The coverup: Using a simple, low-cost and low-effort solution to battle invasive species

If you’ve walked through Serpentine Wildlife Management Area in Surrey, or along the dikes at Addington Point in Coquitlam in recent years, you may have noticed something seemingly out of place: large stretches of black sheeting laid carefully across the ground. 

At first glance, they can look peculiar in wetlands known for their birds, plants and water features, but that simple sheeting is one of the most effective tools conservationists have for helping wetlands battle certain invasive species. 

Why can’t we leave invasive species alone? 

Wetlands are among the most productive and biodiverse ecosystems in Canada. They filter water, reduce flooding, store carbon and provide critical habitat for many birds, fish and wildlife species. But wetlands are highly vulnerable to invasive plants, which can spread quickly, overwhelming native species.  

Two challenging species in the Lower Mainland are yellow flag iris and Himalayan blackberry. 

Yellow flag iris, originally introduced as an ornamental plant with its vibrant yellow blooms, thrives in wet conditions. It forms dense mats that crowd out native wetland plants, alter water flow and reduce habitat quality for fish and wildlife. Himalayan blackberry, while more familiar and even beloved by some, can smother native vegetation and make wetlands less diverse and less resilient. Where these plants are introduced, they usually win in a battle for space. 

Left unmanaged, invasive species can fundamentally change the biodiversity of a landscape, driving out other plants, and along with them, the species who depend on them for habitat or food. 

A simple tool with powerful results 

To address this challenge, organizations like Ducks Unlimited Canada (DUC) have been using benthic barriers as one option in their invasive species tool kit in multi-year management efforts at several locations in B.C.’s Lower Mainland.  

Benthic barriers are heavy, reusable, opaque rubber-based sheets laid directly over the stalks of invasive plants. By blocking sunlight, reducing the plants’ access to oxygen and limiting physical growth, the barriers significantly reduce the survival opportunities for the invasive vegetation underneath. After one to two years, the sheeting is removed and reused elsewhere, and treated areas are replanted with native species. 

Each year, an area roughly the size of one to two tennis courts is treated at each site, while sites previously covered are replanted. 

A blank slate to restart from 

Once the barriers are removed, field crews plant native species such as salmonberry and other wet environment-adapted plants. These native plants help stabilize soils, improve habitat structure and resist future invasions, while also supporting the diets and habitats of local and migratory wildlife. 

The results are easily visible. Areas previously dominated by invasive plants now support healthy native vegetation, and planted species are thriving. What was once crowded and simplified becomes diverse again. 

Why this work matters now 

Invasive species are one of the leading threats to biodiversity worldwide. Managing them is rarely exciting, and it often takes patience, persistence and long-term investment, but it is essential. 

The work at these sites is made possible through funding from The Nature Force and TD Friends of the Environment Foundation. The work is carried out through the South Coast Conservation Land Management Program, a collaborative initiative involving provincial and federal governments, and conservation organizations like Ducks Unlimited Canada and The Nature Trust of BC.

“This kind of work doesn’t happen overnight,” Martin says. “But when you return to a site year after year and see native plants coming back, wildlife using the area again and the wetland functioning the way it should, it is rewarding.” 

A quiet success story 

Benthic barriers may not look impressive, but they represent a proven, low-cost, science-based approach to stewardship that gives wetlands the time and space they need to heal. 

So, the next time you see black sheeting stretched across part of a wetland, you’ll know that although it may look odd, it’s actually conservation in action.