Several times throughout this series, we have discussed our tendency to ignore and overlook periphery spaces: edges, corners, drainage ditches, highway medians, etc. Unfortunately, by doing so we risk allowing these spaces to become degraded, decreasing usable habitat and ecosystem services. Edge habitats where two environments intersect often create the most biodiverse areas. These forgotten spaces may not be as flashy or beautiful as other environments, but that does not mean they are any less ecologically important and changes to them can pose a serious threat to environmental stability.
Riparian zones are the transition area between aquatic and terrestrial ecosystems fostering unique ecological communities specifically equipped for these unique environments. Good riparian management is considered vital in maintaining the health of water bodies and provides several significant benefits to neighboring communities. Healthy, robust riparian zones reduce and filter runoff and protect aquatic environments from excessive sedimentation and erosion. They also buffer against the effects of storm surges and increases the absorption of flood water. Riparian zones are instrumental in water quality improvement, by lowering nitrate contamination in surface runoff, such as manure and other fertilizers from agricultural fields, that would otherwise damage ecosystems and human health.
Despite their ecological significance, there is little awareness of the importance of riparian zones among the broader public. Instead, riparian zones which to some look like dense, weedy thickets, can be seen as obstacles to human recreation and are frequently removed to make way for a better view of the water, lawns, parks, walking paths, and other projects. Sometimes, especially after property owners begin to experience the effects of having removed the riparian zone mentioned above, they are replaced by rock walls and other engineered (hard or grey) alternatives. These solutions are very costly and often divert problems downstream. However, complex root systems in natural, vegetated riparian zones hold the soil together and prevent erosion. Without these checks in place, constant weathering from moving water, rainfall, wind, storm surges, and even boat wakes make water banks susceptible to being undercut and eroded. This can have serious implications for wildlife as well as neighboring human communities by decreasing property values, land loss, and increased runoff which can lead to such issues as cyanobacteria (blue green algae) blooms, among others.
The PWA has long stressed the importance of proper riparian management which includes maintaining vegetative cover, minimizing compaction from human/ animal movement and vehicle traffic, avoiding fertilizers and other chemicals near riparian zones, and more. While being precautionary and conserving natural riparian zones is the most effective way of protecting these ecosystems, several remediation strategies also exist.
In the 2022 field season, the PWA used an alder-weaving bank stabilization technique in an attempt to reverse erosion in both the Haut-du-Ruisseau Nature Park and Centennial Park. Alder weaving involves weaving young, flexible alder trees between stakes embedded around the riverbank while interweaving evergreen boughs. Over time, the woven boughs should trap and build sediment around the structure. The alders that take root will also begin to stabilize this newly infilled area. For more information, see this video on alder weaving.
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