Assessing and Enhancing Coastal Wetland Resilience to Climate Change
By David Sweetnam, Executive Director of Georgian Bay Forever
Georgian Bay Forever is part of an important Environment and Climate Change Canada (ECCC) project to protect our globally unique and important coastal wetlands. These wetlands help to keep our water clean and provide food and shelter for migrating birds, fish, turtles, and numerous threatened or endangered species who call Georgian Bay home.
The three key questions the ECCC project has set out to address are: wetland resilience of what, to what and how can we build it? In more detail: Identifying the wetland values, processes, and services at risk and how to protect them, exploring the climate change drivers, plausible climate change impact scenarios, wetland vulnerabilities, and impacts/consequences and developing best practices, adaptive measures and strategies to enhance wetland resilience, and the types of adaptation related to resilience to allow our wetlands to resist, recover, and transform.
In her 2020 report to the ECCC entitled “Assessing and Enhancing Coastal Wetland Resilience to Climate Change: Focus Group Discussions”, Linda Mortsch points out that “wetlands are crucially significant locally, provincially, and federally as well as internationally with respect to migratory birds or RAMSAR sites, for example.The RAMSAR organization and treaty is the oldest of the modern global intergovernmental environmental agreements. The Convention's mission is “the conservation and wise use of all wetlands through local and national actions and international cooperation, as a contribution towards achieving sustainable development throughout the world”. (Read a GBF/RAMSAR article about protecting wetlands from an invasive plant Phragmites.)
Many coastal wetlands are large and provide disproportionately higher quality habitat than inland wetlands. Wetland-supported activities such as recreating, birding, nature viewing, and waterfowl hunting offer broad economic benefits. Moreover, wetlands functioning as “natural” or green infrastructure -- shoreline erosion protection, flood mitigation, water quality improvement -- avert losses and/or reduce capital costs. The most frequently cited negative consequence of not protecting resilience was habitat or biodiversity loss. Economic losses (infrastructure, property values) and exacerbation of erosion followed.”
Coastal wetlands in Georgian Bay have evolved over thousands of years since the glaciers melted away leaving behind the crystal-clear waters of the Great Lakes that we still see in the outer waters of Georgian Bay today. Don’t let anyone tell you that our wetlands are threatened by being pushed against rock shorelines or that the trees and bushes that grew lakeward at times of low-water levels but are now flooded and drowned are enemies to these dynamic spaces. High water levels help to create new habitats by flooding marginal forests and killing trees that provide excellent habitat when they ultimately succumb to the prevailing winds and topple into the water providing structure. What image of a wetland is complete without a family of turtles sunning on a fallen log? In fact, wetland restoration experts commonly rely on adding such root-wads and logs to provide habitat to protect young fish fry.
Wetlands rely on these changing conditions to stay healthy. In fact, in its review of the regulation plan for Lake Ontario the International Joint Commission determined that the water level regulation on Lake Ontario had reduced variability to the point where the coastal wetlands all degraded to cattail marshes.
Our globally unique, high-quality wetlands have evolved in the places we find them today because conditions are satisfied for a wide variety of plants and animals to thrive. They are filled with a profusion of plants and animals suited to rises and falls of the recorded 6.33 feet variability we experience in Georgian Bay and while wetlands react individually to the local conditions they experience, the numerous wetlands on Georgian Bay collectively are not adversely impacted within that historic water-level range. In our 2016 NASA report on the impacts of water levels in Georgian Bay on our coastal wetlands, we saw proof that as water levels declined from 1987 to 2013 there was actually an increase in wetlands of 7% in the northern parts of Georgian Bay but a decline of 10% in the southern portions of the Bay (development in the south over that time may also have increased that adverse impact).
But these precious, biodiverse spaces have been under increasing pressure for the past two centuries as bad business practices, development and economic exploitation have dominated public policy. But since the implementation of the Great Lakes Water Quality Agreement signed first in 1972 and renewed in 2012, public policy has changed.
More alarmingly in recent history, the driving conditions necessitating this study arise from the measurably increasing impacts of anthropogenic climate change on the global and regional ecosystems and the uncertainty this poses for the health of our precious wetland ecosystems. Canada has experienced almost double the global average temperature increase and that is resulting in: increasing storm intensities and record rainfalls; more volatile and extreme (high and low) water levels; higher wind speeds, increasing wave energies resulting in erosion, run-up flooding and infrastructure damage; and increasing surface water temperatures, and declining ice coverage in Georgian Bay, our Great Lakes and across the entire country.
Mortsch elucidates that “the aim of the project is to reduce vulnerability and to maintain and increase resilience of ecosystems and people. From an ecological perspective, resilience represents a tendency to maintain integrity when subject to disturbance.” Mortsch clearly explains that “a resilient ecosystem can cope with a hazardous event, trend or disturbance, responding or reorganizing in ways that maintain its essential function, identity, and structure, while also maintaining the capacity for adaptation, learning, and transformation.”
“An ecosystem’s resilience is shaped by its adaptive capacity: the ability or potential of species or a system to respond successfully to climate variability and change,” notes Mortsch going on to point out that “internal factors such as wetland functions, structure, components, and processes influence this capacity as well as external influences such as human stresses, disturbance regimes, and size and complexity of the ecosystem.”
This project supports the ECCC Great Lakes Protection Initiative’s Program to understand and model wetland response to water level changes associated with climate change scenarios. This is where GBF is helping out. GBF has been collecting high-resolution bathymetry and side scan sonar imagery at four selected wetlands. These locations are representative of coastal wetlands along the eastern coast of Georgian Bay in the granite archipelago.
Aided by the extreme high-water levels over the past summer, GBF has been able to get our sonar outfitted Baykeeper into wetlands that just seven years ago would have been high and dry. The imagery collected has been sent to ECCC for incorporation into their digital elevation models. These models can then be used to examine how climate change and the rise and fall of waters along our coasts will impact the wetland inventory and functions.
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Top: Treasure Bay, Bottom Left: Locations of Interest, Bottom Right: Isobath Image of Treasure Bay
Wetland Structure
Wetlands have a number of zones defined by water levels and populated by different type of plants. There are three main zones: aquatic (submergent and emergent plants), riparian (dense emergent and wet meadow plant types) and upland (including fringing forest).
And don’t forget that the real magic of our wetlands occurs in the soils where a suite of bacteria and microorganisms filter and process the nutrients coming from upstream to cleanse the waters and make them pure.
Starting furthest from shore is the submergent zone. The plants that grow at the depth of this zone depend on light penetration and the type of substrates available on the lake bed. Next, we have the floating zone where plants we all know like lily pads mix with the submerged plants and send up long shoots to floating leaves and flowers. Next, we have the emergent zone where plants like bulrushes and cattails rooting in the bottom but protruding through the surface flourish. Next, we find the wet meadow along the shore with sweet gale and grasses, that proliferate when this zone is seasonally inundated with water. And finally, we move into the shrubs and fringe of forest that surround the wetlands where moisture loving or moisture tolerant grasses, bushes and trees like tamarack ring and shield the wetlands.