Recovery Strategy for the Common Hoptree in Canada [Final] 2012: Critical Habitat

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Critical habitat is defined in section 2(1) of SARA (2002) as “the habitat that is necessary for the survival or recovery of a listed wildlife species and that is identified as the species' critical habitat in the recovery strategy or in an action plan for the species”. In order to achieve the population and distribution objectives, this recovery strategy identifies critical habitat for the Common Hoptree across its range in Canada, to the extent possible at this time.

The locations and attributes of critical habitat were identified using the best available information, including observation data, indicating the presence of a single tree or a cluster of trees. In other circumstances, while specific point locations were not available, the species had been documented as occurring within a particular vegetation type(s) on a specific property. These data were collected by regional, provincial and federal agencies and their contractors, as well as by non- government organizations and individuals over the course of many years. Locations of known Common Hoptrees were obtained from Jalava et al. (2008), Dobbyn (2005), Natural Heritage Information Centre (NHIC unpub. data), Nature Conservancy of Canada (unpub. data), OMNR (unpub. data), and Ontario Nature (unpub. data). Additional map components were provided by the North American Atlas (Figures 4-35), OMNR's Land Information Ontario (Figures 4-14 and 16-35), Parks Canada Agency (Figure 5-8, 13-15, and 35), Nature Conservancy of Canada (Figures 5-7), Dougan and Associates (2007 – Figure 8), Essex Region Conservation Authority (2010 – Figures 6, 14, and 15), OMNR (Figure 12), Ontario Nature (Figure 6), and Ontario Parks (Figure 9).

Across the species' range, the biophysical attributes of Common Hoptree critical habitat include open to moderately vegetated areas, often with a relatively high level of natural disturbance or harsh environmental conditions. These attributes occur in the following locations and situations:

Figure 3: Conceptual illustration of critical habitat (9 m radius tree root zone) around a single Common Hoptree.

General locations of Common Hoptree critical habitat are shown in Figure 4. Site-specific critical habitat maps for 43 critical habitat parcels, covering 22 of 35 extant populations and six of seven core areas, are provided in Appendix B.

Figure 4: General locations of critical habitat for Common Hoptree in Canada.

Ecological Land Classification Vegetation Type Mapping

A number of approaches were used to identify critical habitat for the Common Hoptree across its Canadian range based on the type and availability of information. Where data were available to identify a Common Hoptree or trees within one or more ELC units (vegetation type or ecosite, where vegetation types were not available), critical habitat was identified as the boundaries of the occupied ELC unit(s), provided that they were considered suitable for survival and recovery of the species, as follows:

Critical habitat has been mapped in all but the latter two locations where the area within which critical habitat is found has been mapped. This is due to the fact that the location of all Common Hoptrees at these two sites is not currently known.

Other Types of Habitat Mapping

When ELC data were not available, other types of vegetation mapping were used to identify Common Hoptree critical habitat, as follows:

Bounding Area

Where no vegetation community mapping was available, an occupancy approach, based on the observation of trees, was applied. Critical habitat was based on UTM (Universal Transverse Mercator coordinate system) locations of individual trees or clusters of trees, obtained using a GPS (geographic positioning system) unit. Coordinates obtained using this technology are expected to be accurate to at least 10 m.

In these situations, the area within which critical habitat (based on biophysical attributes) is found is identified as a rectangle that stretches 150 m perpendicular to the water's edge to encompass the tree(s) and extends along and parallel to the shoreline 150 m on either side of the Common Hoptree(s). The 150 m value was chosen as surveyors in the Niagara Region indicated that most populations seemed to be a maximum of 150 m long (Brant pers. comm. 2009). As some data points represent multiple trees and it is unclear where within the tree cluster the coordinates were taken, the 150 m distance has been applied in either direction parallel to the shoreline to ensure critical habitat protection along a 300 m stretch of shoreline. This approach was applied in the following locations:

Pelee Island
Essex County (NHIC unpub. data):
Elgin County (Dobbyn pers. comm. 2011)
Regional Municipality of Niagara (OMNR unpub. data):

Where trees were found more than 150 m away from the shoreline, the area within which critical habitat is found is identified as a circle with a radius of 150 m from the trunk of each live, individual, naturally occurring Common Hoptree or a data point representing multiple individuals. This approach was applied in the following locations:

Regional Municipality of Niagara (OMNR unpub. data):

Documentation, prior to severe degradation of all Middle Island vegetation layers (ground
cover to canopy) by hyperabundant, nesting Double-crested Cormorants, indicates that Common Hoptrees were found along the shoreline, as would be expected of a species that does not flower or germinate in partial to full shade (Rennie 1982, Kamstra et al. 1995, Ambrose 2002). Efforts are underway to protect and restore the ecological integrity of the Carolinian ecosystem on Middle Island. Specific aims include significantly reducing the loss of dense (healthy) forest canopy cover on the island due to the impacts of Double-crested Cormorant nesting and protecting SARA-listed species at risk (Dobbie 2008). Given that this goal, linked to historic conditions on the island, is expected, as a result of light availability, to once again limit reproductive and germinating Common Hoptrees to the vegetation/shoreline interface, critical habitat is identified as follows:

Existing trees growing outside of this area may persist, but are not expected to contribute reproductively to the population once a dense, healthy forest canopy cover is restored. They are therefore not expected to contribute to the long-term recovery of the species, although they are still protected under the SARA [S. 32].

Common Hoptree is a shade intolerant species, known to be limited in its ability to flower and germinate under forest canopy (Ambrose 2002). As such, occupied forest vegetation types, with the exception of those forming a narrow edge between more open habitats and more broad expanses of forest, were excluded from critical habitat as these areas cannot be expected to contribute to short- or long-term population and distribution objectives but rather may result in local extirpations. Unvegetated beach/bar and bedrock areas are excluded from critical habitat as Common Hoptree tends to establish in areas where substrate stabilization has been initiated by grasses. Open water is also excluded from critical habitat.

Critical habitat has not been identified for Common Hoptree populations (e.g. Walpole Island First Nation populations) at this time where GPS coordinates accurate to 10 m are not currently available. Critical habitat has not been identified for trees that are known to have been planted or transplanted. Records that are older than 20 years (pre 1990), with no verification through follow-up surveys, were deemed historical and were also not considered during critical habitat identification. Existing anthropogenic features are excluded from critical habitat as they are notsuitable habitats for the long-term persistence of this species. These features include, but are not limited to, existing infrastructure (e.g., roads, trails, parking lots, utility corridors, and buildings), existing cultivated areas (e.g. agricultural fields), or unnatural vegetation types (e.g., baseball fields, grassed areas, and septic beds). Areas where Common Hoptrees are found in or adjacent to anthropogenic features (e.g. in utility corridors like hydro, or adjacent to roads and trails etc.) are also excluded from critical habitat in locations where their presence is opportunistically related to the existence of these features (i.e. in locations other than suitable, naturally-occurring vegetation types where the species would be expected to be found without the presence of the anthropogenic feature). Should these anthropogenic features disappear in areas of unsuitable habitat (e.g. through trail, road, or hydro corridor removal or abandonment), the Common Hoptrees present might remain for some time, but would not be expected to continue to reproduce, nor would seedlings be anticipated to germinate under the full canopy cover that would eventually result from natural succession. As on-going maintenance of these areas as suitable habitat for Common Hoptree cannot be guaranteed, and without utility corridor maintenance these areas would quickly become unsuitable for Common Hoptree, these areas cannot be expected to contribute to short- or long-term population and distribution objectives. They are therefore excluded from critical habitat. In addition, it is not believed that these sites are required in order to achieve the population and distribution objectives.

While critical habitat has been identified for 22 of the 35 extant Common Hoptree populations in six of the seven core areas, further work is required to complete critical habitat identification. This work is outlined in Table 4. Further questions may arise as this work proceeds.

Table 4: Schedule of Studies.
Description of Activity Rationale Timeline
Survey extant populations to determine:
  • population size and distribution,
  • type, quality, extent, and environmental variables associated with suitable habitat,
  • population health and reproductive status,
  • threats and their severity, and
  • map and ground truth vegetation community boundaries.
This information is needed to ensure protection of sufficient critical habitat to support the population and distribution objectives and to prioritize critical habitat selection should all areas of habitat not be required to support these objectives. 2011
Assess data collected to determine the features, quantity, and spatial arrangement of critical habitat required, including important limiting resources and conditions. Determine what critical habitat is, how much is required and where it needs to be located within the core areas in order to achieve the population and distribution objectives. 2011
Complete critical habitat modeling and/or identification and delineation by refining critical habitat identification using the most appropriate method(s) (ELC, supervised classification of satellite imagery, aerial photography, tree root zone, and/or other). Complete identification and delineation of critical habitat. 2011

Understanding what constitutes destruction of critical habitat is necessary for the protection and management of critical habitat. Destruction is determined on a case by case basis. Destruction would result if part of the critical habitat were degraded, either permanently or temporarily, such that it would not serve its function when needed by the species. Destruction may result from single or multiple activities at one point in time or from the cumulative effects of one or more activities over time.

Common Hoptree critical habitat may be destroyed by activities that have the following effects:

Examples of activities in or near critical habitat that may result in the destruction of critical habitat include, but are not limited to:

The performance indicators presented below provide a way to define and measure progress toward achieving the population and distribution objectives. Specific progress towards implementing the recovery strategy will be measured against indicators outlined in subsequent action plans. Within five years of final posting, implementation of this recovery strategy will be measured against the following:

One or more action plans related to this recovery strategy will be completed by June 2016, providing details regarding specific recovery measures to be undertaken.

12 Graminoid refers to grasses.

13 ELC is a land and resource classification system that describes and delineates ecosystem units based on ecological factors including vegetation, soil, and geological conditions (Lee et al. 1998).

14 Given that the maximum-recorded dbh for Common Hoptree in Canada is 24 cm (Middle Island, Ontario [Waldron 2003]), the maximum critical root zone is then calculated to be 9 m (24 cm x 36 = 8.64 m rounded up to the nearest metre). This is supported by a 7.9 m rooting radius reported for an 18 year old tree of a species belonging to the same family (Rutaeae) as Common Hoptree (Stone and Kalisz 1990).

15 Diameter at breast height is the diameter of a tree as measured 1.3 m above ground level.

16 ELC Code based on ELC Provincial Catalogue 8 (Lee 2004).

17 Aeolian refers to something of or related to, produced or carried by the wind; in this case, wind-generated.

18 A seral stage is an intermediate phase during ecological succession of an ecosystem as it advances toward its climax community.

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