Restoring peatlands to their (almost) natural state

In 5 seconds A new study shows that artificial ponds created to restore peatlands exploited by humans achieve a balance similar to that of natural ponds, but it takes time.
Julien Arsenault, Jean-François Lapierre et Émilie Jolin autour d’une mare naturelle de la tourbière Grande plée Bleue, à Lévis. Couvrant près de 1500 hectares (15 km carrés), cette tourbière est l’une des plus vastes et rares tourbières du sud du Québec encore à l’état naturel.

Ponds created to restore bogs degraded by peat extraction take over 17 years to develop ecosystems similar to natural ponds.

That is the finding of a study by master’s students Émilie Jolin and Mahmud Hassan and doctoral student Julien Arsenault, supervised by Julie Talbot of the Department of Geography at Université de Montréal and Line Rochefort at Université Laval. Their results were recently published in Ecological Applications.

Peatlands are age-old ecosystems that play a key role in mitigating climate change because of their capacity to store vast amounts of carbon as organic matter. In a process spanning tens of thousands of years, they accumulate this organic matter, which we call peat, to a depth of up to seven metres.

But intensive exploitation of peatlands for purposes such as horticultural peat has led to their degradation. In eastern Canada, efforts to restore these peatlands to their natural state have been underway for the past 25 years.

Part of this process involves artificially recreating the shallow pools that typically dot peatlands. These pools are especially important for local biodiversity as they provide habitat for a wide range of amphibian, bird and plant species.

Created pools significantly different from natural ones

Julie Talbot

The study examined 61 pools–29 natural and 32 created–located in seven peatlands in New Brunswick and eastern Quebec. The peatlands studied are all ombotrophic, meaning they receive all their water and nutrients from precipitation rather than from streams or springs. Another characteristic they share is the presence of sphagnum moss, which decomposes very slowly and causes natural acidification.

In summer 2020 and 2021, the researchers took water samples to compare the biochemical composition of the two types of pools. They also examined changes over time in the created pools, which ranged in age from 3 to 22 years.

The analysis covered a range of different compounds and elements, including essential nutrients (nitrogen and phosphorus), organic matter indicators (dissolved organic carbon), minerals (calcium, sodium, magnesium and potassium) and dissolved gases (methane, carbon dioxide and nitrous oxide).

The results revealed significant differences between the natural and created pools.

“With a pH above 5, the created ponds were less acidic than their natural counterparts, so their chemical properties were quite different,” reported Talbot. “They also contained 2.5 times more nutrients, particularly nitrogen and phosphorus, which could foster algal blooms and create potentially anoxic conditions harmful to some species.”

The analysis also showed that concentrations of dissolved organic matter, gases and minerals were consistently higher in the created pools.

“These differences can be explained in part by the initial absence of sphagnum moss, which is characteristic of peat bogs and shapes their chemistry by naturally acidifying the water and regulating nutrient concentrations,” said Talbot.

Ecosystem preservation must be the top priority

The researchers also made another important discovery: ponds created more than 17 years ago showed biochemical characteristics approaching those of natural ponds. This suggests that, given enough time, artificial ponds can evolve towards conditions similar to those of natural ponds.

In short, this study demonstrates that it is possible to restore damaged ecosystems, a hopeful message as we head toward the midway mark of the UN Decade on Ecosystem Restoration (2021 to 2030).

However, Talbot believes that preserving intact peatlands must remain the top priority.

“While restoration is possible and gives good results, it must not serve as a justification for peatland exploitation,” she said. “Restoration takes years, even decades, to repair what exploitation destroys in a short space of time.”

Student and teaching assistant Marie-Pier Ménard, from the UdeM Department of Geography, samples a pond in the Grande-Plée-Bleue peat bog in Lévis.
No fewer than 61 ponds were sampled in seven peat bogs, four located in Quebec and three in New Brunswick.
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