In EffetsCumulatifsNavigation/ceanav: Research compendium for project on the assessment cumulative effects of marine vessel activities in the St. Lawrence

Cumulative effects {#cearesult}

The method used to obtain the following results is presented in section \@ref(ceamethod) of the report.

The main result of the assessment applies the overall cumulative effects assessment model by including the distribution and intensity of environmental stressors, the distribution of valued components, and the vulnerability of valued components to environmental stressors. The presentation of the results of the overall model has thus already been initiated by exploring the results of the partial models (see sections \@ref(strcumresult), \@ref(cvcumresult) and \@ref(cumexpresult)). By including the vulnerability of valued components to the environmental stressors, the overall model allows for modulation of the intensity of the predicted cumulative effects; thus, the distribution of cumulative effects may be similar to that of cumulative exposure, but the relative intensity of the predicted effects may be greater or lesser depending on the vulnerability of the valued components (see section \@ref(method) for more details).

The results of the cumulative effects assessment reveal that the environments most affected by environmental stressors are similar to those identified by the cumulative exposure assessment (Figures \@ref(fig:cumExp) and \@ref(fig:cumEffects)); a similar interpretation can therefore be made regarding the spatial distribution of cumulative effects. The valued components are at risk for cumulative effects of marine activity-related environmental stressors throughout the study area. The environments most at risk from cumulative effects of marine vessel activities are those with a greater overlap of valued components (Figure \@ref(fig:cvCum)) and environmental stressors (Figure \@ref(fig:stCum)).

Within the fluvial sector, the Quebec City and southern Île d’Orléans regions, as well as the entire shipping channel between Trois-Rivières and Montreal, including Lake St. Pierre, are particularly at risk; the mouth of the Saguenay River is the marine sector region most affected by stressors related to marine vessel activities (Figure \@ref(fig:cumEffects) and \@ref(fig:cumEffectsPanel)). In terms of valued components, these environments display a significant diversity of habitats and areas of interest, as well as areas where bank integrity is at risk from marine vessel activities throughout (Figure \@ref(fig:cumEffectsPanel) and \@ref(fig:cvPanel)). These environments are also subject to a wide variety of high-intensity environmental stressors (Figure \@ref(fig:stPanel))

Within the marine sector, predicted cumulative effects are broadly distributed at low intensity (Figure \@ref(fig:cumEffects)). Only the mouth of the Saguenay River shows more intense cumulative effects (Figure \@ref(fig:cumEffects)) which are largely dictated by the effects of shipping on marine mammals that frequent this region of the study area (Figure \@ref(fig:cumEffectsPanel)). In addition to marine mammals, several areas of interest were also identified in this region (Figure \@ref(fig:cumEffectsPanel)).

knitr::include_graphics("./figures/figures-output/cumulative_effects.png")

knitr::include_graphics("./figures/figures-output/cumulative_effects_panel.png")

Pathways of effect

st <- read.csv("../data/data-metadata/metadata_stresseurs.csv")
cv <- read.csv("../data/data-metadata/metadata_composantes_valorisees.csv")

The proposed cumulative effects assessment theoretically allows for the exploration of all combinations of stressors and valued components included in the assessment. Considering the r nrow(st) categories of stressors and the r nrow(cv) categories of valued components, there are nearly 2,000 possible pairs; these pairs form the set of direct pathways of effect that environmental stressors can take to affect valued components. A pathway of effect links activities to their potential impacts on various aspects of the ecosystem [@dfo2020d].

Although we cannot explore all of these area of interest within this report, Figures \@ref(fig:metanetwork) and \@ref(fig:ceakm) provide a visual representation of all of these combinations and the contribution of stressors to the total cumulative effects predicted for each valued component considered. The total effects of environmental stressors on valued components were assessed by the sum of the effects divided by the total area of the valued component on which an effect is predicted. For example, if a habitat with an area of 2 $km^2$ is affected by two stressors with predicted effects of 0.25 and 0.75, respectively, the total effect on the valued component is 0.5 $km^{-2}$. The greater the spatial distribution of a stressor, the greater its total effect is likely to be; similarly, total effects are likely to be greater the less widely distributed a valued component is.

cekm <- read.csv("../data/data-output/cumulative_effects_cv_km2.csv") %>%
        select(-cv, -area, -cea) %>%
        as.matrix()
uid <- cekm > 0
npof <- sum(uid)
mpof <- round(mean(cekm[uid]),2)
spof <- round(sd(cekm[uid]),2)

The figure \@ref(fig:metanetwork) visualizes the set of predicted direct area of interest within the cumulative effects assessment. The links represent the presence of a predicted effect of a stressor on a valued component. The size of the points represents the total predicted effects on the valued components or originating from the environmental stressors. It is important to note that this figure should not be interpreted in detail; rather, it provides an at-a-glance view of the amount of information available within the cumulative effects assessment conducted. There are r npof direct area of interest with an average relative effect of r mpof $\pm$ r spof, considering that the maximum possible relative effect is 1 based on our assessment method.

Figure \@ref(fig:ceakm) complements Figure \@ref(fig:metanetwork) and makes it possible to explore the area of interest in more detail by presenting the relative contribution of each stressor to the predicted effects for each valued component. The significant effects of shipping and marine pollution on all valued components considered are noted. These results are expected since these stressors are the most prevalent among those considered for the assessment. Commercial fisheries affect certain valued component categories more intensively, such as many sites of interest, habitats of the fluvial sector and mollusk beds in the marine sector. Commercial fisheries in the fluvial sector seem to have a greater global effect than that of commercial fisheries in the marine sector, likely due to the smaller spatial extent of the fluvial sector compared to that of the marine sector. In general, the other environmental stressors have smaller total effects, except for commercial fisheries, which affect some categories of valued components more intensely, such as mollusk beds and some cultural, heritage and archeological areas of interest. The lower total effects can be explained by the more ad hoc distribution of other environmental stressors within the study area.

Cultural, heritage, and archeological areas of interest are the most exposed to the effects of marine activity-related stressors. It should be noted, however, that all areas of interest were considered vulnerable to all environmental stressors; as such, a spatial overlap between a stressor and an area of interest was sufficient to identify a pathway of effect. This means that a comparison between total effects on areas of interest and other valued components should be avoided, or at least take into account the maximum vulnerability attributed to areas of interest. Nevertheless, this is an important result that is informative about the exposure of areas of interest to marine vessel activities in the study area.

In addition to areas of interest, bank integrity is the most affected valued component, primarily by shipping and to a lesser extent, by dredging activities. Total habitat effects vary by habitat type, although habitats are affected by a wide variety of environmental stressors.

Finally, the least affected valued component is marine mammals. However, it is important to remember that these species cover a very large area and accordingly, the assessment per $km^2$ underestimates the predicted cumulative effects scores. An analysis specifically targeting the critical environments of these species would undoubtedly increase the total predicted effects on marine mammals. It is also important not to downplay the cumulative effects on marine mammals since one of the areas at greatest risk of cumulative effects from marine vessel activities is at the mouth of the Saguenay River due to the significant presence of marine mammals (Figures \@ref(fig:cumEffects) and \@ref(fig:cumEffectsPanel)).

knitr::include_graphics("./figures/figures-output/cumulative_effects_metanetwork.png")

knitr::include_graphics("./figures/figures-output/cumulative_effects_regional_contribution.png")

Administrative regions

A cumulative effects assessment by $km^2$ of the 11 administrative regions [@mern2021b] separating the study area was also conducted to explore regional differences in the intensity of the cumulative effects (Figures \@ref(fig:regionadmin) and \@ref(fig:regionadminpanel)). The overall assessment combining all the valued components reveals that the administrative regions of the fluvial sector are much more at risk from the cumulative effects of marine vessel activities, while the marine sector seems less at risk. The Montérégie in particular seems to be the region most impacted by the effects of marine vessel activities. These observations are due to the concentration of marine vessel activities within a much narrower corridor within the fluvial sector compared to the marine sector. While this observation is not surprising, it does suggest that an increase in marine traffic in the marine sector may have disproportionate impacts in the fluvial sector if that traffic moves to the Great Lakes. This means that an additional vessel going through Quebec City cannot be interpreted in the same way as an additional vessel in Montreal. Commercial fisheries are also important is the fluvial sector, particularly for the Centre-du-Québec, Lanaudière and Mauricie regions. By extension to shipping, marine pollution is also an important stressor for the administrative regions of the fluvial sector. The types of vessels with the most significant effects are those related to the transport of goods (e.g. oil tankers, dry cargo, freighters and container ships). Government vessels also appear to have the potential to negatively affect the valued components in the study area, likely due to less constrained waterway routes and thus more widespread, lower intensity activities throughout the study area. The government and research shipping category, however, is composed of a significant diversity of vessel types, including military craft, patrol vessels, and scientific research vessels. This diversity increases the uncertainty with regard to how vulnerable the valued components are to this type of shipping, and accordingly, to the predicted effects.

knitr::include_graphics("./figures/figures-output/cumulative_effects_region_cea.png")

knitr::include_graphics("./figures/figures-output/cumulative_effects_region_cea_panel.png")

EffetsCumulatifsNavigation/ceanav documentation built on April 17, 2023, 1:02 p.m.