Horsetail spike-rush (Eleocharis equisetoides) recovery strategy: chapter 3

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Recovery

2.1    Rationale for Recovery Feasibility

The recovery of horsetail spike-rush is technically and biologically feasible. The only historically documented population in Canada still exists. Although survey data are insufficient to identify a population trend or recruitment rate, successive recent visits suggest that the number of culms and area of occupancy remain stable. There are individuals within the species’ North American range that are capable of reproduction. However, the feasibility of reintroduction is not known. The current habitat may be assumed to be sufficient for the species’ requirements, since it was first recorded here in 1953, and no other supporting populations are known from southwestern Ontario, in spite of intensive botanical exploration. There are only a few recognized threats to the species, and most of these can be monitored with a view to taking proactive measures should imminent threats to the viability of the extant population become apparent. Active recovery techniques are not currently regarded as necessary, because the known habitat and estimated population of horsetail spike-rush are not believed to be in decline.

It should be recognized that horsetail spike-rush is naturally very rare in Canada, and it is not known whether its current population or supporting natural processes are sufficient for it to persist over the long term. However, available evidence suggests that a goal of maintaining its single natural occurrence is likely attainable.

2.2    Recovery Goal

The long-term recovery goal is to maintain the single known occurrence of horsetail spike-rush at or near its recorded areal extent of 5–10 m².

2.3    Recovery Objectives (next five years)

1.     Annually monitor the number of culms and suspected threats (Phragmites spread, water levels, herbivory) in order to assess trends and severity of threats over five years.

2.     Investigate common reed removal methods, and, if necessary, control or remove common reedin an adaptive management framework.

3.     Investigate seed viability and archiving techniques, and, if considered feasible, collect and preserve horsetail spike-rush seeds. Investigate the feasibility of rhizome harvesting, and implement as appropriate.

4.     Complete critical habitat mapping, and ensure its protection.

5.     Investigate and verify any reported new locations of horsetail spike-rush in Canada.

6.     Determine the tolerance of horsetail spike-rush to water level fluctuation, the minimum viable population and viability of the extant site, and the extent to which loss of genetic diversity poses a threat to the species.

2.4    Rationale for Goals and Objectives 

The recovery goals and objectives reflect the fact that the sole occurrence is protected through federal legislation, and natural processes within the national wildlife area are largely intact.

Horsetail spike-rush is naturally rare in Canada, likely remaining here as a relict Atlantic coastal plain species at the close of the last glaciation (Reznicek 1994; Jackson and Singer 1997). There is no evidence to suggest that any other occurrence of this species has been extirpated from Canada within European history. This population has been known from this site for several decades; assuming that conditions remain the same, it is reasonable to assume that it will persist here. Attempting to increase the area of occupancy, number of locations, or population abundance is therefore not recommended. Similarly, aiming to “delist” horsetail spike-rush as a species at risk is unrealistic, as it has probably been extremely rare in Canada since pre-European times. Given the very restricted occurrence of this species, archiving seeds or propagation from rootstock would protect the population against extirpation in the event of a severe and unforeseen impact.

Managing Phragmites spread near this site is recommended in spite of uncertainty as to whether Phragmites represents a threat. This is because controlling Phragmites while abundance is low is more likely to be effective.

2.5    Approaches Recommended to Meet Recovery Objectives

Strategies intended to reduce or eliminate threats are listed in Table 2. Strategies include monitoring, inventory, habitat management, habitat mapping, and research. They are focused on identifying, refining, and managing threats.

2.6    Critical Habitat

2.6.1   Identification of the species’ critical habitat

The critical habitat for horsetail spike-rush is being identified, to the extent possible, in the recovery strategy. Further identification and refinement of the critical habitat will take place following the completion of the schedule of studies and will be included in the action plan. Critical habitat includes the known area of occupancy and the marsh community on Long Point in which it occurs. The buttonbush – red osier dogwood wetland community where horsetail spike-rush occurs should be described and mapped to the level of ecosite type following the Ecological Land Classification for Southern Ontario (Lee et al. 1998), which is a standard protocol for vegetation community mapping in Ontario. However, critical habitat will be limited to the pond complex that the species inhabits and will not extend to adjacent wetland areas unless new occurrences of horsetail spike-rush are discovered.

The minimum area of critical habitat required to maintain a viable population of horsetail spike-rush is not known, since there is no information on what number of individuals represents a viable population or its specific requirements. Given its historically low abundance in Canada in spite of the apparent presence of similar habitat, the extent of this vegetation community is unlikely to be limiting the population’s long-term viability. Since the recovery goal is to maintain the occurrence at or near its recorded extent (see above), it will be assumed in the absence of other evidence that the natural habitat it currently occupies will be sufficient to maintain it at these levels.

Critical habitat for horsetail spike-rush includes the inland pond where it grows in sandy organic muck along the south-facing shoreline. The pond lies between two stabilized dune ridges near the tip of Long Point National Wildlife Area. Horsetail spike-rush is considered an aquatic species, growing in water between 4 and 35 cm deep. The shoreline community at this location is dominated by buttonbush and red-osier dogwood. Other species observed growing in association with horsetail spike-rush include water bulrush, Small’s spike-rush, grass-leaved pondweed, long-leaved pondweed, common coontail, slender naiad, bulhead pond-lily, northern wild rice, and slender sedge.

2.6.2   Examples of activities likely to result in destruction of critical habitat

There are no demonstrated human activities that are likely to destroy critical habitat at this single location. All possible threats at this site are the result of natural processes.

2.6.3   Schedule of studies to identify critical habitat

To further refine the critical habitat definition, the studies described in Table 3 should be completed.

However, since critical habitat is protected from threats to its survival due to its location within a National Wildlife Area intensive demographic studies are not urgent. No specific timelines are therefore suggested for these research questions.

2.7    Existing and Recommended Approaches to Habitat Protection

All critical habitat for horsetail spike-rush known in Canada is in a national wildlife area. Ninety days after the final version of this strategy is included in the public registry, a description of the critical habitat will be published in the Canada Gazette. The prohibitions under SARA (Section 58) will then apply after a period of 90 days following the description in the Canada Gazette. This will complement existing protection in Long Point National Wildlife Area (McKeating 1983) under the Canada Wildlife Act. No land acquisition or policy approaches are required unless new sites are discovered. Protecting habitat at this site is related only to managing threats if required.

If the species is discovered on private or provincial lands, the Ontario Ministry of Natural Resources will be engaged in updating the recovery strategy.

2.8    Performance Measures

Recovery can be considered successful in 2011 if the following have been met:

·       Objective 1 -- Annual monitoring data show that the areal extent, number of culms, and number of fruiting culms (or other indicators, as outlined in a monitoring method) have remained stable or increased.

·       Objective 1 -- Monitoring has determined whether herbivory or changes in water level appear to be affecting the number of culms (i.e., threats have been confirmed), and, if this is the case, possible actions have been investigated and implemented as appropriate.

·       Objective 2 -- Stands of common reed and other invasive aquatic plants are absent from the pond or at least have not expanded from 2005 levels and do not pose an immediate threat to the habitat of horsetail spike-rush.

·       Objective 3 -- Long-term seed storage and viability and/or rhizome propagation have been investigated and, if feasible, undertaken.

·       Objective 4 -- Critical habitat has been mapped at all extant locations within a year after discovery for new locations and by 2007 for Long Point National Wildlife Area.

·       Objective 4 -- Protection of horsetail spike-rush has been incorporated into any new management plans or other relevant documents for Long Point National Wildlife Area, and area managers remain involved with recovery decisions and activities.

·       Objective 5 -- New reports of horsetail spike-rush at other Canadian locations have been investigated and, if present, incorporated into recovery efforts.

·       Objective 6 -- Research activities carried out and research results have been considered to improve management activities.

2.9    Effects on Other Species

Negative impacts on other native species are not anticipated through the completion of the proposed recovery activities, which focus mainly on retaining natural ecological function of the immediate area and monitoring the population of horsetail spike-rush.

However, this strategy recommends the control of common reed; depending upon the methods used, this may have implications for other native plant or animal species living on or near these stands. Investigating non-chemical or biological control methods may help to reduce this potential impact. Although the herbicide Rodeo^® is used widely in U.S. Atlantic coastal marshes for the control of Phragmites (Marks et al. 1993; Mal and Narine 2004), it is not currently licensed for use in Canada.

No other species at risk are known to co-exist with horsetail spike-rush, so the activities recommended in the strategy are unlikely to have any effect on other species at risk.

2.10  Recommended Approach for Recovery Implementation

A single-species approach to recovery is being proposed because of the limited distribution of horsetail spike-rush and because no other species at risk co-exist with it. Integrating these goals, objectives, and actions into vegetation or ecosystem management plans for Long Point National Wildlife Area is recommended.

2.11  Statement of When One or More Action Plans in Relation to the Recovery Strategy Will Be Completed

An action plan will be completed for horsetail spike-rush by 2008.