Introduction

1Climate warming has hydrological and physicochemical impacts that induce changes in Québec’s aquatic ecosystems. It threatens the flora and fauna inhabiting these environments, as well as the human uses associated with them. To slow the pace of these ecosystem changes, maintaining the integrity of lake and river riparian buffers is one of the most effective strategies. This is why, in 1987, in an effort to mitigate the impacts of climate change on lacustrine environments, the Government of Québec developed, implemented, and coordinated the Policy for the Protection of Lakeshores, Riverbanks, Littoral Zones and Floodplains (Ministère de l’Environnement, 1987). Under the Act Respecting Land Use Planning and Development, municipalities were required to adopt regulations based on this provincial policy to ensure the protection of riparian buffers. However, municipalities have very few tools to monitor the evolution of riparian zones within their territory. The objective of this study was therefore to evaluate, using a Riparian Zone Quality Index (IQBR), whether municipal regulations can lead to a measurable improvement in riparian condition. Using such an index in this specific context is novel and could help municipalities and shoreline residents identify the improvements needed to restore or maintain riparian buffers. Ultimately, the results of this study may encourage municipalities and lake associations to adopt the IQBR as a monitoring tool and integrate it into watershed management plans.

2The Policy for the Protection of Lakeshores, Riverbanks, Littoral Zones and Floodplains defines a riparian buffer as a strip of land adjacent to a lake or watercourse whose width is determined according to slope and riparian height (Ministère de l’Environnement, 1987) (Figure 1). Determining its width and composition makes it possible to assess its potential to protect the aquatic environment. If the riparian is more than 5 meters high and the slope exceed 30 degrees, the riparian buffer is considered to extend 15 meters from the high‑water mark (MUNSAR, 2007). If the riparian is less than 5 meters high and the slope is under 30%, the buffer extends 10 meters from the high‑water mark. As illustrated in Figure 1, the high‑water mark is defined as the point along the shoreline where aquatic vegetation gives way to terrestrial vegetation (MUNSAR, 2007; Barton et al., 1985). Sweet gale (Myrica gale) is an example of a shrub that can serve as a visual indicator for this boundary (MDDELCC, 2015).

3Our case study is located in the municipality of Saint‑Alphonse‑Rodriguez, which is part of the Matawinie Regional County Municipality (RCM) in the administrative region of Lanaudière. In 2007, Saint‑Alphonse‑Rodriguez adopted regulations aimed at protecting the riparian buffers of its 34 lakes as well as those bordering the Assomption River within its territory (MUNSAR, 2007). The selection of this municipality was primarily based on the availability of a budget for the present work and on the fact that we had access to the necessary tools (pictures and cartographic data) to conduct a comparative analysis between 2007 and 2023. Indeed, in 2007, the municipality taked pictures of all shoreline properties within its jurisdiction. The initial purpose of these photographs was to provide visual evidence in cases where citizens were suspected of violating riparian protection regulations. Additionally, in 2007, the RCM made cadastral subdivisions and property dimensions publicly accessible on its website. The objective of the present study is therefore to apply the Riparian Zone Quality Index (IQBR) as a monitoring tool for municipal regulations. To our knowledge, no previous study has used the IQBR calculation specifically within this context.

The Riparian Buffer Quality Index (IQBR)

4Several methods exist to assess riparian buffers, including the use of pictures and evaluation grids to estimate surface cover percentages based on various parameters, or questionnaires linked to field observations (Tripp et al., 2022; MDDEP & CRE Laurentides, 2009). In general, these approaches allow observers to visually detect whether riparian conditions are deteriorating or improving, but they do not provide a basis for standardized classification. The use of the Riparian Buffer Quality Index (IQBR), a tool developed by St‑Jacques and Richard (1998) for Québec’s Ministry of the Environment it’s an innovative alternative. This index makes it possible to semi‑quantitatively estimate the ecological condition of riparian zones and their ability to fully perform their role as transitional environments between aquatic and terrestrial ecosystems. The IQBR is calculated using the percentage cover of nine riparian components, each weighted according to its potential to fulfill specific ecological functions (Table 1).

Table 1. Weighting factors for the different riparian buffer components used to calculate the IQBR for lake of Pines.

Riparian Buffer Components	Weighting Factors	Impacts	Components Used for lake of Pines
Tree	10.0	Helps maintain the quality of aquatic and terrestrial habitats. Stabilizes the shoreline. Partially reduces solar radiation.	X
Shrub	8.2	Natural environment with a lower impact on shoreline stability and solar radiation.	X
Herbaceous	5.8	Less effective than the first two parameters in preserving riparian habitats.	X
Forest harvesting	4.3	Partially maintains shoreline stability. Contributes to water warming.	—
Rock outcrop	3.8	Provides only shoreline stability.	—
Old field, pasture, and lawn	3.0	Lawn is not an indigenous herbaceous plant. Contributes to water warming.	X
Anthropogenic infrastructure	1.9	Destruction and degradation of the natural environment.	X
Agriculture	1.9	Contributes to water warming and nutrient inputs. Degradation of terrestrial and aquatic environments.	—
Bare soil	1.7	Contributes to water warming. Does not retain nutrients.	X

5The use of the IQBR therefore makes it possible to obtain an index of the degree of integrity of a riparian zone based on criteria defined by the Ministry of Sustainable Development, Environment, and the Fight Against Climate Change (2015). IQBR measurements were grouped to classify riparian buffers from very poor

to excellent (Table 2). Using this classification provides municipalities with an overview of how their regulations influence the evolution of riparian buffers across their territory. It also offers an assessment of each individual property as well as an overall portrait for each lake.

Table 2. Definition of each class corresponding to the IQBR

Class	IQBR range
Very Poor	17-39
Poor	40-59
Average	60-74
Good	75-89
Excellent	90-100

Context and Importance of the Riparian Buffer for a Lake

6The implementation of regulations aimed at protecting riparian buffers has become necessary given the crucial role these zones play in slowing the impacts of climate warming on aquatic ecosystems (Dunn et al., 2022; BC, 2024; Barton et al., 1985). Maintaining the integrity of the riparian buffer serves four primary functions: it reduces sediment inputs and shoreline erosion, limits the influx of nutrients and pollutants, provides shading that slows water warming, and offers suitable habitat for native flora and fauna (RAPPEL, 2022).

7Climate change can affect aquatic ecosystems in multiple ways, as illustrated in Figure 2. Overall, these changes accelerate the eutrophication process in Québec’s aquatic ecosystems (Nazari‑Sharabian et al., 2018). Several of the effects shown in Figure 2 can be mitigated by the presence of an effective riparian buffer. Indeed, studies have demonstrated that the floristic composition of riparian zones plays an important role in reducing the rate at which climate‑related impacts affect aquatic ecosystems (Woolay et al., 2022; Dwire et al., 2017). According to the Regroupement des associations pour la protection de l’environnement des lacs et des bassins versants (RAPPEL, 2022), many Québec lakes have undergone significant changes since the 1950s. Results from a study conducted by RAPPEL in 1998–1999 indicate that, despite the provincial riparian protection policy implemented in 1987, more than 59% of lake shorelines were considered artificialized (RAPPEL, 2022). Natural shoreline elements have been replaced by retaining walls, rock armoring, lawns, or ornamental horticulture (RAPPEL, 2022) (Table 3). Maintaining and protecting natural riparian vegetation is therefore essential to slowing the impacts of climate change on aquatic ecosystems. However, an effective riparian buffer requires the presence of three layers of native vegetation herbaceous, shrub, and tree strata composed of species naturally occurring in the environment (Brian et al., 2002). Among the impacts shown in Figure 2, several can be influenced by riparian buffers (RAPPEL, 2026), particularly rising temperatures and episodes of strong winds.

Table 3. Comparison Between an Artificially Modified Riparian Buffer and an Undisturbed Riparian Buffer (RAPPEL, 2022)

Disadvantages of an Artificially Modified Shoreline	Advantages of an Undisturbed Shoreline
Significant erosion	Stabilization of the shoreline
Increased input of pollutants and nutrients	Limits the input of pollutants and nutrients
Water warming and associated impacts	Limits temperature increases through the creation of shaded areas
Reduced water transparency	Maintains water transparency
Increase in phytoplankton and aquatic plants	Limits the growth of phytoplankton and aquatic plants
Accelerated eutrophication rate	Reduced risk of hyper‑eutrophication

Increase in Water Temperature

8The rise in global average temperature affects various ecosystems, including aquatic ecosystems, which are sensitive to thermal variations (Kreamer, 2021; Havens & Jeppensen, 2018; Bennion et al., 2010; Shurin et al., 2012). It has been demonstrated that an increase in average water temperature will, among other effects, lead to a decrease in dissolved oxygen concentration, changes in pH, shifts in nutrient concentrations, increases in dissolved carbon dioxide, and modifications to thermal stratification (Bélair et al., 2025; Couture et al., 2012; Jane et al., 2021; Bartosiewicz et al., 2019; Arnoux, 2017). By altering environmental conditions, warmer water also allows nutrients and toxic substances trapped in sediments such as organochlorine compounds, phosphorus, and certain metals to become bioavailable (Hansen et al., 2025). These physicochemical changes can create unfavorable conditions for the survival of certain species. Salmonids, for example, are highly sensitive to dissolved oxygen concentrations (Isaak et al., 2015; Bélanger et al., 2013). Conversely, more tolerant species, such as pumpkinseed sunfish, may benefit from these altered conditions (Chauvette, 2023). However, this warming of lake water can be slowed by the presence of an effective riparian buffer (Gagnon & Gangbazo, 2007). Riparian vegetation creates shaded areas that reduce the surface exposed to direct sunlight. This reduction in sun exposed area throughout the day helps maintain cooler water temperatures (RAPPEL, 2026). Water temperature along a forested riparian buffer can be 2 to 10 °C lower compared to an unforested shoreline (FIHOQ, 2013).

Changes in the Hydrological Regime

9Climate change also induces modifications to the hydrological regime (CEHQ, 2015). In Québec, over the past few decades, average annual precipitation has increased by 10.5% across the province (Bush & Lemmen, 2019; Vincent et al., 2018). In autumn and spring, precipitation has risen by approximately 20%, and in winter by about 6% in the northern part of the province (Bush & Lemmen, 2019). In contrast, decreases in seasonal precipitation have been observed in winter in the southeast and in spring in the James Bay region (Bush & Lemmen, 2019). The increased intensity and frequency of extreme precipitation events in various regions cause rapid rises in lake water levels above seasonal norms, sometimes leading to flooding (Zhang et al., 2019). These precipitation patterns result in greater runoff, which affects entire watersheds (Duchemin et al., 2004). Runoff transports nutrients that contribute to lake enrichment, promoting the proliferation of invasive algae and potentially cyanobacteria (Larsen, 2020). It also carries particulate matter that increases turbidity (CCME, 2003). By absorbing solar energy, suspended particles influence the thermal stratification of lakes (Dufresne, 2019). Depending on their nature, these particles may also affect aquatic organisms (CCME, 2003). However, erosion and the input of nutrients and sediments into lakes can be reduced (RAPPEL, 2026). Riparian vegetation acts as a filter during runoff, limiting the introduction of pollutants and sediments (Mayer et al., 2005; Daniel & Gilliam, 1996; Dillaha et al., 1988). The root systems of riparian plants also help stabilize shorelines and reduce erosion (Gagnon & Gangbazo, 2007).

Episodes of Strong Winds

10Climate change is causing more frequent episodes of strong winds, which contribute to both chemical and physical alterations in lake environments (Jean & Frini, 2025). Waves generated by high winds can significantly erode shorelines when adequate vegetation is absent (Dulude, 2016; FIHOQ, 2013). This shoreline erosion contributes to lake sedimentation and increases the input of nutrients and potentially toxic compounds that may affect herpetofauna (Dulude, 2016). As with runoff, the root systems of riparian vegetation help stabilize shorelines and limit erosion (FIHOQ, 2013; Gagnon & Gangbazo, 2007). It is important to note that trees and shrubs provide better protection against shoreline erosion than grasses (FIHOQ, 2013).

Methodology

Selection and Description of the Study Lake

11Lake of Pines is one of the 34 lakes located within the municipality of Saint‑Alphonse‑Rodriguez. It was selected as the study site based on the available budget, the high number of shoreline property owners, its accessibility, and the willingness of residents, through the local property owners’ association to participate in the study. This natural lake covers an area of approximately 0.25 km² and is bordered by 48 properties (Figure 3). Its perimeter is roughly 2.0 km (Conseil régional en environnement des Laurentides, 2019). Like many lakes in the Laurentides region, it is a remnant of the last glaciation. Its basin reaches nearly 37 meters in depth, making it the deepest lake in Saint‑Alphonse‑Rodriguez.

12The vegetation encircling lake of Pines is characteristic of the northern zone that extends across southern Québec up to the 48th parallel. This zone is composed of two sub‑zones: the deciduous forest and the mixed forest. The vegetation surrounding lake of Pines corresponds to the deciduous forest sub‑zone (MRNFQ, 2022). This area is dominated by maple–beech stands, featuring sugar maple (Acer saccharum), American beech (Fagus grandifolia), yellow birch (Betula alleghaniensis), as well as conifers such as eastern hemlock (Tsuga canadensis) and eastern white pine (Pinus strobus) (MRNFQ, 2022). Occasional populations of northern white cedar (Thuya occidentalis), fir tree (Abies balsamea), white spruce (Picea glauca), and black spruce (Picea mariana) may also be found. Considering the type of vegetation present in the surrounding environment is essential when aiming to accelerate riparian buffer regeneration through planting efforts.

Calculation of the Riparian Zone Quality Index (IQBR)

13The reference year for calculating the IQBR is 2007, for two reasons. First, 2007 marks the initial implementation of regulations targeting riparian protection zones in the municipality of Saint‑Alphonse‑Rodriguez. Second, it is also the first year for which suitable pictures and the necessary digital and cartographic tools were available to perform the IQBR calculation.

14The IQBR was assessed for each of the 48 shoreline properties around lake of Pines. Among these 48 properties, we also included lake access points belonging to second‑row properties, as well as the various sides of the island (Figure 3).

15The IQBR was calculated for each of the two study years, 2007 and 2023. The parameters used to compute the riparian buffer quality index for lake of Pines reflect the ecological reality of the site. Indeed, there is no forest harvesting, exposed bedrock, or agricultural activity within the riparian zone of lake of Pines (Table 1). For this reason, we retained six of the nine components, along with their associated weighting factors established by St‑Jacques and Richard (1998) (Table 1). These weighting factors were derived from the ratio between the actual ecological potential and the maximum potential of each component with respect to the preservation of riparian ecological functions (St‑Jacques & Richard, 1998). Thus, the presence of a well developed tree layer increases riparian quality, with a maximum weighting factor of 10. Conversely, the presence of a concrete retaining wall reduces riparian quality, as the weighting factor associated with this component is 1.9 (Table 1). The IQBR assessment for each property was carried out in three steps.

Step 1. Calculating the riparian buffer area

Step 2. Calculating the area of each component

17The percentage of surface area occupied by each of the six components was determined using orthophotos from the Matawinie RCM, Google Maps, and in‑situ pictures from 2007 and 2023. Electronic measurement tools from the RCM’s mapping service and Google Maps were used to estimate surface area percentages. In addition to these techniques, a spreadsheet based grid overlay improved measurement precision (not shown).

18These measurements are semi‑quantitative and provide an the riparian buffer area occupied by the different parameters estimate. Pictures of each property from 2007 and 2023 were also used to validate the presence of the various components. The methodology is similar to that used for assessing the riparian buffer quality index of the Etchemin River (BGE, 2017).

Illustration of the methodology

19In Figure 3, the red point indicates the property used as an example for the IQBR calculation. Figures 4 through 7 illustrate an example of the application of the methodology.

Step 3. IQBR Calculation

20The following formula was applied: IQBR = (Σ (%C × Pc)) / 10, where %C is the percentage of the area occupied by the component (value between 0 and 100), C represents the components (trees, shrubs, lawn), and Pc is the weighting factor.

21The calculation was performed for each shoreline property. The resulting value was then compared with the evaluation grid to classify the capacity of each property’s riparian buffer to fulfill its ecological functions. Table 2 presents this classification, established by Québec’s Ministry of the Environment, the Fight Against Climate Change, Wildlife and Parks (MELCCFP, 2015).

Statistics

22First, we calculated the mean and standard deviation of the percentage occupied by each of the six parameters across the entire riparian buffer. Then, to obtain an overview of the lake wide IQBR, we summed the indices of all properties and computed the arithmetic mean and standard deviation to compare the years 2007 and 2023. A Student’s t‑test (n = 48) was performed to determine whether the differences between 2007 and 2023 were statistically significant.

Results and Analysis

23Figure 8 provides an overview of the relative importance of the percentage cover associated with each of the six riparian components. Between 2007 and 2023, a very slight decrease in the percentage of bare soil is observed. The figure also shows that the percentage of cover by anthropogenic structures has remained essentially unchanged. This stability is explained by the fact that human-made structures mainly concrete retaining walls and residential buildings were built prior to the implementation of riparian regulations and have remained in place. This stability also indicates that no new constructions have been added within the riparian buffer. These parameters therefore do not contribute to variations in IQBR between 2007 and 2023, although their ecological impact remains significant.

24In contrast, Figure 8 shows clear changes in vegetation cover. In 2007, lawn surfaces were predominant, covering approximately 35% of the lake’s riparian buffer. By 2023, this proportion had decreased to about 20%, a reduction of nearly 15%. Over the same period, the areas occupied by the different vegetation strata increased: by roughly 4% for trees, 10% for shrubs, and 3% for herbaceous vegetation. In 2007, some properties had up to 62% of their riparian buffer covered by lawn. In 2023, the maximum lawn cover had decreased to about 42%. Figure 8 shows that the shrub layer experienced the greatest increase between 2007 and 2023, with nearly 10% more coverage. This trend may be explained by the fact that shrub vegetation typically establishes itself before the tree layer during ecological succession (Ramade, 1984). The increase in this shrub layer would gradually influence access to sunlight, thereby helping to control the herbaceous layer. This competition for light, as well as for nutrients, would act as a limiting factor for herbaceous plants, which explains why this vegetation stratum occupied only about 4% of the riparian buffer surface in 2023 (Figure 8).

25These variations in the percentage of cover among the different vegetation strata modify the distribution of IQBR values across the various classes (Figure 9). We indeed observe a substantial reduction in the proportion of riparian buffers that, in 2007, had an IQBR falling within the very poor and poor classes representing a total of 57% which declined to 10% in 2023. Conversely, the total percentage of properties with an IQBR in the moderate, good, or excellent classes increased from 43% in 2007 to 90% in 2023. It is also worth noting that the proportion of riparian buffers classified as excellent doubled, rising from 12% in 2007 to 24% in 2023.

26Due to changes in riparian vegetation between 2007 and 2023, the mean IQBR increased from 59 to 76 (Figure 10). The Student’s t‑test yielded p < 0.0001, indicating a highly significant difference between the 2007 and 2023 results. Overall, the riparian buffer improved from poor to good condition (Figure 10). The visual comparison between Figures 4 and 5 provides a clear example of the improvement in IQBR between 2007 and 2023.

27This overall improvement in the riparian buffer can be explained, among other factors, by the reduction in lawn-covered areas and the expansion of herbaceous, shrub, and tree strata (Figure 8). The increase in the surface area occupied by the latter two strata contributes directly to higher IQBR scores and therefore to an improved classification. These two parameters indeed have the highest weighting factors 8.2 for the shrub layer and 10 for the tree layer reflecting their ecological importance within a riparian buffer.

Discussion

28Urbanization has significantly altered the natural vegetation cover of riparian zones. Studies have shown that the urbanization of riparian buffers, combined with climate warming, accelerates processes that can disrupt aquatic ecosystems (Charron et al., 2010; Gagnon & Gangbazo, 2007; Desjardins, 1995; Belt et al., 1992). It is important to note that a substantially degraded riparian buffer will be less effective at retaining nutrients during heavy rainfall events (Dunn et al., 2022). In addition, increased nutrient bioavailability may also result from warmer water temperatures, which enhance the dissolution of nutrients present in the aquatic environment (Dunn et al., 2022). These combined phenomena can stimulate the growth of native plants but also of invasive species and cyanobacteria, to the detriment of existing flora (Kosten et al., 2011; MDDEP & CRE Laurentides, 2009; MDDEP & CRE Laurentides, 2007). All these ecosystem changes create conditions that accelerate eutrophication processes (Woolway et al., 2022).

29Given the impacts of climate change on lakes, shoreline property owners have relatively few mitigation measures at their disposal to slow these effects. One of the most important actions they can take is to comply with regulations aimed at maintaining the integrity of riparian buffers. As previously discussed, these buffers play multiple ecological roles (Woolway et al., 2022; Nazari-Sharibian et al., 2018; Jeppesen et al., 2014; Hickey & Doran, 2002; Desjardins, 1995).

30Regulatory compliance allows riparian vegetation to help modulate the warming of lake water induced by climate change. However, the influence of vegetation on water temperature depends on several factors. The morphometric characteristics of the lake must be considered (Bélanger et al., 2013), as well as the nature of the lakebed substrate (Fang & Stefan, 1996). Rocky, sandy, silty, or detritus-covered substrates absorb and release solar energy differently. Another key factor is the average height of the vegetation within the riparian buffer. Herbaceous vegetation provides limited shading and therefore has a weaker effect on reducing water temperature. In contrast, the tree layer can shade larger portions of the lake depending on the sun’s position throughout the day. Time of day and sun angle create uneven heating patterns. For example, the north-facing shore of a lake is typically exposed to maximum solar radiation between 11 a.m. and 2 p.m., resulting in peak warming, while the opposite shore may remain shaded by tall trees and thus experience less warming. Together, these factors influence the daily solar energy input and contribute to moderating water temperature, with wind further aiding this regulation. The structural characteristics of riparian vegetation are therefore essential for maintaining thermal stability in aquatic ecosystems, underscoring the importance of regulatory compliance. According to FIHOQ (2013), riparian buffer width is less critical for maintaining lower water temperatures than vegetation height, density, and orientation.

31Pictures of riparian buffers and their vegetation taken by the municipality in 2007 are valuable tools for visually assessing regulatory compliance in subsequent years. However, they provide only a subjective indication of improvement when compared with more recent photographs, such as those from 2023 (Figures 4 and 5). For instance, if pictures reveal that a tree was cut in a forested riparian buffer to create lake access, one must consider how this affects ecological integrity compared with cutting the only tree present in a lawn-dominated buffer. The present study demonstrates that using the IQBR allows for such evaluations.

32The IQBR results for the riparian buffers of lake of Pines show a clear overall improvement since the implementation of the regulation in 2007. These results also help residents identify actions that could further improve riparian buffer quality in the coming years for example, reducing lawn surface area. Improvements in IQBR scores at the property level contribute to the overall enhancement of the riparian buffer, and these targets can be integrated into a watershed management plan.

Conclusion

33Climate change has already begun to affect aquatic ecosystems in Québec. For shoreline residents, one of the most effective ways to slow these impacts is to ensure that their riparian buffer can fully perform its ecological functions by complying with regulations. This study demonstrates that the IQBR is an excellent tool for municipalities wishing to evaluate the effectiveness of their regulations on riparian buffer evolution.

34The results also show that there remains room for improvement in the riparian buffer quality of lake of Pines. This improvement depends on the willingness of shoreline property owners to gradually comply with regulations. Each owner can set their own IQBR improvement target over time. For example, a property owner might decide to reduce lawn cover in their riparian buffer by 20% within five years simply by ceasing mowing. Integrating such improvement targets into a lake’s watershed management plan can foster a shared community and environmental objective. Continued community involvement and regulatory compliance are essential to reducing climate related pressures on aquatic ecosystems. For this reason, regular monitoring using the IQBR will be necessary to flow riparian buffer evolution in the coming years.