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Recovery Strategy for the False Hop Sedge (Carex lupuliformis) in Canada [Proposed]

4. Threats

4.1 Threat Assessment

Table 1. Threat Assessment Table.

ThreatLevel of Concern1ExtentPopulationFrequencySeverity2Causal Certainty3
Habitat loss or degradation
Alteration of water regimeHighWidespreadCurrentContinuousHigh/
Moderate4
High
Recreational and landowner activitiesMediumWidespreadCurrentContinuousModerateMedium
Residential developmentLowLocalizedHistoricalContinuousHigh/
Moderate
High
Changes in ecological dynamics or natural processes
Closure of vegetationHighLocalizedCurrentContinuousHigh/
Moderate
High
Alien, invasive or introduced species/genome
Invasive alien plant speciesMediumWidespreadCurrentContinuousUnknownHigh
ParasitesLowWidespreadCurrentContinuousUnknownLow
Pollution
Garbage depositionLowLocalizedCurrentContinuousLowLow

1 Level of Concern: signifies that managing the threat is of high, medium or low concern for the recovery of the species, consistent with the population and distribution objectives. This criterion considers the assessment of all the information in the table. Threats with a low Level of Concern are listed and described but may not be specifically addressed in the recovery approaches.
2 Severity: reflects the population-level effect (High: very large population-level effect, Moderate, Low, Unknown).
3 Causal Certainty: reflects the degree of evidence that is known for the threat (High: available evidence strongly links the threat to stresses on population viability; Medium: there is a correlation between the threat and population viability, e.g. expert opinion; Low: the threat is assumed or plausible).
4 Each threat assessment criterion is assessed for each population and for the entire range. When two qualifiers are indicated in a box, it means the identified threat does not have the same impact at both levels (scale of populations/entire range).

4.2 Description of Threats

The threats listed below are presented in decreasing order of the level of concern. It should also be noted, however, that a limited number of extant populations (14) with low abundance (<400 individuals total) distributed within a restricted geographic region poses a significant challenge for the long-term persistence of the False Hop Sedge.

Alteration of the water regime

Natural fluctuations in water levels as well as drought periods appear to play a crucial role in the establishment and maintenance of False Hop Sedge and its habitat. Indeed, episodic high-water levels can provide suitable habitat by removing competing plant species and by eroding more forested riparian habitats thereby creating openings that are suitable for the establishment of new individuals (Labrecque, 1998; Bachand-Lavallée and Pellerin, 2006; Jolicoeur and Couillard, 2006; COSEWIC, 2011).  However, excessive water saturation of the substrate does not favour the expansion of Silver Maple swamps (Jean Morin, personal communication) and appears to impede the emergence of seeds and reduce the vigour of individuals (Letendre et al., 2007). Indeed, it has been shown that high water levels such as those observed on the Richelieu River since the 2000s (and particularly during the spring 2011 floods), cause the loss of False Hop Sedge plants (Letendre et al., 2007; Stephanie Pellerin, personal communication). Locations where the suitable habitat consists solely of a narrow strip of vegetation hemmed in along the river by private residences (e.g., Sainte-Anne-de-Sabrevois, McGillivray Bay) are more at risk from this threat.

Dam construction can exacerbate the negative effects of high water levels. In Quebec, construction of the Carillon Dam in the 1950s altered the hydrological regime of the Ottawa River, leading to shoreline erosion in areas upstream of the dam which may have caused the extirpation of the populations in the Lac des Deux-Montagnes region (Jolicoeur and Couillard, 2006). The threat of dam construction remains along the Richelieu River in Quebec but is unlikely in Ontario since most populations are found in vernal pools.

In several Ontario populations, surface or subsurface drains (agricultural and/or municipal) are situated right next to most extant populations and appear to have dried the soils at the West Lorne and London locations. In Quebec, the location of extant populations within 10-15 m of large watercourses suggests that drainage is not a threat. However, some extirpated populations where reintroductions are being considered are more vulnerable as they are further away from these watercourses. Changes in the hydrological conditions of the habitat can promote the growth of competing plant species in the shrub and herb layers, which can be detrimental to False Hop Sedge. The decline observed in several populations in Ontario and Quebec appears to be related to this factor (COSEWIC, 2011).

Closure of vegetation

False Hop Sedge is a shade-intolerant species and as such, the vigour of individual plants appears to be positively correlated with the openness of the surrounding vegetation (Labrecque, 1998; Letendre et al., 2007). Furthermore, germination does not occur in habitats with a low light intensity (Schütz, 2000). Shading through vegetation succession therefore presents a threat to this species (COSEWIC, 2011). This appears to have been the cause of the extirpation of the Grande Baie d’Oka and Rigaud (Quebec) populations as well as the Amherstburg (Ontario) population (Labrecque, 1998). As found in many other species of Carex, the seeds may nonetheless remain viable in the soil for more than 10 years (Leck and Shutz, 2005) and germinate following disturbance of the soil or opening of the canopy. This situation was observed at the Mount Brydges (Ontario) population where forest harvesting created openings in the canopy, promoting a dramatic increase in the number of individuals at this location (from 25–30 in 1992 to 1075 in 2003). However, competition by herbaceous vegetation and closing of the canopy in subsequent years reduced the number of individuals to 29 in 2009.

Invasive alien plant species

Invasive alien plants can affect the survival of False Hop Sedge by competing with it for sunlight and nutrients as well as by acting as a barrier to seed dispersal (COSEWIC, 2011). The absence of water level fluctuations or low water levels is conducive to the establishment of invasive plants (Hudon et al., 2005). Species that may be more problematic are Purple Loosestrife (Lythrum salicaria), Reed Canary Grass, Reed Manna Grass (Glyceria maxima) and Common Buckthorn (Rhamnus cathartica). All the individuals at the Pointe du Gouvernement sector of the Henryville (Quebec) population appear to have disappeared due to the establishment of a dense stand of Reed Canary Grass (COSEWIC, 2011). European Water-chestnut (Trapa natans), although not currently present at False Hop Sedge populations, occur in some areas along a tributary of the Richelieu River (Quebec) as well as upstream of the Carillon dam on the Ottawa River on the Ontario side. This species forms a dense carpet on the water surface which could eventually invade False Hop Sedge populations and inhibit their growth and dispersal ability.

Recreational and landowner activities

A number of populations are located in areas where mortality through trampling of the plants may be a threat because of public access or landowner activities (e.g., grazing, hunting, clearing of underbrush and tree harvesting). All-terrain vehicle (ATV) use has been observed near two populations in Quebec (Carillon Island and Henryville (Labrecque, 1998)). Proximity of False Hop Sedge to residences or recreational areas also increases the risk of vandalism, as was observed in the Parc national d’Oka, where a number of transplanted tufts were pulled up by park users.

Parasites

False Hop Sedge and other members of this plant family are hosts of a dipteran[7] parasite. The larvae of this parasite develop inside the achenes, causing a deformity that affects the position of the fruit casing. This phenomenon affects all extant Canadian populations, but more so the one at Saint-Blaise-sur-Richelieu (COSEWIC, 2011). The effect this parasite has on the species is unknown (Labrecque, 1998). In addition, an alien aphid (Ceruraphis eriophori) has been observed on several plants in Quebec and may be present in Ontario. The presence of the aphids appears to be linked to premature drying of plants (Letendre et al., 2007) and appears to be correlated with the drying and mortality of a number of individuals transplanted in Quebec in 2006. It is possible the aphid could have a significant impact on the species’ long-term survival (COSEWIC, 2011). A sawfly (Pachynematus corniger) has also been observed feeding on the leaves of False Hop Sedge in Quebec. The impact of sawfly feeding on the survival of False Hop Sedge plants has not been studied, but it appears to reduce the plants’ vigour (COSEWIC, 2011).

Garbage deposition

Garbage or other waste/debris can impede the growth of False Hop Sedge. This has been observed around the population in London (Ontario) and the populations along the Richelieu River. In Quebec, debris consist of floating materials deposited along the shoreline by flood waters and waves (COSEWIC, 2011).

Residential development

Residential development affects populations through habitat loss and degradation. Nearly two thirds of the shoreline of the Richelieu River have been altered, mainly as a result of residential development and the construction of marinas. Shoreline development likely explains the extirpation of the Sainte-Anne-de-Sabrevois, Saint-Paul-de-l’Île-aux-Noix, Iberville and Saint-Blaise-sur-Richelieu populations (Labrecque, 1998). This threat is more limited now because of various legislative measures that protect wetlands. The COSEWIC status report (COSEWIC, 2011) mentions residential development near the London population; however, this does not appear to be a major threat at present because the city owns the site and is not likely to develop it.

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5. Population and Distribution Objective

The population and distribution objective is to maintain or, where biologically and technically feasible, increase the abundance and area of occupancy of the False Hop Sedge in Canada. At the present time, it is not possible to establish a quantifiable objective regarding the appropriate abundance of individual populations or the overall population in Canada but this may become possible once viability analyses are conducted.

In the southernmost part of Ontario and Quebec, a high rate of wetland loss was observed during the last century along with significant alteration of riparian habitats colonized by False Hop Sedge. This has resulted in the persistence of very few individuals within a limited number of populations, therefore increasing the vulnerability of the species to catastrophic events. For example, during the spring of 2011, a severe flooding took place along the Richelieu River wiping out all but two of the naturally-occurring individuals. Had reintroduction or transplantation efforts not been undertaken in previous years, the species would be nearly extirpated from the Province of Quebec today. At the same time, such events can generate suitable habitats that can be colonized by the species if sufficient seed-producing individuals survive. Extant sites may also bounce back from such events if the seedbanks are not flooded for an extended period.

The objective of the federal recovery strategy corresponds to those set out in the Government of Quebec’s conservation plan for the False Hop Sedge (Jolicoeur and Couillard, 2006) which are to : 1) protect and ensure the long-term maintenance of all extant populations; and 2) introduce or reintroduce the species, if feasible, in the physiographic units[8] where it has become extirpated. A similar conservation plan has not been prepared by the Province of Ontario.

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6. Broad Strategies and Approaches for Meeting Recovery Objectives

6.1 Actions Already Completed or Currently Underway

Conservation and stewardship

  • Seeds were sent to Agriculture and Agri-Food Canada’s seed bank in Saskatoon. More than 2500 achenes obtained from nearly all the populations in Canada (except Ailsa Craig and Lambeth in Ontario) were also sent to the Millenium Seed Bankof theRoyal Botanic Gardensin Kew (England) for long-term conservation. Seeds were collected in Quebec and Ontario and seedlings were grown to reintroduce individuals in certain populations.
  • Habitats have been restored and individuals were reintroduced in two extirpated populations in Quebec (Sainte-Anne-de-Sabrevois and Grande Baie d’Oka) and transplanted in two populations in Quebec (Saint-Blaise-sur-Richelieu and McGillivray Bay) and one population in Ontario (West Elgin). In 2010, the survival of transplanted individuals ranged from 17 to 82%, and the survival of seed-producing individuals ranged from 15 to 60% (COSEWIC, 2011).
  • A portion of the Marcel-Raymond Ecological reserve has been legally designated as a plant habitat[9] (Baie-des-Anglais) under the Quebec Act Respecting Threatened and Vulnerable Species.
  • In revising their regional development plan, the Haut-Richelieu, Deux-Montagnes and Argenteuil regional county municipalities designated False Hop Sedge habitats as ecologically significant areas. In these areas, only developments devoted to education, such as interpretive trails, can be authorized.
  • The projected Samuel-de-Champlain biodiversity reserve in Quebec (Natural Heritage Conservation Act; R.S.Q. c. C-61.01) was designated in 2011 to protect 487 ha of wetlands in the Richelieu River (Quebec) sector between Saint-Jean-sur-Richelieu and the United States border.
  • In Ontario, the habitat of the False Hop Sedge is protected under the Endangered Species Act, 2007.

Surveys and monitoring

  • Since 2005, the extant populations of Quebec have been surveyed and mapped every year or two and a management approach has been recommended for each (Jolicoeur and Couillard, 2006).
  • Nine new locations suitable for the reintroduction of the species have been identified along the Ottawa River (Bachand-Lavallée and Pellerin, 2006; Letendre et al., 2007).
  • In 2009, surveys were conducted at all the extant populations in Ontario as well as the extirpated Amherstburg site.

Outreach and communication

  • Outreach activities directed at the general public as well as owners of properties located near False Hop Sedge populations of the Richelieu River were carried out in 2006 and 2007 (Bachand-Lavallée and Pellerin, 2006; Letendre et al., 2007).

6.2 Strategic Direction for Recovery

Table 2. Recovery Planning Table.

Threat or LimitationBroad Strategy to RecoveryPriorityGeneral Description of Research and Management Approaches
All

 

Conservation of the species, its suitable habitat and the adjacent riparian zone

High
  • Apply legal and stewardship measures within the localities hosting populations and in the adjacent areas in order to reduce the impacts of the main threats.
  • Continue or implement management approaches to increase the abundance of the species and the area of suitable habitat, where feasible:
    • ex situ cultivation of the species using artificial propagation techniques;
    • restoration of habitats;
    • reintroductions in extirpated populations;
    • transplantations in extant populations.
Gaps in knowledge related to demographics and biology Survey and monitoringHigh
  • Develop and implement a standard inventory and monitoring protocol for collection of comparable data in Ontario and Quebec including:
    • Marking of all naturally-occurring individuals at extant populations as well as reintroduced or transplanted individuals in order to better monitor population dynamics and trends.
    • Gather georeferenced data on individual tufts as well as on the area of occupancy for the tufts, particularly in the Ontario populations.
  • Conduct an inventory of suitable habitat outside of known localities at regular intervals.
All; Gaps in knowledge related to demographics and biology ResearchHigh
  • Develop techniques to increase the vigour and persistence of transplants:
    •  Study the species’ capacities to adapt to ecological conditions (ex. availability of light, frequency and length of flooding events) at the northern edge of its distribution
  • Study the species’ population dynamics
    • Investigate the viability of seeds in the soil
    • Determine how seed dispersal influences population dynamics
    • Conduct a population viability analysis
  • Study genetic aspects that could limit our abilities to recover the species (ex. hybridization)
AllCommunication and outreachMedium
  • Develop and implementation of a communication strategy for partner agencies, interest groups, private landowners and the general public.

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Footnotes

7 Insects of the Order Diptera, also known as the true flies, characterized by a single pair of wings; includes houseflies, mosquitoes and gnats.

8 According to the Cadre écologique de référence of the Quebec Ministère du Développement durable, de l’Environnement et des Parcs (Li et al.1994), physiographic units correspond to landscapes elements measuring in the order of 1 000 km².

9 According to section 17 of the Act “No person may, in the habitat of a threatened or vulnerable plant species, carry on an activity that may alter the existing ecosystem, the present biological diversity or the physical or chemical components peculiar to that habitat."