Recovery Strategy for the Dwarf Hackberry in Canada [Proposed] 2011: Critical Habitat

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 Dwarf Hackberry 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 Dwarf Hackberry trees were obtained from Norris (1994), Brownell and Blaney (1995), Mills and Craig (2008), Ambrose (unpub. data), Ausable Bayfield Conservation Authority (unpub. data), OMNR (unpub. data), Nature Conservancy of Canada (unpub. data), NHIC (unpub. data), and Parks Canada Agency (unpub. data). Additional map components were provided by OMNR’s Land Information Ontario and the North American Atlas (Figures 4 – 12, 14, and 16), Ausable Bayfield Conservation Authority (Figures 6 and 9), St. Clair Region Conservation Authority (Figures 10 and 11), Nature Conservancy of Canada (Figures 5 and 10), and Dougan and Associates (2007) and Parks Canada Agency (Figure 4).

Across the species’ range, the biophysical attributes of Dwarf Hackberry 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:

• dry, sandy, well-drained sites with open, early successional habitats near the shores of:
• Lake Erie: along the leading edge of woody, shoreline vegetation adjacent to woodland or forest and in adjacent shrub and/or treed sand dune, shrub shoreline, and deciduous thicket communities at Point Pelee National Park (Jalava et al. 2008) and Fish Point (Pelee Island),
• Lake Huron: at inland, ancient Lake Warren dune sites in tallgrass savanna communities and along dry oak/pine woodland and forest edges, in natural forest canopy gaps, on the tops of dune ridges and mounds, and on steep, south-facing dune slopes from Grand Bend to Kettle Point (Lambton County – Dunster 1992, Mills and Craig 2008) and,
• Hastings County (Stirling Slope Complex ANSI): on kame ridge top prairie and savanna remnants above the Trent River along the ancient Lake Iroquois shoreline (Brownell and Blaney 1995), and
• open woods, maintained by extreme droughty conditions, on dry, calcareous, alvar and/or treed rock barren sites at Point Anne Alvar, the Salmon River Alvar ANSI (Lonsdale), and historically in the interior of Pelee Island (Red Cedar Savanna) (Norris 1994, Ambrose 2003, NHIC 2010a, 2010b, 2010c).

General locations of Dwarf Hackberry critical habitat are shown in . Site-specific critical habitat maps for 20 critical habitat parcels, covering the six extant populations, are provided in Appendix B.

Ecological Land Classification Vegetation Type Mapping

Occupancy-based approaches were used to identify critical habitat for the Dwarf Hackberry across its Canadian range: Where data were available to identify a Dwarf Hackberry tree or trees within one or more Ecological Land Classification¹⁰ (ELC) vegetation types, critical habitat was identified as the boundaries of the occupied ELC vegetation type(s), provided that they were considered suitable for survival or recovery of the species, as follows:

• Point Pelee National Park, Leamington, Essex County, Ontario (critical habitat parcel #247_3, Figure 4): the occupied Red Cedar Treed Sand Dune and Hoptree Shrub Sand Dune ELC vegetation types adjacent to the shores of Lake Erie (Lee 2004, Dougan & Associates 2007, Jalava et al. 2008).
  
• Van Valkenburg property (Lambton County), Lambton Shores, Lambton County, Ontario (parcel #247_4, Figure 5): the occupied Dry Black Oak – Pine Tallgrass Savanna ELC vegetation type (Nature Conservancy of Canada unpubl. data).

10 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).

• Port Franks Properties (Lambton County), Port Franks, Lambton County, Ontario (parcel #247_11, Figure 6): the ELC vegetation type labelled PFP06 (Ausable Bayfield Conservation Authority unpub. data). Given that the specific ELC vegetation type associated with the PFP06 polygon has not yet been defined, only the areas within this boundary that meet the biophysical description of critical habitat outlined in this section are considered critical habitat.

Other Types of Habitat Mapping

When ELC data was not available, other types of available habitat mapping were used to identify Dwarf Hackberry critical habitat, as follows:

• Salmon River Alvar ANSI (Lonsdale), Lonsdale, Hastings County, Ontario (parcel #247_20, Figure 7): the occupied Very Dry Treed Barrens on Limestone Bedrock plant community (Norris 1994, Ambrose 2003).
  
• Stirling Slope Complex ANSI, Frankford, Hastings County, Ontario (parcel #247_13, #247_15, and 247_17, Figure 8): vegetation community 2e, a Kame Ridge Top Dry-Mesic Prairie Remnant and vegetation community 3e, Kame Ridge Top Savannas (Brownell and Blaney 1995, Ambrose 2003). Additional critical habitat and an area within which critical habitat is found are identified within this ANSI based on the known locations of individual trees (Parks Canada Agency unpub. data).

Critical Habitat Based on Observations of Trees

Areas of Dwarf Hackberry Occurrence

Where no vegetation community mapping was available, but areas of Dwarf Hackberry occurrence had been mapped within the last 20 years, these areas were identified as critical habitat, as follows.

• Ausable River Cut (formerly Thedford) Conservation Area (Lambton County), Northville, Lambton County, Ontario (parcel #247_10, Figure 9): the Dwarf Hackberry area delineated on the property in Mills and Craig (2008).
  
• Lambton County Heritage Forest (Lambton County), Port Franks, Lambton County, Ontario (parcel #247_9, Figure 10): vegetation unit 3B (Mills and Craig 2008). An additional area within which critical habitat is found is identified on this property based on the known locations of individual trees (Nature Conservancy of Canada unpub. data).
  
• L-Lake Management Area (Lambton County), Port Franks, Lambton County, Ontario (parcel #247_6, Figure 11): the Dwarf Hackberry area delineated on the property in Mills and Craig (2008). An additional area of critical habitat is identified on this property based on the location of a few trees near the entrance to the property (Mills and Craig 2008).

Point Data Representing Dwarf Hackberry Occurrences

Dwarf Hackberry is a moderately shade intolerant species that does not typically occur within closed canopy forest. Forest succession and canopy closure creates unsuitable habitat that can result in local extirpations. ELC and other available mapped vegetation community data are not detailed enough within forested habitats to identify tree gaps, southern facing slopes, dune ridges, and ecotones or open edges that provide localized suitable habitat. As such, occupied ELC forest vegetation types have been excluded from critical habitat. Instead, where possible, an occupancy approach, based on the observation of trees, was applied, as it is better able to represent localized microhabitats in the forest that are suitable for Dwarf Hackberry. Where habitat data are not available or suitable (e.g. closed canopy forest) and areas of the species’ occurrence have not been mapped, critical habitat is 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.

Critical habitat is identified as a circle with a radius of 9 m surrounding the trunk of each known, live, individual, naturally occurring Dwarf Hackberry tree (see Figure 12) at identified locations. This is based on a critical root zone definition, used as a zone of protection for trees, of up to 36 times the diameter at breast height (dbh¹¹) of a tree (Johnson 1997). Given that the maximum recorded dbh for Dwarf Hackberry in Canada is 22.5 cm (Lambton County Heritage Forest [Lambton County], Ontario [Dunster 1992]), the maximum critical root zone is then calculated to be 9 m (22.5 cm x 36 = 8.10 m rounded up to the nearest metre). This approach was applied to create two critical habitat parcels in Hastings County, Ontario: #247_19 at Point Anne Alvar, Point Anne (Figure 12 – NHIC unpub. data) and #247_14 at Stirling Slope Complex ANSI, Frankford (Figure 8 – Parks Canada Agency unpub. data).

For single data points representing more than one Dwarf Hackberry tree, the number of trees that the point represents was multiplied by the critical habitat area for a single tree (p r² = p 92 = 254 m² rounded to the nearest m²), and then dividing by pi (p). The square root of the result, rounded to the nearest metre, was then applied as the radius of the tree root zone around the known GPS data point in order to delineate an area within which critical habitat is found for the number of trees in that cluster. Critical habitat within this area is represented by any area satisfying any one of the biophysical attributes of critical habitat previously described along with the full tree root zone of each individual tree falling within this area (this tree root zone may extend beyond the area within which critical habitat is found). This approach was applied to create critical habitat parcel #247_5 (Figure 11) at L-Lake Management Area, Port Franks, Lambton County, Ontario (Lambton County – Mills and Craig 2008) and parcel #247_2 (Figure 14) along the municipal right of way at Fish Point, Pelee Island, Ontario (Pelee Island – OMNR unpub. data).

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

For locations where more than one Dwarf Hackberry data point exists:

• Watson Property (Lambton County), Port Franks, Lambton County, Ontario (parcel #247_7, Figure 10): (Nature Conservancy of Canada unpub. data),
  
• Lambton County Heritage Forest (Lambton County), Port Franks, Lambton County, Ontario (parcel #247_8, Figure 10): (Nature Conservancy of Canada, unpub. data),
  
• Stirling Slope Complex ANSI, Frankford, Hastings County, Ontario (parcel #247_16, Figure 8): (Parks Canada Agency unpub. data), and
  
• Point Anne Alvar, Point Anne, Hastings County, Ontario (parcel #247_18, Figure 12): (Ambrose 2003, NHIC unpub. data),

the area within which critical habitat (based on biophysical attributes) is found also includes all habitats, excluding wetlands, that fall within a shape that encompasses the tree root zone of all Dwarf Hackberry trees or clusters of trees for which data points exist (see Figure 15A). In these instances, the area within which critical habitat is found is represented by a minimum convex polygon¹² around all known Dwarf Hackberry tree root zones falling within 100 m or less of another known Dwarf Hackberry tree within that critical habitat parcel (see Figure 15B). This 100 m separation distance was chosen to afford some level of protection to critical habitat between Dwarf Hackberry individuals clustered at a site until such time as critical habitat identification can be completed.

12 A minimum convex polygon is the smallest shape, drawn with straight line segments, which will surround all straight line segments that can be drawn between the outside edges of the tree root zones of two trees within a Dwarf Hackberry population. As an analogy, picture an elastic stretched around a group of pegs on a peg board.

Within Fish Point Provincial Nature Reserve (Pelee Island) (parcel #247_1, Figure 14) and The Pinery Provincial Park, Lambton Shores (Lambton County) (parcel #247_12, Figure 16), an area within which critical habitat is found is delineated as a circle of 9 m radius surrounding the trunk of each individual, naturally occurring Dwarf Hackberry within each park, plus all habitats within a shape that encompasses the tree root zone of all Dwarf Hackberry trees that are within 100 m from one or more other Dwarf Hackberry trees, excluding wetlands, which are unsuitable habitat. The area within which critical habitat is found has been mapped.

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, including 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. grassed areas and septic beds) are excluded from critical habitat as they are not suitable habitats for the long-term persistence of this species. Areas where Dwarf Hackberry trees 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 Dwarf Hackberry trees 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 Dwarf Hackberry individuals cannot be guaranteed, and without utility corridor maintenance these areas would quickly become unsuitable for Dwarf Hackberry, these areas cannot be expected to contribute to short- or long-term population and distribution objectives. 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 each of the six Dwarf Hackberry populations, further work is required to refine critical habitat identification and determine if additional critical habitat is required to achieve the population and distribution objectives for the species. This work is outlined in Table 4 below.

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 a single or multiple activities at one point in time or from the cumulative effects of one or more activities over time.

Dwarf Hackberry critical habitat may be destroyed by activities that have the following effects:

• loss or fragmentation of critical habitat,
• alteration of the natural processes or disturbance regimes within or outside of critical habitat, including coastal and aeolian (wind-generated) processes that affect sand deposition or accretion and erosion rates or the seral¹³ stage of vegetation communities within critical habitat;
• excessive alteration of the canopy cover (resulting in increased shading or sun scald with excessive canopy removal) or the understory vegetation (resulting in the loss of germination sites) within critical habitat, and
• soil compaction within critical habitat.

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

• development or construction of new infrastructure within critical habitat (homes; sheds; industrial or other buildings; roads, trails, and paths [logging purposes included]; parking lots, clearings, and areas for stockpiling timber; pipelines and water mains; sewage systems; wind power structures; etc.) or adjacent to critical habitat (docks, piers, groynes, or shoreline hardening structures etc. that will affect the delivery of sediment to critical habitat);
• upgrades or maintenance to existing infrastructure within critical habitat (e.g. building additions, cutting, trimming, or removal of vegetation that has not met environmental assessment requirements) or adjacent to critical habitat (modifications to docks, piers, groynes, or shoreline hardening structures etc. that will affect the delivery of sediment to critical habitat);
• aggregate extraction (e.g. sand or limestone quarrying within critical habitat or offshore sand mining near critical habitat that alters sand deposition rates in critical habitat);
• agricultural activities within critical habitat (land clearing, tilling soil, livestock grazing);
• the removal of trees within critical habitat using practices (e.g. clear-cutting, high-grading, and diameter limit cuts) that do not conform to low impact logging standards (e.g. Forest Stewardship Council 2004),
• unregulated use of off-road vehicles or other acts vandalism within critical habitat;
• removal of large quantities of associated native species or whole habitats within critical habitat (e.g. through beach grooming, cutting, mowing, or raking that results in sun scald to Dwarf Hackberry trees or the loss of suitable seedling germination sites); and
• deliberate planting of non-indigenous (exotic) or invasive species into critical habitat.

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

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:

• the Point Pelee National Park Dwarf Hackberry population trend is stable;
• the six Canadian Dwarf Hackberry populations have been maintained at the following approximate population sizes (all age classes included):
• Pelee Island: 12 (OMNR unpub. data),
• Point Pelee National Park (mainland): 47 (Jalava et al. 2008),
• Lambton County: 13 083 (Mills and Craig 2008, MacKenzie pers. comm. 2010, Ausable Bayfield Conservation Authority unpub. data, Nature Conservancy of Canada unpub. data),
• Point Anne Alvar: 10 (Ambrose 2003, NHIC unpub. data)
• Stirling Slope Complex ANSI: 54 (Ambrose 2003, Parks Canada Agency unpub. data), and
• Salmon River Alvar ANSI (Lonsdale): 5 (Ambrose 2003); and
• Dwarf Hackberry habitat suitability, as defined in the biophysical characteristics of critical habitat in Section 7.1, has been maintained in areas identified as critical habitat.

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.