Invasive Species Management in Hillman Marsh Shorebird Cell

The Essex Region Conservation Authority has recently undertaken targeted control of Flowering rush within the managed shorebird habitat cell at Hillman Marsh Conservation Area. Flowering rush is a restricted invasive aquatic plant in Ontario that can form dense stands, displace native vegetation, reduce biodiversity and alter wildlife habitat, including bird nesting and rearing areas. Early control is important in preventing this invasive species from spreading further into the larger wetland system. The goal is to address Flowering rush before it becomes as difficult to manage as other invasive plants such as phragmites.

The treatment was completed within the constructed shorebird cell while it was in a dry, managed condition and completely contained, with no surface water present. The shorebird cell is a constructed and actively managed habitat that is drained annually and later managed through flooding and drawdown to create shallow-water and exposed mudflat habitat for migrating shorebirds.

Herbicide treatment is never undertaken lightly. However, it is currently one of the only effective tools available to control Flowering rush at this stage. Imazapyr, the active ingredient used in the treatment, is also the active ingredient in a Canadian herbicide specifically registered for the control of Flowering rush. Available environmental assessments indicate that imazapyr has low direct toxicity to aquatic invertebrates and other wildlife when used according to approved conditions.

In this contained shorebird cell, targeted treatment helps reduce the risk of this invasive species spreading into the broader marsh system, where it could cause much greater long-term ecological harm. Dense stands of Flowering rush can also reduce the open mudflat and shallow-water conditions that the shorebird cell is specifically managed to provide. The cell is periodically drained and has also been planted with agricultural crops as part of its ongoing management.

Hillman Marsh is a significant migration stopover, and ERCA is committed to managing invasive species responsibly to protect the long-term ecological health of this unique habitat.