Monitoring and Mitigating Reed Canary Grass in Stanley Park, BC

Reed canary grass (Phalaris arundinacea), abbreviated RCG, is an invasive species that threatens native flora and fauna via competition and alterations to the abiotic environment. In the past few years, this invasive plant has rapidly spread throughout parks in Vancouver, BC, including Stanley Park, which is bordered by downtown, English Bay and the Burrard Inlet. The Stanley Park Ecology Society (SPES) strives to uphold the ecological integrity and biodiversity of Stanley Park; thus, being able to monitor and manage the spread of RCG properly is of high interest and priority. Our team will assist in their mission by providing the following deliverables in this report: 1) an up-to-date map of RCG abundance and distribution in the park, 2) a map showing areas where RCG growth and invasion is most susceptible based on abiotic, environmental factors, and 3) an RCG management plan including recommendations. These deliverables will help SPES locate areas of high priority for active management, understand where invasions are most likely to occur, and decide which management and/or monitoring techniques would work best for each area. The objectives satisfied by our project will gear invasive management practices in the park towards a customized plan that will increase the effectiveness of restoration approaches and ultimately improve the parks’ biodiversity. The invaded areas are categorized as low, medium, or high density, which was determined by their current abundance and distribution within Stanley Park from 2019-2021. Distribution data was collected by TREK students, SPES volunteers, and members of our team. Reed canary grass was found to persist in high densities near fresh-water bodies and trails and in lower densities further away from water bodies. This shows that the presence of fresh water has a large impact on the density of RCG. Susceptible areas were determined by predicting future behaviours of the species, based on abiotic factors such as sunlight availability, proximity to potential carriers, and hydrology. The data used to model the susceptibility included distance from water bodies, distance from trails, and LiDAR canopy cover. Highly susceptible areas were found in similar locations as high density areas, however not always near trails, possibly as areas away from trails were not fully surveyed in the field. RCG is most likely to continue spreading along the shorelines of Beaver Lake and Lost Lagoon (two large watersheds within Stanley Parkillustrated in light blue in Figure 2 under ‘Results’), as well as to forested areas with large breaks in the canopy. The growth patterns of RCG based on our research indicate that water and sun availability are most influential when considering the spread of the invasive species. We identified 22 reports and management plans published by global institutes and existing literature. Then we analyzed the materials by conducting a simple qualitative analysis. These methods provided us with the baseline to create specific management techniques for different sizes and RCG densities of patches which were outlined (Figure 4), with mowing recommended for larger areas and a combination of hand-pulling, mulching, and shading recommended for smaller areas. Aquatically-approved herbicide would also be a very effective control method, however this needs to be approved by the Vancouver Park Board. These objectives aim to decrease the spread of Reed canary grass within Stanley Park and increase the park’s biodiversity, following the consideration and implementation of the management plan by the Stanley Park Ecology Society.

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