Adaptation of restoration target with climate change: the case of a coastal peatland

As a rise in sea level is expected with climate change, peat-extracted peatlands located in coastal zones are more vulnerable to saltwater intrusion. Seawater contamination may prevent revegetation of typical bog species (e.g., Sphagnum, ericaceous shrubs) generally intolerant to saline conditions. Spontaneous revegetation was studied in a 27-year post-extracted bog that has been contaminated with seawater in New Brunswick (Eastern Canada). This study aimed (i) to evaluate spontaneous plant regeneration on saline but still acidic, organic soil; and (ii) to relate the recolonized vegetation patterns to the main environmental conditions. Of the seven plant communities found in the sea-contaminated bog, none were typical of bogs, and Sphagnum mosses were poorly represented. Plants communities and chemical properties were rather representative of salt marsh ecosystems (i.e., Carex paleacea, Sporobolus michauxianus, Empetrum nigrum, Myrica gale; neutral pH and nutrient-rich, namely P, Mg, and NH4+). Areas with low levels of spontaneous revegetation were associated with harsh chemical conditions (i.e., acid pH, high electrical conductivity, and nutrient-poor). Considering the aggravating factors that will persist with climate change, restoration of coastal bogs contaminated with seawater should aim to re-establish salt marsh ecosystems, given that spontaneous revegetation patterns and chemical conditions clearly do not allow the establishment of bog plant communities.