Impacts of Climate Change and Physical Barriers to Coastal Squeeze in the Gulf and Estuary of the St. Lawrence River, and an Assessment of Adaptation Measures

Coastal ecosystems in Canada are under stress from two sources. The combined effects of increasing urbanization along the coast and climate change  can lead to the degradation of these ecosystems and sometimes even their loss.

In zones subject to accelerating sea level rise, physical barriers such as dead cliffs (resistant to erosion), infrastructure (roads or homes) along the coast, and rigid coastal protection structures can interfere with the natural adjustment of coastal ecosystems.

This significantly reduces the space available to coastal ecosystems to migrate landward. This phenomenon, known as coastal squeeze, will accelerate as the climate changes and/or the rate of construction along the coastline continues to increase.

Photo : P. Bernatchez (UQAR)

• Assess the combined impact of climate change and human activities on the evolution of coastal ecosystems in the Gulf and Estuary of the St. Lawrence River  in Quebec and New Brunswick over the 2100 time horizon.

• Examine potential solutions for reducing the impacts.

• Draw a portrait of current and future coastal habitat vulnerability to coastal squeeze for the Gulf and Estuary of the St. Lawrence River.

• Produce an assessment of the changes to representative Gulf and Estuary of the St. Lawrence River coastal ecosystems over the past 50 years and identify the causes of these changes.

• Identify the ecological services provided by coastal ecosystems and the species at risk.

• Simulate, with the help of models, probable changes to the coastal ecosystems under plausible climate change and sea level rise scenarios, taking into account human disturbances.

This initial portrait of the distribution of coastal ecosystems across the GESL reveals that the phenomenon of coastal squeeze is a source for concern. Indeed, about half of the surface area of the ecosystems studied is likely to be susceptible to coastal squeeze by the year 2060.

Shoreline development and increasing artificialization of the coastline cause coastal ecosystems to be trapped between the built environment and rising sea levels (Figure 1).

A retrospective analysis of nine local and regional sectors reveals variable changes in coastal ecosystem area over the past 50 years, with both gains and losses in area depending on the sector. In the case of loss of natural areas such as beaches, marshes and sand spits, the consequences can be felt in coastal communities; especially as these ecosystems play an important role on both land and sea by providing several ecological services that benefit human well-being and safety, including natural protection against erosion and coastal submersion (Figure 2).

The analyses reveal the importance of coastal ecosystems that provide ecological services for many plant and animal species as well as for humans.

These ecosystems are particularly vulnerable to climate change, and the current coastal land use and development model is proving to be extremely damaging to these important environments.

To counter coastal squeeze and its potential impacts, the study recommends the following measures: Identify and protect resilient ecosystems close to urban areas in order to prioritize their conservation: such sites are likely to be exposed to urban development in the near future, which could reduce their resilience; Preserve buffer zones allowing ecosystems to migrate landward; Limit urbanization to prevent ribbon development close to the shoreline; Raise awareness of coastal squeeze among the population and policy-makers; Improve the sustainable integrated management of the littoral zone in order to harmonize adaptation and sustainable development actions in coastal areas.

• New Brunswick Department of Natural Resources

• Ministère de la Sécurité publique du Québec 

• Ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques

• Ministère des Transports du Québec

• Parks Canada

• Moncton University 

• Université du Québec à Rimouski

• Université du Québec à Montréal