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Recovery Strategy for the Red Mulberry (Morus rubra) in Canada

7. Critical Habitat Identification

Critical habitat is defined in section 2(1) of SARA 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". This recovery strategy identifies critical habitat range-wide for native Red Mulberry in Canada, to the extent possible at this time based upon the best available information.

Geographical locations of known Red Mulberry trees were obtained from OMNR's NHIC (Figures 6, 7, 9-13, 16, and 19-22) and Ontario Parks (Figures 14 and 19), Parks Canada Agency (Figures 15 and 18), Royal Botanical Gardens (Figure 8), Niagara Peninsula Conservation Authority (Figure 13), Janas et al. (2001; Figure 17), Essex Region Conservation Authority (Figure 24), and Gerry Waldron, M.Sc., Consulting Ecologist (Figure 23). Additional map components were provided by OMNR's Land Information Ontario (Figures 6-24), the North American Atlas (Figures 6-24), Conservation Halton (Figures 6-7), Parks Canada Agency (Figures 15 and 18), Hamilton Region Conservation Authority (Figure 8), Royal Botanical Gardens (Figure 8), and Niagara Peninsula Conservation Authority (Figure 13).

This data was 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. The majority of trees were located during extensive searches in Hamilton, the Regional Municipality of Niagara and Essex County from 2000 to 2001, as part of the Conservation Land Tax Incentive Program for Endangered species in Ontario (Janas et al. 2001, Thompson 2002a). Targeted surveys at various locations were also completed from 2002 to 2004 and in 2007. Where possible, local experts were consulted regarding the continued existence of individual trees, knowledge regarding their genetic purity, accuracy of the data, and missing information.

Critical habitat has been identified for individuals that have been confirmed as pure-strain Red Mulberry trees through genetic testing or that were identified as Red Mulberry (as opposed to hybrid or White Mulberry) trees through morphological evaluation by species experts. Critical habitat has not been identified for trees that have been documented as hybrids through the techniques noted above, or for Red Mulberries that are known to have been planted or transplanted, or that have unverified origins. 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.

Critical habitat is based on UTM (Universal Transverse Mercator coordinate system) locations of individual trees, obtained using a GPS (geographic positioning system) unit. Coordinates, obtained using this technology, are expected to be accurate to approximately 10 m or better. Records obtained by Paul O’Hara from the Clappison Escarpment Woods, Waterdown Escarpment Woods, and Borer’s Creek Conservation Area/Rock Chapel Escarpment/Berry Tract populations have been excluded from consideration in critical habitat identification at this time, as data points have been determined to have an accuracy no better than 80- 100 m (N. Finney pers. comm. 2010).

Critical habitat is identified as a circle with a radius of 15 m surrounding the trunk of each live, individual, naturally occurring Red Mulberry tree, encompassing a critical habitat area of 707 m2 around each tree (see Figure 3). 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 (dbh - i.e. the diameter of a tree 1.3 m above ground level) of a tree (Johnson 1997). Given that the maximum-recorded dbh for Red Mulberry in Canada is 40 cm (Farrar 1995), the maximum critical root zone is then calculated to be 15 m (40 cm x 36 = 14.4 m rounded up to the nearest metre). This is supported by a 12.7 m rooting radius reported for a mature White Mulberry tree (dbh not provided) (Stone and Kalisz 1990), which occurs in the same genus as Red Mulberry. To be precautious, the larger of the two values has been applied in the identification of critical habitat.

Figure 3: Conceptual Illustration of Critical Habitat (15 m Radius Tree Root Zone) around a Single Red Mulberry Tree

Figure 3. 15 m radius tree root zone

For locations where more than one Red Mulberry tree occurs, critical habitat also includes all Forest12, Woodland13, and Talus14 ELC community classes15 that fall within a shape, identified as the area within which critical habitat is found on the critical habitat maps, that encompasses the tree root zone of all Red Mulberry trees that are within 999 m or less of another Red Mulberry tree (see Figure 4A). On Middle Island, critical habitat also includes the Cultural Meadow/Cultural Thicket ELC community series, as this community is in the process of regenerating from former anthropogenic uses and is expected to succeed to woodland and eventually forest. The area within which critical habitat is found is represented by a minimum convex polygon16 around all Red Mulberry tree root zones falling within 999 m or less of another Red Mulberry tree at that location (see Figure 4B). One kilometre is considered the minimum separation distance needed to place trees into two separate populations rather than a single one (NatureServe 2010). As such, the 999 m value has been selected to ensure protection of all suitable habitats between trees within a Red Mulberry population.

Figure 4: Conceptual Illustration of A) the Area within which Critical Habitat is Found for Locations that have Two or More Red Mulberry Trees Separated by 999 m or Less and B) a Distance Greater than 999 m Between Red Mulberry Trees Resulting in Separate Polygons Related to Critical Habitat for Each Population

Figure 4. Conceptual illustration of A) the area within which critical habitat is found for locations that have two or more Red Mulberry trees separated by 999 m or less and B) a distance greater than 999 m between Red Mulberry trees resulting in separate polygons related to critical habitat for each population.

Across the species' range, the biophysical attributes of Red Mulberry critical habitat include moist, but well-drained, areas that have tree cover greater than 35% (Forest and Woodland ELC community classes). This includes:

  • floodplains and river valleys,
  • areas where additional light penetrates the tree canopy (e.g. forest gaps and edges),
  • Essex County, including Point Pelee National Park, Pelee, Middle, and East Sister Islands and the Municipality of Chatham-Kent: moist swales in sandy soils,
  • Niagara Escarpment and Peninsula: limestone-based, loamy soils, plus the Talus ELC community class in areas, especially along benches (flat areas) in the escarpment, where moisture levels remain high.

General locations of Red Mulberry critical habitat are shown in Figure 5. Site-specific critical habitat maps for 22 critical habitat parcels are provided in Appendix B. Where a Red Mulberry tree exists within 999 m of another Red Mulberry tree, the area within which critical habitat is found has been mapped. Only the areas within this boundary that meet the biophysical description of critical habitat outlined in this section are critical habitat.

Existing anthropogenic features are excluded from critical habitat as they are not suitable habitats for the long-term persistence of this species. These features include, but are not limited to existing infrastructure (e.g. roads, trails, and parking lots), existing cultivated areas (e.g. agricultural fields), and unnatural vegetation types (e.g. grassed areas and septic beds). In addition, all White Mulberry trees and hybrid mulberry trees are excluded from critical habitat as optimal habitat for Red Mulberry should be free from these trees.

Figure 5: General Locations of Critical Habitat for Red Mulberry in Canada

Figure 5: General locations of critical habitat for Red Mulberry in Canada.

7.1 Activities Likely to Result in the Destruction of Critical Habitat

Examples of activities, in or near critical habitat, likely to destroy critical habitat include, but are not limited to those outlined in Table 4 below.

Table 4: Examples of Activities Likely to Result in the Destruction of Critical Habitat

Effect of an Activity that May Destroy Critical HabitatExamples of Activities likely to Destroy Critical Habitat
Loss or fragmentation of critical habitat.Anthropogenic development within critical habitat (e.g. agricultural activities such as land clearing and/or tilling of the soil, industrial or residential development, or infrastructure developments such as new road, pipeline, water main, and wind power construction) or high intensity logging within critical habitat (clearing paths or other areas for log removal and/or stockpiling).
Damage to canopy or understory vegetation, increased evaporation leading to drying of the soil or soil compaction (which may result in reduced establishment of Red Mulberry recruits).Logging - removal of trees within critical habitat using practices that do not conform to low impact logging standards (e.g. Forest Stewardship Council 2004). Examples of logging activities that are likely to destroy critical habitat include clear-cutting, high-grading, and diameter limit cuts.
Alteration of drainage patterns, ground water flow and soil moisture levels within critical habitat.Property drainage (e.g. for agriculture or residential or industrial development) in or adjacent to critical habitat.
Alteration of forest vegetation resulting in increased hybridization with White Mulberry or hybrid mulberry trees and reduced production of pure Red Mulberry seed.Intentional planting of White Mulberry plants within critical habitat.
Increased shading, or alteration of forest canopy or understory vegetation, leading to competition with Red Mulberry seedlings or saplings.Intentional planting of non-native species within critical habitat.
Disturbance of soil (which may result in increased establishment of exotic plants) and/or destruction of vegetation.Vandalism or off-road vehicle use within critical habitat.

7.2 Schedule of Studies to Identify Critical Habitat

Additional work required to refine the population and distribution objectives and determine if critical habitat identification requires modification to support these objectives for recovery is outlined in Table 5.

Table 5: Schedule of Studies for the Identification of Critical Habitat

Description of Research ActivityExpected ResultsEstimated Timeline From Final Recovery Strategy Posting
Confirm status of Red Mulberry populations and individual trees where necessary.Update information on Red Mulberry population sizes and the presence/ absence of individual trees.3 years
Search suitable habitat (Niagara Escarpment, Brock University lands, Essex County, historic sites etc.) for Red Mulberry trees that have not previously been located.Improve knowledge of current distribution and abundance.4 years
Complete ELC surveys of extant populations of Red Mulberry.Vegetation communities are identified in areas surrounding existing trees, ground-truthed and mapped to the extent possible for all extant sites contributing to critical habitat definitions.4 years
Confirm the genetic purity of trees identified as Red Mulberry.Confirm the genetic purity of trees previously identified using morphological characteristics and separate true Red Mulberry trees from M. murrayana in order to confirm which individual trees require critical habitat protection.5 years
Complete critical habitat modeling and/or identification and delineation.Refine the population and distribution objectives based upon the above information if necessary. Identify optimal Red Mulberry habitat and modify critical habitat required to support the population and distribution objectives for the Canadian Red Mulberry population if necessary.6 years

12 Forests have a tree cover greater than 60%.
13 Woodlands have a tree cover greater than 35% and less than or equal to 60%.
14 Talus are slopes of rock rubble at the base of cliffs where coarse, rocky debris makes up more than 50% of the substrate surface and there is an average substrate depth of less than 15 cm.
15 A Community Class is an organizational level with the ELC system of classification that groups plant communities based on similar, generalized ecological patterns and processes.
16 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 any two points (in this case, Red Mulberry trees with their 15 m tree root zone). As an analogy, picture an elastic stretched around a group of pegs on a peg board.