On some coastlines tidal wetlands are threatened by high rates of relative sea level rise causing increased tidal submergence of vegetation at the seaward edge and eventual demise of the vegetation and loss of marsh there. Historically, tidal wetlands have been able to accrete vertically and laterally to expand at the inland edge. However, in many locations development of adjacent inland areas presents barriers to migration of wetlands, putting them in a “coastal squeeze”. The remote lands around Canada’s James Bay have no little development, but pose a different kind of coastal squeeze, thus loss of tidal marsh and its ecosystem services, including some unique to Cree residents. On James Bay tidal marshes are important staging areas for migratory waterfowl. For the James Bay Cree their fall goose hunt provides an important source of food, but also has significant cultural importance.
Results/Conclusions
Isostatic rebound of 2 m over the last 100 years has caused the sea to retreat and the tidal marsh to expand seaward. Cree complain that the “land is growing”, forcing them to relocate their hunting camps to keep them at the coast and hydrologically manage marshes to attract geese to their traditional hunting grounds. At the same time, isostatic rebound causes the inland edge of the marshes to rise out of the tidal frame. Creeping alkaligrass (Pucinellia phryganodes) -dominated marshes transition to tidal fens and eventually to poor fens and bogs. One would think that increasing rates of eustatic sea level rise would have a positive impact, by slowing the rate of decline of relative sea level. However, at the inland edge of the marsh the transition from minerotrophic, high productivity marshes to ombrotrophic peatlands is largely facilitated by mosses that establish in the canopy of sedges. Thus, loss of the tidal marsh at the inland edge, driven by a combination of isostatic rebound and autogenic processes, will continue at the same rate while the increased rate of eustatic sea level rise reduces the rate of seaward wetland formation. Even here, the increased rates of eustatic sea level rise driven by anthropogenic climate warming will cause a net loss of tidal wetlands and important ecosystem services.