Erin Zimmerman

Plant biologist turned science writer and illustrator with a BSc in plant biology and physics from the University of Guelph and an MSc and PhD in fungal genetics and molecular systematics, respectively, from the Université de Montréal.

Extracted peatlands contaminated by seawater may be better restored as salt marshes

June 22, 2020 | 3 minute read

With climate change leading to both a rise in sea level and increasingly severe and frequent weather events, coastal ecosystems are ever more threatened. Resource extraction such as that carried out by the peat industry, is compounding this threat.

Peat extraction removes both vegetation and a layer of peat, lowering the topography. When sea levels are high, extracted peatlands along coasts are left exposed to potential saltwater contamination, which raises sodium in the soil to two to three times natural levels.

The characteristic flora of peatlands, and Sphagnum mosses in particular, have low tolerance for salt, making active restoration of these extracted sites with their original species impossible.

However, restoration of extracted peatlands is essential to preventing soil erosion. Erosion of stripped peatlands can lead to sedimentation that disrupts marine ecosystems.

To inform restoration practices, a new study published in Botany looked at spontaneous revegetation in a salt-contaminated peatland in New Brunswick, Canada. Over a third of Canadian peat production occurs in New Brunswick and peat extraction is important to the province’s economy; in 2013 the provincial industry was valued at $150 million.

Dr. Mélina Guêné-Nanchen, a post-doctoral fellow at Laval University, and colleagues studied Pigeon Hill, a peat-extracted bog in the Acadian Peninsula. The bog, which was extracted 27 years prior to the study, has undergone spontaneous revegetation but is still susceptible to saltwater intrusion.

The researchers conducted plant and soil surveys to assess the returning plant communities as well as the electrical conductivity (a proxy for salinity) and nutrient content of the site.

Spontaneous revegetation of the peat-extracted bog did not reproduce plants associated with peat bogs but an assemblage of seven plant communities resembling a salt marsh. Soil conditions varied across the site, but in some areas they were acidic, saline, and nutrient-poor—all conditions present in salt marshes.

These results suggest that for sites with ongoing seawater intrusion, the establishment of a salt marsh ecosystem is a more realistic objective than reestablishing the original peat bog.

Extracted peatland on coast of New Brunswick

Post-extracted peatland, spring of 2019 | Mélina Guêné-Nanchen

 

The researchers propose the best course of action for restoring extracted coastal peatlands is to let them spontaneously move toward salt marsh vegetation or to actively plant with salt marsh species.

“Salt marshes, as long as they are vegetated, could provide [at least the same] level of protection from erosion, wave impact, and storm damage as peatlands. Salt marshes also filter pollution by decreasing water velocity and increasing the surface where sediments and pollutants can deposit,” says Guêné-Nanchen, noting that spontaneous revegetation can take decades to provide these services.

Could a salt-contaminated site not subject to ongoing seawater intrusion be rehabilitated to a peat bog?

Guêné-Nanchen isn’t optimistic about this scenario. “If salt contamination originated from an isolated event, salt concentration may remain low enough to allow the reintroduction of Sphagnum mosses. But we believe that with climate change, if sea intrusion happened once, it will probably happen again, and therefore, salt will continue to accumulate.”

Read the paper: Adaptation of restoration target with climate change: the case of a coastal peatland in Botany.

Erin Zimmerman

Plant biologist turned science writer and illustrator with a BSc in plant biology and physics from the University of Guelph and an MSc and PhD in fungal genetics and molecular systematics, respectively, from the Université de Montréal.