Wetlands: our researchers in action!

Write by Audrey-Maude Vézina

February 13, 2020

( update : September 15, 2020 )

Wetlands occupy about 10 percent of Quebec’s territory and nearly twice as many in Canada. Discover the research projects of four INRS professors related to these particular habitats: mapping, ecology, peatland exploitation and hydrology.

Les zones humides : nos chercheurs en action !


Where are Canadian wetlands located?

Marshes, swamps, bogs and surface waters. The spatial distribution of wetlands is crucial for the sustainable management and preservation of these fragile ecosystems. Professor Saeid Homayouni collaborated with a team of researchers across North America, including some from Memorial University of Newfoundland, to generate the first nation-wide wetland map with such a high level of detail.

Saeid Homayouni, professeur en télédétection et géomatique environnementale à l’Institut national de la recherche scientifique
Professor Saeid Homayouni

They managed to achieve a resolution of 10 metres for all of Canada, rather than the usual 30 metres. The map makes it possible to observe wetlands as small as 10 m2. Eventually, Professor Homayouni hopes to achieve accuracy better than 5 metres. “It would be interesting to have a high level of detail for targeted areas. It would make it possible to study several parameters such as land cover by vegetation, water or rocks,” says the remote sensing and environmental geomatics researcher.

The map of Canada even indicates the type of wetlands. To classify them, the research team took advantage of the available baseline data. “We used the information gathered by the field researchers. They identify which areas correspond to which wetland types. This information served as a learning base for the algorithm. We could then ask them to find similar types in the satellite images,” explains Saeid Homayouni.

Marais, marécages, tourbières et eaux de surface. La répartition spatiale des zones humides est cruciale pour la gestion durable et la préservation de ces écosystèmes fragiles. Le professeur Saeid Homayouni a collaboré avec une équipe de chercheurs en Amérique du Nord, dont certains de l’Université Memorial de Terre-Neuve, afin de générer la première carte des milieux humides à l’échelle du pays avec un niveau de détails aussi élevé.     Ils ont atteint une résolution de 10 mètres pour l’ensemble du Canada, plutôt que les 30 mètres habituels. La carte permet donc d’observer des zones humides aussi petites que 10 m2. Le professeur Homayouni veut augmenter la résolution pour étudier des surfaces de moins de 5 m2. « Avec ce haut niveau de détails pour des zones ciblées, ça nous permettrait d’analyser plusieurs paramètres comme la couverture du sol par la végétation, l’eau ou les roches », lance le chercheur en télédétection et géomatique environnementale, qui a rejoint l’INRS en avril 2019.     La cartographie du Canada indique même le type de zones humides. Pour les classifier, l’équipe de chercheurs a tiré profit des données de référence disponibles. « Nous avons utilisé les informations amassées par les chercheurs sur le terrain. Ils identifient quels secteurs correspondent à quels types de milieux humides. Ces informations ont servi de base d’apprentissage pour l’algorithme grâce auquel on a pu ensuite trouver des types similaires dans les images fournies par les satellites », explique Saeid Homayouni.
The first nationwide map of Canadian wetlands with 10 m resolution

Their mapping approach uses two types of satellite data. The “optical” data is effective in identifying wetland classes, but clouds and shading affect the quality of the images. The “radar” data are not sensitive to brightness or clouds. On the other hand, spurious signals (noise) can be superimposed on the signal of interest, making analysis more complex. Both sources have interesting characteristics and the combination compensates for the disadvantages.

The large amount of data requires a lot of computing power. To speed up the process, the team is exploiting cloud computing, which consists of a series of super-powered computers working in parallel. “You can go from weeks on one computer to just a few hours,” says Homayouni.

The researchers are now working with partners across the country to obtain more accurate baseline data. This will help identify important sites for high-resolution mapping. The map is based on data from 2016 to 2018, but could be updated annually. “Wetlands are showcases of climate change, so we need to be able to study their dynamics over the years,” says Professor Homayouni. The map will soon be available to the public through Natural Resources Canada and Ducks Unlimited Canada.

The ecological balance of aquatic ecosystems

Valérie Langlois, professeure en écotoxicogénomique à l’Institut national de la recherche scientifique
Professor Valérie Langlois

Buzzing mosquitoes, croaking frogs, singing birds—the wetlands are alive with a multitude of sounds, and home to great diversity of species. The source of this rich variety is the abundant yet concentrated food chain. “A great variety of prey is available, at all levels, within a small area. In an environment rich in nutrients and organic matter, phytoplankton and small algae proliferate. The large insect populations that lay their eggs in wetlands also provide a food source for amphibians, which are eaten by birds, and so on and so forth,” explains INRS professor and researcher Valérie Langlois.

Professor Langlois, whose specialty is ecotoxicogenomics, is particularly interested in amphibians like frogs, for which wetlands are a critical breeding ground. “It’s their love nest,” she notes. “They lay their eggs in marshes, where the water is stagnant. Since frog eggs don’t float, they have to attach them to something—a branch, a shrub, or submerged aquatic plants.”

Beyond providing habitat for a host of species, wetlands also serve to filter both surface water and groundwater. They absorb toxins, such as pesticides and road salt, that can impact the ecosystem. The potential negative impacts of such harmful compounds are exactly what Professor Langlois’s research seeks to understand.

Recently, she began studying an additional contaminant, Bti, a biopesticide used in wetlands near cities and in parks to hinder the reproduction of biting insects like mosquitos and black flies. While Professor Langlois’s focus is specifically on amphibians, there are potential repercussions for all wetland species. “If Bti kills certain insect larvae, that removes a level of the food chain and impoverishes the environment. On the other hand, if frogs are affected, they will no longer be able to control the population of certain insects. It’s an ecological balancing act,” she notes.

By ascertaining the harmful effects of chemicals in aquatic environments, Professor Langlois’s research is helping preserve Québec’s wetlands and the species that depend on them.

The challenges of Québec’s peatlands

Tractors equipped with vacuums are used to harvest peat—large deposits of organic material that gather in areas known as peatlands or bogs and that are used in horticulture. The generally spongy surface of these wetlands is first dried out with drainage canals, which carry water toward nearby waterways. But this water often carries sediment, which can drain off, creating problems in the ecosystem that receives it.

INRS professor André St-Hilaire works with Sophie Duchesne and Claude Fortin and private business to provide tools to assess and potentially mitigate the effects of drainage water on receiving waterways. One goal is to optimize the size of retention basins, which are essentially large pools on the edges of a drainage network. Basins give sediment a place to settle before they can reach waterways. But when basin dimensions are too small, a large proportion of sediment will overflow,” explains Professor St-Hilaire, an expert in environmental and statistical hydrology.

In addition to peat harvesting, André St-Hilaire has worked with Hydro-Québec on two aspects of peatlands. His work, along with that of Professor Alain Rousseau, has helped determine the amount of water retained by peat bogs surrounding dams, improving water flow forecasts. “The models Hydro-Québec was using didn’t effectively take into account the effect of peatlands,” says Professor St-Hilaire. “We knew that peatlands retained water, but we didn’t know to what extent.”

The other aspect of the collaboration concerns carbon retention in peatlands. Normally, peatlands store carbon as organic matter and gas. But the construction of dams can flood peat bogs, which will then re-emit a portion of this stored carbon. “It goes from being a carbon sink to a carbon source. Hydro-Québec wanted to determine how serious the emission problem was,” notes Professor St-Hilaire.

In collaboration with Professor Michelle Garneau (UQAR), André St-Hilaire used a water balance equation as a model to perform a “carbon balance.” Carbon is emitted as gases, such as CO2 released through photosynthesis or the methane emitted by some ponds. Carbon can also be found in wetland water. André St-Hilaire conducted a hydrological assessment by measuring the water entering the peat bog, the amount stored, and the water leaving. By measuring the amount of carbon indirectly dissolved in water and the suspended carbon particles, Professor Garneau’s team will be able to establish an overall portrait of carbon emissions from the peatlands bordering the Rivière Romaine watershed.

The key role of watershed

Alain Rousseau, professeur en modélisation hydrologique à l’Institut national de la recherche scientifique
Le Professor Alain N. Rousseau

Water flows downstream through varied environments toward the outfall, where it re-enters the watershed. Some routes may see the water’s flow temporarily stop in a wetland, before partially replenishing the underlying aquifer and bodies of water downstream. This “layover” in marshes, peatlands, and swamps attenuates low and high flows, reducing the risk of insufficient flow or, conversely, flooding.

Professor Alain N. Rousseau’s team studies the hydrological services provided by wetlands at the watershed level to assess how they modulate river flow rates.

His research with Monique Poulin of Université Laval is especially critical in light of Bill 132, An Act respecting the conservation of wetlands and bodies of water, which came into force in March 2018. This law calls for the conservation, restoration, and creation of new wetlands environments to offset the inevitable losses of wetlands and bodies of water. “The law stipulates that when wetlands are lost—to urban development for example—a new wetland of the same size must be recreated elsewhere. As hydrologists, we find this reductive. Creating wetlands the same size somewhere else will not provide the same hydrological service. The positioning of wetlands within the watershed influences the modulation of flows. Their loss disrupts the dynamics,” explains Professor Rousseau, an expert in hydrological modelling and integrated watershed management.

The destruction of a single wetland will not have much effect on the scale of the watershed. But the cumulative effect of losing multiple environments will be tangible, which is why Professor Rousseau prefers to think in terms of a network of wetlands. In collaboration with the City of Québec, he is working to identify wetlands networks, and to help implement preservation and restoration programs for isolated and riparian environments at the watershed level.

Professor Rousseau is also studying the effect of floods on agriculture in the Lake Champlain and Richelieu River basins and developing performance indicators. Funded by the International Joint Commission, this research grew out of the 2011 floods in Saint-Jean-sur-Richelieu. In Professor Rousseau’s words, “We’re also examining the impact of restoring certain wetlands in flooded areas. Where soil drainage is poor, a wetland environment may arise. When wetlands are drained for agricultural purposes, they can be revived through measures like removing drains. Water will accumulate, and the overflow will find a way to travel downstream. Then, you can foster the growth of aquatic plants that could support appropriate wildlife diversity.”

With more than 400 major watersheds in Québec, Professor Alain N. Rousseau’s work on wetlands is important in its own right and as part of a broader ecosystem analysis.