L’évaluation des impacts cumulés dans l’estuaire et le golfe du Saint-Laurent : vers une planification systémique de l’exploitation des ressources

Abstract

L’intensification de l’empreinte humaine dans l’estuaire et le golfe du Saint-Laurent impose une planification systémique de l’exploitation des ressources marines. Une évaluation régionale des impacts cumulés dans le Saint-Laurent demeure pourtant encore attendue. Un nombre important d’activités (p. ex. transport maritime, pêche, aquaculture) caractérise l’exploitation humaine du Saint-Laurent. Ces activités imposent plusieurs stresseurs environnementaux (p. ex. destruction de l’habitat) affichant un chevauchement spatial croissant. Individuellement, ils peuvent affecter la structure et le fonctionnement des écosystèmes. Imposés simultanément, les stresseurs peuvent agir en synergie et entraîner des effets non linéaires imprévisibles. Ces effets demeurent largement incompris et conséquemment ignorés lors d’évaluations d’impacts environnementaux, qui demeurent orientées sur des espèces ou secteurs uniques et l’approbation de projets. Plusieurs défis relatifs aux impacts cumulés dans le Saint-Laurent doivent être relevés : 1) améliorer l’état des connaissances des impacts de multiples stresseurs sur les écosystèmes, 2) améliorer l’applicabilité des méthodes d’évaluation d’impacts cumulés, 3) identifier des indicateurs d’impacts cumulés, 4) créer un protocole de suivi environnemental et d’impacts humains, et de partage de données et 5) développer une capacité de gestion adaptative pour le Saint-Laurent. La planification systémique de l’utilisation des ressources naturelles au sein du Saint-Laurent nécessitera une vision intégrative de la structure et du fonctionnement des écosystèmes ainsi que des vecteurs de stress qui leur sont imposés. Une telle approche ne sera réalisable que lorsque nous aurons développé les infrastructures et les outils nécessaires à une gestion écosystémique du Saint-Laurent.The intensification of human activity in the Estuary and Gulf of St. Lawrence (Canada) imposes the need for a systematic planning approach for the use of marine resources. There is, however, currently no regional cumulative impact assessment for the St. Lawrence. Many of the human activities in this area (e.g., shipping, fisheries and aquaculture) impose environmental threats (e.g., habitat destruction) that may jeopardize ecosystem structure and function. Increasingly, these threats are overlapping spatially, which induces synergies causing unpredictable non-linear effects on ecosystems. These effects are still poorly understood and consequently neglected in environmental impact assessments, which remain focused on single species or sectors, and on the approval of specific projects. To efficiently evaluate cumulative impacts in the St. Lawrence, it will be important to: 1) improve our knowledge concerning the impacts of multiple threats to ecosystems; 2) improve the accessibility to, and the applicability of, cumulative impact tools; 3) identify relevant human and environmental indicators of cumulative impacts; 4) create a data sharing, and human impact and environmental monitoring protocol; and 5) develop an adaptive ma...

On the sensitivity of food webs to multiple stressors

“…(b) Magnitude of simulated trophic sensitivities as a function of the number of ecological processes included in a pathway of effect ecological communities (El-Sabh & Silverberg, 1990;Savenkoff et al, 2000). The St. Lawrence System also provides a wealth of ecosystem services; it sustains rich commercial fisheries, grants access to one of the most densely populated regions in North-America through more than 40 ports, is home to an expanding aquaculture production and has an expanding tourism industry (Beauchesne et al, 2016;Archambault et al, 2017;Schloss et al 2017). These human-induced stressors blend with climate-related stressors that result in intricate cumulative exposure regimes across the St. Lawrence System (Beauchesne et al, 2020).…”

Ecological interactions amplify cumulative effects in marine ecosystems

“…The code used to predict species interactions is available at https://github.com/david-beauchesne/Predict_interactions (DOI: ) and https://github.com/davidbeauchesne/Interaction_catalog (DOI: ), and described in. 30 The code used to predict the St. Lawrence metaweb is available at https://github.com/david-beauchesne/MetawebEGSL (DOI: ). The code to evaluate species-speci c sensitivities is available at https://github.com/davidbeauchesne/Species_Vulnerability (DOI: ).…”

“…Here, we expand conventional cumulative effects assessment approaches (hereafter, species-scale assessment) [25][26][27] with recent Page 3/24 progress in theoretical ecology 14,28,29 to propose a novel method to capture the indirect propagation of the effects of stressors through species interactions (hereafter, network-scale assessment).We focus our network-scale assessment on the St. Lawrence marine ecosystem, in eastern Canada (see methods). This ecosystem is formed by one of the largest estuaries in the world and a vast interior sea.Together, they host diverse and productive ecological communities and provide a wealth of ecosystem services bene ting the Canadian economy: a rich commercial sheries industry, a seaway that grants access to one of the most densely populated regions in North-America and more than 40 ports, an expanding aquaculture production, and a thriving tourism industry 30,31 .We demonstrate our approach by assessing and mapping the cumulative effects of 18 stressors on 193 species between 2010 and 2015. We use data-based or theoretically-derived indicators to characterize the distribution and intensity of stressors 32 , the distribution of species, the network of species interactions, and species-speci c sensitivities to stressors; these are then combined through a theoretical framework 14 to predict a cumulative effect score for every species considered (see methods).…”

Characterizing Exposure to and Sharing Knowledge of Drivers of Environmental Change in the St. Lawrence System in Canada

“…In the face of uncertainty and in an effort to address impending environmental changes, adaptive management has been identified as the chief strategy to guide efficient decisionmaking (e.g., Margules and Pressey, 2000;Keith et al, 2011;Jones, 2016;Chion et al, 2018) and has already been discussed in the context of multi-drivers and cumulative impact assessments (Halpern et al, 2015b;Beauchesne et al, 2016;Côté et al, 2016;Schloss et al, 2017). Adaptive management can only be truly achieved through a commitment to adaptive monitoring and data reporting (Margules and Pressey, 2000;Halpern et al, 2012;Lubchenco and Grorud-Colvert, 2015).…”

“…As a result, the St. Lawrence System has benefited the Canadian economy. It sustains a rich fisheries industry targeting more than 50 species, serves as the gateway to eastern North-America by granting access to more than 40 ports and is the most densely populated Canadian region, hosts a booming tourism industry and an expanding aquaculture production, fosters emerging activities, and boasts a yet untapped hydrocarbon potential (Beauchesne et al, 2016;Archambault et al, 2017;Schloss et al, 2017). With major investments recently made and more forthcoming in economic and infrastructure development and research (e.g., Government of Québec, 2015;RQM, 2018), an intensification of the human footprint is likely in the St. Lawrence System.…”