Riparian buffer zone
A riparian buffer zone is a strip of vegetation several metres wide that stretches along a shoreline. Wetlands (marshes, wet meadows and swamps) form on fairly flat parts of it. Elsewhere, the zone may include forests, fields and meadows.
|A natural riparian buffer zone is essential to man because it:|
|Creates a zone where floods can be effectively absorbed ;|
|Filters water by holding back sediment and toxic substances ;|
|Provides food and shelter for many animal species ;|
|Provides opportunities for leisure activities, such as hunting, fishing and birding ;|
|Provides resources of all kinds (e.g., cranberries, fish, waterfowl, peat and wood) ;|
|Prevents shoreline erosion since the roots of buffer zone plants hold the soil in place.|
In their natural state, the shorelines of lakes and rivers are divided into several zones of vegetation. Each zone is characterized by specific water conditions and by plants species adapted to those conditions. Starting inland, the wetlands that you may encounter are tree swamps, shrub swamps, wet meadows, marshes and aquatic vegetation beds. Depending on the slope and soil, the transition from one zone to the next may cover only a small area or not exist at all.
At least 30% of a swamp’s area is covered by trees (e.g., silver maple or red ash) or shrubs (e.g., willow, dogwood or alder). When trees dominate, it is called a “tree swamp” and when bushes dominate, a “shrub swamp”.
Swamps generally occur in floodplains and poorly drained environments. They are characterized by saturated soils that are covered by water during floods or heavy rainfalls. Water sporadically withdraws, allowing the soil to dry out and aerate, thus allowing the growth of woody plant species.
Swamps are places suitable for breeding birds, fish and amphibians. Wetlands are visited by perch, pike, carp and minnows during spring flooding. Swamps also provide good reproduction sites for herons and tree ducks.
A wet meadows can be recognized by their graminoid vegetation, i.e., plants like sedge that produce hard seeds. Over 150 plant species can be found in this habitat, including various species of Carex, reed canary grass and the common reed. The latter species is highly invasive and found everywhere in Québec. It is very aggressive and will prevent almost any other species from growing in the same location. It may even encroach on marshes, draining them and thus extending the characteristic conditions of wet meadows.
Wet meadows grow between swamps and marshes. Water is 30 cm deep during spring flooding but usually recedes completely in the summer. The ground is permanently saturated with water, which prevents trees and shrubs from growing.
The roots of plants growing in a wet meadow trap sediment brought by runoff, contributing significantly to water purification. The sediment deposits contribute to the development and reproduction of numerous invertebrates, which are in turn eaten by many species of fish, amphibians and birds. Wet meadows also provide good nesting sites for dabbling ducks and spawning grounds for several species of fish.
A marsh is characterized by soil permanently covered with water and by emergent plant species. An emergent plant has a stem that extends above water and roots below water level. Cattails, arrowheads and irises are examples of emergent plants.
Marshes provide food and shelter for many animal species. They are home to a large quantity of invertebrates and juvenile fish. Several species of waterfowl benefit from the abundant food to raise their offspring and to rest during migration. Many amphibians and reptiles live and reproduce in this habitat while muskrats and beaver build their lodges in marshes. In short, this habitat is among several that are essential to the survival of a wide range of species.
Aquatic vegetation bed
A aquatic vegetation bed is characterized by the abundance of submerged plants or plants with floating leaves. Common submerged plants include the Canada waterweed, watermilfoil and pondweed. Typical plants with floating leaves are duckweed and species of water lilies.
An aquatic bed is permanently flooded. In summer, the water can be as shallow as one metre, but during spring flooding it may be two or three metres deep.
Aquatic beds are very important places for fish to spawn, feed and find shelter. For many fish species, aquatic beds are similar to nurseries. They are also important for waterfowl during the fall migration when the water is shallow enough for them to feed efficiently and rest.
Much of the inhabited shores of Québec have been altered and developed, meaning that the natural buffer zone (including forests, swamps, marshes and other wetlands) has been destroyed or extensively altered to make way for roads, parking lots, residential areas, etc. This is especially true for the St. Lawrence River where at least 60% of the shoreline has been altered by humans. However, the level of urbanization varies. Some regions, such as Lac Saint-Pierre and small islands in the St. Lawrence, are much less altered, while others, particularly in the Montréal area, are up to 90% urbanized.The presence of a riparian buffer zone prevents erosion since plant roots keep the soil and sediment in place. Once riparian vegetation is removed, people frequently install structures that prevent erosion, such as concrete walls or rock embankments. It is important to realize that the best way to prevent erosion is to replant the vegetation cut down. This solution is less costly, doesn’t require repair over time, and provides suitable habitat for fauna and flora.
To learn more…
St. Lawrence Valley Wetlands
This site provides a web application that allows anyone to visualize the evolution of wetlands in the St. Lawrence Valley over time. Queries can be made for different geographic and time scales
Monitoring Wetland Vegetation
This website presents an Environment Canada project that has been using remote sensing and field observations to monitor wetland vegetation of the St. Lawrence River since the late 1970s.
Ducks Unlimited Canada
The mission of Duck Unlimited Canada is to conserve, restore and manage wetlands and associated habitats for North America’s waterfowl. These habitats also benefit other wildlife and people. The resource section offers portraits of wetlands in different regions of Québec. It also contains ample information about the role and function of wetlands.
Riparian buffer zone (in French)
This website is dedicated exclusively to the conservation and restoration of shorelines in recreational areas. Its mission is to help private shoreline owners apply best practices when they develop their shoreline or to help them to convert it to its natural state.
Schema wetlands : Environnement Canada
swamp : Alexandre Venne, Réserve de faune du lac Saint-François
wet meadow : Comité ZIP Ville-Marie
marsh : Comité ZIP Ville-Marie
aquatic vegetation bed and muskrat : Benoît Cloutier, Québec couleur nature 2006
urban shorelines : Comité ZIP Ville-Marie