Assessing the ecological influences on the efficacy of benthic barriers to control yellow flag iris in high priority waterfowl habitats across British Columbia, 2015-16

Final Report: Assessing the ecological influences on the efficacy of benthic barriers to control yellow flag iris in high priority waterfowl habitats across British Columbia, 2015-16

Goals and Objectives

Yellow flag iris is one of the Province’s problematic aquatic invasive species; occurring in shallow water along the riparian edges of streams, marshes and lakes. Once established, yellow flag iris is known to alter the hydrology, ecosystem complexity and functioning of an area, thereby reducing habitat suitability for native animal species. Invaded marshes in some eastern states are experiencing a significant displacement of native sedges and rushes with monocultures of yellow flag iris. Many over-wintering waterfowl species are dependent on sedge and rush seeds as a high-energy food source. Replacement of this food source with yellow flag iris would reduce the carrying capacity of these marshes to sustain waterfowl populations (ODA, 2013).

Additionally, breeding female dabbling ducks get most of the protein and calcium they need for egg laying from the consumption of aquatic macroinvertebrates living in shallow wetlands in their breeding grounds (Krapu and Reinecke 1992). Invertebrates are also consumed by a wide range of non-duck waterbirds such as cranes, grebes, herons, and shorebirds (Laubhan and Roelle 2001), and therefore are critical components of a healthy wetland habitat. Although undocumented, yellow flag iris may indirectly alter the macroinvertebrate community of an infested area through an alteration of the substrate. Thereby, potentially further reducing wildlife habitat.

Once established, yellow flag iris invades new areas via seed; having a high fitness rate, modeled to be 24% (ie– 24% of seeds from a parent plant will survive to form a new flowering plant). The high fitness rates are partially due to the buoyant nature of the seed, which can float for up to 7 months, in search of suitable substrate (Coops, 1990). However, due to the sensitive nature of aquatic ecosystems the use of herbicides is restricted. The most common practice prescribed for effective removal of small infestations of yellow flag iris is hand removal of emergent organs and rhizomes. Because hand removal of yellow flag iris is very labour intensive and difficult, thus larger populations are often left untreated.

Fortunately, yellow flag iris does appear to have an “Achilles heel”. Unlike other anoxic tolerant rhizomatous species, such as common club rush (Steinmann and Brandle, 1981) yellow flag iris continues to utilize stored carbohydrates rather than going dormant when no oxygen is present (Hanhijarvi and Fagerstedt, 1994). The result, under laboratory conditions, is death of rhizomes after approximately 35 days (5 weeks) in anoxic conditions (Hanhijarvi and Fagerstedt, 1994). By understanding the biology of the invasive species yellow flag iris, they can target the species weakest point (the non- dormant rhizomes) to remove the species from high priority waterfowl habitats.

Results from their first study (WHC #15-44) indicated that there is an environmental impact on the rate at which benthic barriers reduce cellular health. The benefit of benthic barriers is the short time required to impact cellular health. This short time may also translate into a reduced effect on the benthic community. In order to use benthic barriers in the most effective manner in terms of yellow flag iris control and limited benthic impact, they must first understand the time required to reach cellular death given different environmental parameters.

They propose to use rubber benthic barriers for approximately 133 days to test their ability to kill the rhizomatous network through the creation of anoxic and dark conditions at 7 sites across British Columbia.

Research question(s):

  1. How do environmental variables affect the rate of cellular death in yellow flag iris rhizomes underneath the benthic barriers?
  2. How many days are required to reach rhizome mortality at each of the sites?
  3. What is the effect of yellow flag iris infestations on macroinvertebrate communities?

Specific Habitat Products/Results Supported by WHC’s Contributions

They will produce a guide (“Land manager’s manual for installing benthic barriers”) for implementing benthic barrier treatments across the province, to be distributed to land management agencies. They envision a prescriptive manual for land managers (“Land Manager’s Manual for Installing Benthic Barriers”) on how to install benthic barriers, how to incorporate environmental parameters into expected outcomes, and a resource guide to purchase/acquire materials and supplies.

Benefits to Waterfowl, Wetland-Associated Species, and/or Other Wildlife

This project will contribute to the restoration and enhancement of bird species across the province through the enhancement of their critical habitat. This project will provide a tool for land managers to control yellow flag across an array of diverse habitat types. Aggressive control options are desperately needed as none currently exist for this species. Because their project spans the range of yellow flag iris distribution within British Columbia it does not directly fall within a priority area or link to a specific species but rather ties directly to restoration and enhancement of wetland productivity across a wide range of habitat types.

Relevance to Habitat Planning, Decision Making and/or Management

The project directly influences habitat conservation by improving wetland function for wildlife. Specifically, the removal of yellow flag iris improves waterfowl habitat through improved nesting and breeding opportunities. Yellow flag iris also affects water quality by trapping sediments and narrowing stream channels, thus affecting the hydrology of an ecosystem.

Private landowners, municipal, regional districts, Provincial, not for profit and Federal level agencies will all benefit from being able to control yellow flag iris on their land. Regardless of what the land is managed for (waterfowl, scenic, fish habitat, hydrology etc.) invasive species affect proper ecosystem functioning.

Project Location

  1. Member(s) of Parliament representing the project area(s): Somenos = Jean Crowder, Buttertubs= James Lunney, Cheam = Mark Strahl, Little White Lake = Colin Mayes, Creston Valley =David Wilks, Mel Deanna = David Wilks, Lac La Hache = Cathy McLeod
  2. Province: British Columbia
  3. Municipality / county / town / city: Somenos = Duncan, Buttertubs = Nanaimo, Cheam =Chilliwack, Little White Lake = Salmon Arm, Creston Valley = Creston, Mel Deanna =Castlegar, Lac La Hache = Williams Lake
  4. Area (acres) of wetlands in research area: See descriptions for each site under Project Description
  5. Area (acres) of uplands in research area: None – all of the research areas are riparian

Project Contact

For more information on this project, please contact Dr. Catherine Tarasoff, Adjunct Professor, Thompson Rivers University, Kamloops, BC.