the right to own, use, develop and control the lands, territories and resources...” followed by Article 26:3, “states shall give legal recognition and protection to these lands, territories and resources” (Government of Canada, 2021). |
Future trajectory
When looking ahead, there are a few options to be considered including to not take any action. Research of the complex relationships between sea level rise, sediment, and carbon accumulation in salt marshes reveals that sediment levels must increase significantly for existing marsh communities to survive sea level rise and maintain carbon accumulation through preserving transitional marsh area, preventing its eventual conversion to mudflat with sea level rise (Moritsch, et al., 2022). However, if sediment levels do not increase, significant habitat loss — particularly of high marsh area — and subsequent loss of carbon storage will occur (Mortisch, et al., 2022). The carbon storage capacities of salt marshes combined with other ecosystem services like flood mitigation, storm protection, fish production, recreational and cultural activities, and aesthetics combine to yield significant economic value in addition to the intrinsic value of these ecosystems that is worth protecting (Moritsch, et al., 2022; Rabinowitz & Andrews, 2022). Multiple studies suggest that quantifying salt marsh carbon storage potential can help governments prioritize these ecosystems in restoration and management efforts; they provide nature-based solutions to climate change through mitigating greenhouse gas emissions (Gailis, et al., 2021). Additionally, research shows that coastal marshes could mitigate flood depths by 15%, potentially saving millions of dollars, further increasing the economic value of these ecosystems (Rabinowitz & Andrews, 2022). To do nothing alongside rising sea levels would result in significant ecological and economic loss.
Another option is manual sediment input into at-risk salt marshes: engineering a sediment budget to combat the effects of sea level rise and sediment exportation that requires understanding of the complex geomorphology of coastal ecosystems (Ganju, 2019). Research shows that regardless of sea level rise, sediment loss combined with wave erosion can be detrimental to salt marshes over shorter timescales than sea level rise, highlighting the invaluable role of sediment budgets to marsh stability and vulnerability (Ganju, 2019). Sediment augmentation, or bringing in sediment from dredged tidal channels, inlets, or offshore areas to “increase vertical position relative to the tidal frame,” has been called a “vertical-only perspective” but nonetheless in cases where development constrains salt marshes from expanding landwards, manual sediment accretion is a justifiable attempt at maintaining their ecological and economic services (Ganju, 2019, p. 921). There is no record yet of sediment augmentation restoration efforts in the Boundary Bay salt marsh. A third option is implementing a living shoreline that is laterally focused and designed to mitigate the effects of waves and other erosive actions in an effort to make the salt marsh more resilient (Ganju, 2019). In 2018, the government of Canada committed to contributing funding to a nine year “living dike” project in collaboration with the City of Delta, the City of Surrey, and the Semiahmoo First Nation that works to combine “management and protection of coastal ecosystems with traditional, engineered flood protection,” is meant to mitigate habitat loss through coastal squeeze (Gailis, et al., 2021, p. 276). This ecologically designed option, while effective in mitigating erosive action on coastlines, risks decreasing necessary vertical sediment accretion through altering existing sediment pathways and replacing them with human sediment input (Ganju, 2019). This would potentially require human sediment bolstering of the salt marsh indefinitely. There are strong “physical processes that control geomorphic evolution of the coast” that remain somewhat ambiguous but crucial factors to coastal and salt marsh restoration activities including those at Boundary Bay (Ganju, 2019, p. 922). Despite erosion or slow sediment accretion, the Boundary Bay salt marsh is providing critical habitat to wildlife and delaying the impacts of sea level rise on surrounding ecosystems and infrastructure (Rabinowitz & Andrews, 2022). As the government and stakeholders design and implement restoration efforts at the Boundary Bay salt marsh, other effects of climate change beyond the scope of this study must also be considered, such as increased surface temperature and frequency of heat waves impacting vegetation in salt marshes. |
References
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Boundary Bay Dike Improvements | Let’s Talk Delta. (2024, March 6). Retrieved March 13, 2024, from https://letstalk.delta.ca/boundarybaydike
Boundary Bay Tidal Marsh Restoration Project. (n.d.). Ducks Unlimited Canada. Retrieved March 13, 2024, from https://www.ducks.ca/places/british-columbia/boundary-bay-tidal-marsh-restoration/
Chastain, S. G., Kohfeld, K. E., Pellatt, M. G., Olid, C., & Gailis, M. (2022). Quantification of blue carbon in salt marshes of the Pacific coast of Canada. Biogeosciences, 19(24), 5751–5777. https://doi.org/10.5194/bg-19-5751-2022
Chávez, V., Lithgow, D., Losada, M., & Silva-Casarin, R. (2021). Coastal green infrastructure to mitigate coastal squeeze. Journal of Infrastructure Preservation and Resilience, 2(1), 7. https://doi.org/10.1186/s43065-021-00026-1
Cole, J. (2023, November 16). This tidal marsh was dying. A new restoration project is reversing the trend. Rewilding Magazine. https://www.rewildingmag.com/boundary-bay-tidal-marsh-restoration/
Environmentally Sensitive Areas | City of Delta. (n.d.). Retrieved March 14, 2024, from https://www.delta.ca/community-culture/environment-conservation/environmentally-sens itive-areas
Gailis, M., Kohfeld, K. E., Pellatt, M. G., & Carlson, D. (2021). Quantifying blue carbon for the largest salt marsh in southern British Columbia: Implications for regional coastal management. Coastal Engineering Journal, 63(3), 275–309. https://doi.org/10.1080/21664250.2021.1894815
Ganju, N. K. (2019). Marshes Are the New Beaches: Integrating Sediment Transport into Restoration Planning. Estuaries and Coasts, 42(4), 917–926. https://doi.org/10.1007/s12237-019-00531-3
Government of Canada. (2008, November 3). The Government of Canada’s Approach to Implementation of the Inherent Right and the Negotiation of Aboriginal Self-Government [Reference material]. https://www.rcaanc-cirnac.gc.ca/eng/1100100031843/1539869205136
Government of Canada, Department of Justice. (2021, April 12). Backgrounder: United Nations Declaration on the Rights of Indigenous Peoples Act. https://www.justice.gc.ca/eng/declaration/about-apropos.html
Hatvany, M., Cayer, D., & Parent, A. (2015). Interpreting Salt Marsh Dynamics: Challenging Scientific Paradigms. Annals of the Association of American Geographers, 105(5), 1041–1060. https://doi.org/10.1080/00045608.2015.1059172
Leo, K. L., Gillies, C. L., Fitzsimons, J. A., Hale, L. Z., & Beck, M. W. (2019). Coastal habitat squeeze: A review of adaptation solutions for saltmarsh, mangrove and beach habitats. Ocean & Coastal Management, 175, 180–190. https://doi.org/10.1016/j.ocecoaman.2019.03.019
Mitchell, L. S. (1992). The Archaeology of the Dead at Boundary Bay, British Columbia: A History and Critical Analysis. Simon Fraser University.
Moritsch, M. M., Byrd, K. B., Davis, M., Good, A., Drexler, J. Z., Morris, J. T., Woo, I., Windham-Myers, L., Grossman, E., Nakai, G., Poppe, K. L., & Rybczyk, J. M. (2022). Can Coastal Habitats Rise to the Challenge? Resilience of Estuarine Habitats, Carbon Accumulation, and Economic Value to Sea-Level Rise in a Puget Sound Estuary. Estuaries and Coasts, 45(8), 2293–2309. https://doi.org/10.1007/s12237-022-01087-5
Native-Land.Ca. (n.d.). Retrieved March 13, 2024, from https://native-land.ca/
Province of British Columbia. (n.d.). Boundary Bay Wildlife Management Area. Retrieved March 12, 2024, from https://www2.gov.bc.ca/gov/content/environment/plants-animals-ecosystems/wildlife/wil dlife-habitats/conservation-lands/wma/wmas-list/boundary-bay
Rabinowitz, T., & Andrews, J. (2022). Valuing the Salt Marsh Ecosystem: Developing Ecosystem Accounts. Statistics Canada, 16.
Tice‐Lewis, M., Zhang, Y. S., Redding, S. G., Lindquist, N. L., Rodriguez, A. B., Fieseler, C. M., Walker, Q. A., & Fodrie, F. J. (2022). Coastal squeeze on temperate reefs: Long‐term shifts in salinity, water quality, and oyster‐associated communities. Ecological Applications, 32(5), e2609. https://doi.org/10.1002/eap.2609
Torio, D. D., & Chmura, G. L. (2013). Assessing Coastal Squeeze of Tidal Wetlands. Journal of Coastal Research, 290, 1049–1061. https://doi.org/10.2112/JCOASTRES-D-12-00162.1
Boundary Bay Dike Improvements | Let’s Talk Delta. (2024, March 6). Retrieved March 13, 2024, from https://letstalk.delta.ca/boundarybaydike
Boundary Bay Tidal Marsh Restoration Project. (n.d.). Ducks Unlimited Canada. Retrieved March 13, 2024, from https://www.ducks.ca/places/british-columbia/boundary-bay-tidal-marsh-restoration/
Chastain, S. G., Kohfeld, K. E., Pellatt, M. G., Olid, C., & Gailis, M. (2022). Quantification of blue carbon in salt marshes of the Pacific coast of Canada. Biogeosciences, 19(24), 5751–5777. https://doi.org/10.5194/bg-19-5751-2022
Chávez, V., Lithgow, D., Losada, M., & Silva-Casarin, R. (2021). Coastal green infrastructure to mitigate coastal squeeze. Journal of Infrastructure Preservation and Resilience, 2(1), 7. https://doi.org/10.1186/s43065-021-00026-1
Cole, J. (2023, November 16). This tidal marsh was dying. A new restoration project is reversing the trend. Rewilding Magazine. https://www.rewildingmag.com/boundary-bay-tidal-marsh-restoration/
Environmentally Sensitive Areas | City of Delta. (n.d.). Retrieved March 14, 2024, from https://www.delta.ca/community-culture/environment-conservation/environmentally-sens itive-areas
Gailis, M., Kohfeld, K. E., Pellatt, M. G., & Carlson, D. (2021). Quantifying blue carbon for the largest salt marsh in southern British Columbia: Implications for regional coastal management. Coastal Engineering Journal, 63(3), 275–309. https://doi.org/10.1080/21664250.2021.1894815
Ganju, N. K. (2019). Marshes Are the New Beaches: Integrating Sediment Transport into Restoration Planning. Estuaries and Coasts, 42(4), 917–926. https://doi.org/10.1007/s12237-019-00531-3
Government of Canada. (2008, November 3). The Government of Canada’s Approach to Implementation of the Inherent Right and the Negotiation of Aboriginal Self-Government [Reference material]. https://www.rcaanc-cirnac.gc.ca/eng/1100100031843/1539869205136
Government of Canada, Department of Justice. (2021, April 12). Backgrounder: United Nations Declaration on the Rights of Indigenous Peoples Act. https://www.justice.gc.ca/eng/declaration/about-apropos.html
Hatvany, M., Cayer, D., & Parent, A. (2015). Interpreting Salt Marsh Dynamics: Challenging Scientific Paradigms. Annals of the Association of American Geographers, 105(5), 1041–1060. https://doi.org/10.1080/00045608.2015.1059172
Leo, K. L., Gillies, C. L., Fitzsimons, J. A., Hale, L. Z., & Beck, M. W. (2019). Coastal habitat squeeze: A review of adaptation solutions for saltmarsh, mangrove and beach habitats. Ocean & Coastal Management, 175, 180–190. https://doi.org/10.1016/j.ocecoaman.2019.03.019
Mitchell, L. S. (1992). The Archaeology of the Dead at Boundary Bay, British Columbia: A History and Critical Analysis. Simon Fraser University.
Moritsch, M. M., Byrd, K. B., Davis, M., Good, A., Drexler, J. Z., Morris, J. T., Woo, I., Windham-Myers, L., Grossman, E., Nakai, G., Poppe, K. L., & Rybczyk, J. M. (2022). Can Coastal Habitats Rise to the Challenge? Resilience of Estuarine Habitats, Carbon Accumulation, and Economic Value to Sea-Level Rise in a Puget Sound Estuary. Estuaries and Coasts, 45(8), 2293–2309. https://doi.org/10.1007/s12237-022-01087-5
Native-Land.Ca. (n.d.). Retrieved March 13, 2024, from https://native-land.ca/
Province of British Columbia. (n.d.). Boundary Bay Wildlife Management Area. Retrieved March 12, 2024, from https://www2.gov.bc.ca/gov/content/environment/plants-animals-ecosystems/wildlife/wil dlife-habitats/conservation-lands/wma/wmas-list/boundary-bay
Rabinowitz, T., & Andrews, J. (2022). Valuing the Salt Marsh Ecosystem: Developing Ecosystem Accounts. Statistics Canada, 16.
Tice‐Lewis, M., Zhang, Y. S., Redding, S. G., Lindquist, N. L., Rodriguez, A. B., Fieseler, C. M., Walker, Q. A., & Fodrie, F. J. (2022). Coastal squeeze on temperate reefs: Long‐term shifts in salinity, water quality, and oyster‐associated communities. Ecological Applications, 32(5), e2609. https://doi.org/10.1002/eap.2609
Torio, D. D., & Chmura, G. L. (2013). Assessing Coastal Squeeze of Tidal Wetlands. Journal of Coastal Research, 290, 1049–1061. https://doi.org/10.2112/JCOASTRES-D-12-00162.1