Rigid Apple Moss (Bartramia aprica): COSEWIC assessment and status report 2023

Official title: COSEWIC assessment and status report on the Rigid Apple Moss (Bartramia aprica) in Canada

Committee on the status of Endangered Wildlife in Canada (COSEWIC)
Threatened 2023

COSEWIC assessment summary

Assessment summary – December 2023

Common name

Rigid Apple Moss

Scientific name

Bartramia aprica

Status

Threatened

Reason for designation

This moss occurs in Canada in the Mediterranean climates of southern Vancouver Island and the Gulf Islands. It is restricted to rock outcrops and well-drained, shallow soil in close association with seepages, almost all within imperiled Garry Oak ecosystems. Increased survey effort has shown that the species is more widespread than previously known, reducing its risk of extirpation. However, the population remains small, and habitat loss through climate change, fire and fire suppression, and invasive non-native species continues to threaten the species.

Occurrence

British Columbia

Status history

Designated Threatened in April 1997. Status re-examined and designated Endangered in May 2000 and November 2009. Status re-examined and designated Threatened in December 2023.

COSEWIC executive summary

Rigid Apple Moss

Bartramia aprica

Wildlife species description and significance

Rigid Apple Moss is a green to yellow-green moss that grows in tufts. It has a spherical sporangium (spore capsule) when young (until maturity) and linear leaves that are straight and erect in both the wet and dry states.

In Canada, where the species reaches its northern global range limit, it is restricted to Garry Oak and associated ecosystems, which are considered “Critically Imperiled” in Canada.

Distribution

The taxonomy of Rigid Apple Moss changed recently due to new molecular analyses: the species found in Canada is restricted to the west coast of North America and also to Mediterranean climates in Europe. In Canada, just thirteen subpopulations are known, on southeastern Vancouver Island and the adjacent Gulf Islands of British Columbia. Besides one known record of Rigid Apple Moss in Washington state, the Canadian population shows a significant disjunction from the centre of the species’ North American distribution in California.

Habitat

Populations of Rigid Apple Moss are typically associated with warm, dry summers and mild, wet winters. Most subpopulations have a southern aspect. The Canadian population of Rigid Apple Moss occupies two distinct microhabitats, both of which are free of grass and herb cover: (1) well-drained, shallow, compacted soil, and (2) crevices or undersides of small overhanging lips of meta-igneous bedrock. Rigid Apple Moss subpopulations are closely associated with seepage and often occur in, or close to, intermittently and/or seasonally moist outflow paths.

Biology

Rigid Apple Moss disperses primarily as spores that result from sexual reproduction. Rigid Apple Moss is a small, upright moss, producing reproductive structures at the end of stems or branches. Male and female reproductive structures co-occur on the same plant. Although the Canadian population appears to produce spores successfully and regularly, dispersal is expected to be mainly local, and dispersal between subpopulations is unlikely. The species has an estimated generation time of 11 to 25 years.

Population sizes and trends

In Canada, there are 12 extant Rigid Apple Moss subpopulations and one extirpated subpopulation. Trends in the size and density of each Rigid Apple Moss subpopulation are difficult to estimate, owing to the incomplete nature of historical records and the inconsistent observation history. Three of the extant subpopulations have been monitored every eight to ten years, and one has been monitored almost annually. Most other subpopulations have had at least one baseline survey.

Threats and limiting factors

Reliance on a narrow range of specific micro- and macro-habitat requirements is the main limiting factor for Rigid Apple Moss. Rigid Apple Moss is particularly sensitive to climate change because of its close association with rare macro- and micro-climatic patterns. These are projected to shift, with more severe and frequent temperature and precipitation extremes experienced in the future. This sensitivity is supported by the NatureServe Climate Change Vulnerability Index which showed the species to be Extremely Vulnerable, a result that strongly supports the Threats Assessment score for climate change.

Other high-impact threats—fire suppression, wildfire, and invasive species—are exacerbated by climate change. Lower impact threats such as residential and commercial development and human intrusion and disturbance (that is, recreation, military exercises, and work) are more restricted in scope or are less imminent. In recent years the species’ habitat type has been destroyed and degraded by urban development.

Protection, status, and ranks

Rigid Apple Moss was listed as Endangered in 2003 under the Species at Risk Act (SARA), with three subpopulations on federal land protected under the act. In British Columbia, it is characterized as S2 (Imperiled) and is assigned to the Red List. It receives some protection in provincial Ecological Reserves (ERs) and parks (three subpopulations), on properties with conservancy covenants or in ecological reserves (three subpopulations), and in a Capital Regional District Park (one subpopulation).

Technical summary

Bartramia aprica

Rigid Apple Moss

Bartramie à feuilles dressées

Range of occurrence in Canada (province/territory/ocean): British Columbia

Demographic information

Generation time (usually average age of parents in the population; indicate if another method of estimating generation time indicated in the IUCN guidelines (2012) is being used)

11 to 25 years; 3 generations = 50 years based on long lived species (Bergamini et al. 2019)

Is there an [observed, inferred, or projected] continuing decline in number of mature individuals?

Yes, inferred. one subpopulation is presumed extirpated (Ash Point), and there has been an observed decrease in colonies at Observatory Hill. Climate change and other threats are inferred to cause additional declines in the number of mature individuals within 3 generations. (Threat impact as assessed in the Threats Calculator is Very high).

Estimated percent of continuing decline in total number of mature individuals within [5 years or 2 generations]

Unknown. The total number of mature individuals has not been monitored.

[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the last [10 years, or 3 generations].

Unknown.

[Projected or suspected] percent [reduction or increase] in total number of mature individuals over the next [10 years, or 3 generations].

Unknown.

[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over any [10 years, or 3 generations] period, over a time period including both the past and the future.

Unknown

Are the causes of the decline a. clearly reversible and b. understood and c. ceased?

The cause of the extirpation at Ash Point is understood but whether or not it is reversible is unknown. The causes of inferred future losses are not likely reversible, they are understood, but have not ceased.

Are there extreme fluctuations in number of mature individuals?

No

Extent and occupancy information

Estimated extent of occurrence (EOO)

2980 km²

Index of area of occupancy (IAO)

(Always report 2x2 grid value).

52 km²

Is the population “severely fragmented” that is, is >50% of its total area of occupancy in habitat patches that are (a) smaller than would be required to support a viable population, and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse?

No. The habitat patches are large enough to support viable subpopulations, although the distance between habitat patches is greater than the species can be expected to disperse.

Number of “locations” (use plausible range to reflect uncertainty if appropriate)

The most plausible number of locations is 1-13, based on the threat of climate change which impacts Rigid Apple Moss directly and exacerbates other threats such as invasive species and wildfire frequency.

Is there an [observed, inferred, or projected] decline in extent of occurrence?

Possibly, the threats of climate change, fire, fire suppression, and invasive species are inferred to reduce the extent of occurrence.

Is there an [observed, inferred, or projected] decline in index of area of occupancy?

Yes, the threats of climate change, fire, fire suppression and invasive species are inferred to reduce the area of occupancy.

Is there an [observed, inferred, or projected] decline in number of subpopulations?

Yes, observed and projected. The Ash Point subpopulation is presumed extirpated and there has been an observed decrease in colonies and colony health at Observatory Hill. The threats of climate change, fire, fire suppression, and invasive species are inferred to reduce the number of subpopulations.

Is there an [observed, inferred, or projected] decline in number of “locations”?

Yes, observed and projected, the threats of climate change, fire, fire suppression, and invasive species, threaten the species in Canada.

Is there an [observed, inferred, or projected] decline in [area, extent and/or quality] of habitat?

Yes, the threats of climate change, fire, fire suppression, and invasive plants are inferred to reduce the area, extent, and quality of habitat.

Are there extreme fluctuations in number of subpopulations?

No

Are there extreme fluctuations in number of “locations”?

No

Are there extreme fluctuations in extent of occurrence?

No

Are there extreme fluctuations in index of area of occupancy?

No

Number of mature individuals (in each subpopulation)

Subpopulations (give plausible ranges) /N Mature Individuals (Colonies)

British Columbia Parks Ecological Reserve (and area west of ER), Lasqueti Island British Columbia (LAS)

~260 to 560

Mount Maxwell, SaltSpring Island (MAX)

15

Reginald Hill, SaltSpring Island (REH)

118+

Mount Tuam, SaltSpring Island (TUA)

40

Musgrave Rock, SaltSpring Island (MUR)

30+

Oaks Bluff, Pender Island (OAB)

NR

Wymond Point, Sidney Island (SID)

>96

Government House, Vancouver Island (GOH)

19+

Mount Finlayson, Vancouver Island (FIN)

19+

Observatory Hill, near Saanich, Vancouver Island (OBS)

24

Notch Hill (CFMETR), near Nanoose, Vancouver Island (NOH)

~240

Mary Hill (CFMETR), near Metchosin, Vancouver Island (MRH)

>275

Total

>1,136+

“+” Indicates that the surveyors believe additional colonies are present (for example, ample unsurveyed habitat combined with ease of locating additional colonies during survey). “>” indicates the number is a lower limit. “~” indicates an estimate of the total number. “NR” indicates a value was not reported.

Quantitative analysis

Is the probability of extinction in the wild at least [20% within 20 years or 5 generations, or 10% within 100 years]?

None completed

Threats (direct, from highest impact to least, as per IUCN Threats Calculator)

Was a threats calculator completed for this species?

Yes

See section on Threats and Limiting factors in this report for details. The following list summarizes the threats identified for Bartramia aprica subpopulations in British Columbia in approximate descending order of importance based on the completed Threats Assessment (Appendix 1) and Climate Change Vulnerability Index (CCVI; Appendix 2)

Overall threat impact is Very high

1. 11.0 Climate change and severe weather (Impact = High)
2. 7.0 Natural system modifications (Impact = High)
3. 8.0 Invasive and other problematic species and genes (Impact = High)
4. 1.0 Residential and commercial development (Impact = Low)
5. 6.0 Human intrusion and disturbance (Impact = Low)

What additional limiting factors are relevant?
Limited dispersal ability, reliance on a limited, at-risk habitat type, and narrow microhabitat specificity.

Rescue effect (immigration from outside Canada)

Status of outside population(s) most likely to provide immigrants to Canada.

Nearest non-Canadian population is 300 km away, in Washington State (single occurrence). No status assessment of the species is reported for Washington or California, but in the US, it is considered N1/N2.

Is immigration known or possible?

Unlikely

Would immigrants be adapted to survive in Canada?

Unknown

Is there sufficient habitat for immigrants in Canada?

Unknown

Are conditions deteriorating in Canada?

Yes

Are conditions for the source (that is, outside) population deteriorating?

Unknown

Is the Canadian population considered to be a sink?

No

Is rescue from outside populations likely?

Unlikely due to distance, in the context of limited dispersal ability

Data sensitive species

Is this a data sensitive species?

No

Status history

Designated Threatened in April 1997. Status re-examined and designated Endangered in May 2000 and November 2009. Status re-examined and designated Threatened in December 2023.

Status and reasons for designation:

Status:

Threatened

Alpha-numeric codes:

C2a(i)

Reasons for designation:

This moss occurs in Canada in the Mediterranean climates of southern Vancouver Island and the Gulf Islands. It is restricted to rock outcrops and well-drained, shallow soil in close association with seepages, almost all within imperiled Garry Oak ecosystems. Increased survey effort has shown that the species is more widespread than previously known, reducing its risk of extirpation. However, the population remains small, and habitat loss through climate change, fire and fire suppression, and invasive non-native species continues to threaten the species.

Applicability of criteria

Criterion A (Decline in total number of mature individuals):

Not applicable. The rate of decline in number of mature individuals is unknown although there is an inferred continuing decline of uncertain magnitude.

Criterion B (small distribution range and decline or fluctuation):

Not applicable. EOO of 2980 km² and IAO of 52 km² are below the threshold for Endangered, but the population is not severely fragmented, occurs at >10 locations, and does not experience extreme fluctuations.

Criterion C (Small and declining number of mature individuals):

Meets Threatened, C2a(i), with <10,000 mature individuals, no subpopulation >1000 mature individuals, and a projected decline in the number of individuals.

Criterion D (Very small or restricted population):

Not applicable. Number of mature individuals (1,136+), IAO (>20 km²) and number of locations (>10) exceed thresholds for D1 and D2.

Criterion E (Quantitative analysis):

Not applicable. Analysis not conducted.

Preface

Since the last COSEWIC status report in 2009, the taxonomy of Rigid Apple Moss (formerly known by the scientific name Bartramia stricta) has changed based on the results of molecular and morphological analyses showing that what was understood to be one taxon consists of several species. Only one of these species, Bartramia aprica, occurs in Canada (Müller 2014). However, other work shows the western North American Bartramia aprica to comprise several taxa (Damayanti et al. 2012; Neumann et al. 2019), including a new taxon, Bartramia rosamrosiae. The results of these studies also show that the taxon present in Canada, Bartramia cf. rosamrosiae, occupies only the cooler, wetter regions of California (the Sierra Nevada, and northern California).

The heightened profile of the species in British Columbia since it was declared Endangered in Canada has prompted increased search effort, which has resulted in the discovery of seven new subpopulations and also increased the known extent of occurrence (EOO) and index of area of occupancy (IAO) since the last COSEWIC assessment.

In Canada, the species’ distribution is limited to southwestern British Columbia, in Garry Oak and associated ecosystem habitats, which are known to be rare and have been assessed as “Critically Imperiled” in Canada. The three largest Rigid Apple Moss subpopulations (located on federal land and in a British Columbia Ecological Reserve) account for most of the known Canadian population (>68% of individuals) and appear to be stable (Sadler 2011; McIntosh 2012; McIntosh and Miles 2013; McIntosh and Joya 2018a,b). One subpopulation is considered extirpated, one has not been confirmed since its initial discovery, and at least one appears to be declining in health and number of colonies.

COSEWIC history

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2019)

Wildlife species

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)

A wildlife species that no longer exists.

Extirpated (XT)

A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)

A wildlife species facing imminent extirpation or extinction.

Threatened (T)

A wildlife species likely to become endangered if limiting factors are not reversed.

Special concern (SC)
(Note: Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.)

A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at risk (NAR)
(Note: Formerly described as “Not In Any Category”, or “No Designation Required.”)

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data deficient (DD)
(Note: Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” [insufficient scientific information on which to base a designation] prior to 1994. Definition of the [DD] category revised in 2006.)

A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

The Canadian Wildlife Service, Environment and Climate Change Canada, provides full administrative and financial support to the COSEWIC Secretariat.

Wildlife species description and significance

Name and classification

Scientific name: Bartramia aprica Müll. Hal.

Bibliographic citation: Linnaea 39: 397. 1875.

Common name: Rigid Apple Moss

Family name: Bartramiaceae

Major plant group: Mosses

The taxonomy of Rigid Apple Moss has seen significant recent revision based on the results of molecular and morphological analyses. Damayanti et al. (2012) assessed the global population structure within B. stricta and determined that Northern Hemisphere specimens were distinct from those in the Southern Hemisphere. They described the taxon in the Northern Hemisphere (the “Mediterranean” species) as Bartramia rosamrosiae. Müller (2014) later showed that the correct name for the Mediterranean taxon, based on taxonomic precedence, is B. aprica. However, recent molecular and morphological analysis indicates further taxonomic differentiation within North America; western North American populations formerly understood to be B. aprica actually represent two distinct species: B. aprica and B. cf. rosamrosiae (Damayanti et al. 2012; Neumann et al. 2019). Only the latter occurs in Canada. However, since the work of Neumann et al. (2019) remains so far largely unpublished, this report retains the name B. aprica for the taxon that is present in Canada.

Damayanti et al. (2012) provide a description, summarized as follows: B. aprica is a small erect plant (stem < 40 mm) that grows in dense tufts (cover picture and Figure 1). It is green above and reddish-brown below, with reddish rhizoids covering most of the basal stem. Stems are simple or branched (in a parallel manner with branches 7 to 20 mm long). Leaves are long, triangular and stiffly erect, and appressed when dry (sometimes bending to one side) and erect to spreading when moist. B. aprica is synoicous (that is, both male and female reproductive structures occur in the same inflorescence). The capsule is erect, ovoid to globose in shape, and lightly ribbed when mature and dry. The spores are 22 µm to 32 µm in diameter. The characteristically straight erect leaves and the green, spherical, smooth young sporangium of B. aprica contribute to its common name (Rigid Apple Moss).

Figure 1. Habit of Rigid Apple Moss: (a) illustration of Rigid Apple Moss (synonymous with B. stricta in Flora of North America Association 2008) showing size and characteristics of leaves and sporophytes, and (b) close-up view of Rigid Apple Moss, showing sporophytes with young, spherical capsules (photo from McIntosh 2008, used with permission).

Population spatial structure and variability

The genetic population structure of Rigid Apple Moss in Canada has not been studied. The species occurs at the northern edge of its North American geographic range in British Columbia. Subpopulations are generally structured as scattered colonies within suitable habitat patches; these subpopulations are themselves scattered throughout the species’ range.

Designatable units

There is one designatable unit for Rigid Apple Moss in Canada. It is known from only the COSEWIC Pacific National Ecological Area and all subpopulations are in similar habitat with no apparent major dispersal barriers. Therefore, it is unlikely that there are significant differences among subpopulations in Canada.

Special significance

Rigid Apple Moss reaches the northern extent of its North American range in British Columbia. In Canada, Rigid Apple Moss is a rare species that occurs in Garry Oak ecosystems, an exceptional ecosystem type that is also at the northern extent of its range.

Distribution

Global range

Bartramia aprica (Rigid Apple Moss) occurs in the Mediterranean regions of the Northern Hemisphere, including southern parts of Europe and Northern Africa (Damayanti et al. 2012), and the west coast of North America. In North America, it has been documented in southwestern British Columbia, and in Washington and California (Figure 2). Only one Washington occurrence lies between the British Columbia population and California, which is its centre of distribution. In California, the species is known from northern California and the foothills of the Sierra Nevada (eastern California), but is infrequent in both regions.

Figure 2. North American distribution of Rigid Apple Moss. Data from Consortium of Bryophyte Herbaria (2023). American records result from searching for Bartramia stricta and B. aprica. Canadian data are from this report.

Canadian range

In Canada, Rigid Apple Moss is known from twelve extant subpopulations, which are restricted to a small area of southwestern British Columbia (Vancouver Island and adjacent Gulf Islands), all within the Coastal Douglas-fir (CDF) Biogeoclimatic Zone (Figure 3; Table 1; Nuszdorfer et al. 1991). An additional subpopulation on Hornby Island has been recently reported on iNaturalist, but this record has not been verified (iNaturalist 2023). In the 10 years since the previous update report (COSEWIC 2009), rare plant surveys and incidental reports have resulted in the discovery of seven previously unknown Rigid Apple Moss subpopulations (Fairbarns 2008b; Maslovat and Matthias 2017; SSIC 2018; Batten pers. comm. 2018; Table 1).

Figure 3. Canadian distribution of Rigid Apple Moss. Vancouver Island: Mount Finlayson (FIN), Government House (GOH), Mary Hill (MRH), Notch Hill, near Nanoose (NOH), Observatory Hill (OBS); Saltspring Island: Mount Maxwell (MAX), Musgrave Rock (MUR), Reginald Hill (REH), Mount Tuam (TUA); Lasqueti Island: British Columbia Ecological Reserve (LAS); Pender Island: Oaks Bluff (OAB); Sidney Island: Wymond Point (SID), Hornby Island (HOR).

Subpopulations are defined, for COSEWIC assessment purposes, as distinct groups between which there is little demographic or genetic exchange (typically one successful migrant individual or gamete per year or less) (IUCN 2022). Accordingly, Rigid Apple Moss subpopulations are recognized as being distinct when they are separated by more than 1 km, the minimum separation distance that is generally accepted for differentiating subpopulations of many plant species (NatureServe 2020).

Extent of occurrence and area of occupancy

It was not possible to confirm all subpopulations in the field for this report, leading to some uncertainty in the extent of occurrence (EOO) and index of area of occupancy (IAO). Based on known extant subpopulations, the EOO for the species is 2,980 km², and the IAO (based on a 2 x 2 km grid) is 52 km².

COSEWIC (2009) previously reported an EOO of 2,070 km² and an IAO of 28 km². The expansion of the known range of Rigid Apple Moss since the last report represents the discovery of previously unknown subpopulations as a result of increased search effort motivated by the species’ SARA listing.

Search effort

Southwestern British Columbia has been the focus of bryological exploration since the early 1960s, and there have been many collections of mosses made in this area since then.

The previous COSEWIC assessment of Rigid Apple Moss increased the awareness of this species and resulted in additional search effort for it (Table 2). However, surveys in more than 25 areas with apparently suitable habitat have not revealed any new subpopulations of Rigid Apple Moss (McIntosh 2007; Sadler 2007; COSEWIC 2009; Stewart 2018b; Table 3). It remains difficult to quantify the total search effort for the species, given that searches that failed to find the species are not often reported. However, casual observations by professional and amateur botanists likely add substantial undocumented search effort and, given the intense survey effort for bryophytes in the limited area of Garry Oak ecosystems on Vancouver Island and the adjacent Gulf Islands, it is unlikely that a large number of additional subpopulations remain to be found.

Habitat

Habitat requirements

In Canada, Rigid Apple Moss is confined to southwestern British Columbia, particularly to Garry Oak ecosystems that occur within the most xeric portion of the Coastal Douglas-fir (CDF) Biogeoclimatic Zone (Nuszdorfer et al. 1991). The climate in this zone is heavily influenced by the rain shadow created by the Vancouver Island Ranges and the Olympic Mountains and is characterized by warm, dry summers and mild, wet winters. Rigid Apple Moss habitat is confined to habitats characterized as open grasslands with shallow soil (Figure 4 a,b), with scattered Garry Oak (Quercus garryana), Arbutus (Arbutus menziesii), and Douglas-fir (Pseudotsuga menziesii). The habitats in which it occurs are moderately to steeply sloping, often with a south-facing aspect, and are generally below 300 m in elevation.

Figure 4. Examples of habitat for two Rigid Apple Moss subpopulations in Canada: (a) Wymond Point (Sidney Island), and (b) Mary Hill (Vancouver Island). Photos by K. Sadler, 2008.

Within these habitats, Rigid Apple Moss occurs in microsites that are naturally discontinuous and scattered across the landscape. Shade is generally minimal, indirect, or absent (for example, sunlight may be filtered by shrubs growing in proximity or a nearby tree).

Rigid Apple Moss grows in two distinct microhabitats in British Columbia (Figures 5 and 6a,b; Fairbarns 2008c; McIntosh 2009a,b): (1) well-drained, shallow soil that typically appears to be compacted or disturbed, overlying bedrock, where Rigid Apple Moss often occurs in, or close to, intermittently or seasonally moist outflow, and (2) crevices or undersides of small overhangs of meta-igneous rock outcrop faces. Here, it is common to find Rigid Apple Moss on rock faces above seepage. In both microsites, Rigid Apple Moss may be dormant (but still visible) for several months during the summer/early fall drought when seepage flows cease.

Figure 5. Example of Rigid Apple Moss microhabitat: near base of rock outcrop, associated with local drainage. Circled areas above blue site markers indicate two Rigid Apple Moss colonies. Photo by K. Sadler, 2008

Figure 6. Examples of Rigid Apple Moss, growing (a) on shallow soil (from McIntosh 2008, used with permission), and (b) in crevices and under small overhangs, on rock surfaces (photo by K. Sadler, 2008).

Rigid Apple Moss does not co-occur with grasses and herbs. Field observations for status report updates and monitoring purposes have noted that, by eating and trampling vascular plants, abundant native herbivores (for example, feral deer) may sustain or create the microhabitats required by Rigid Apple Moss: compacted, bare, thin soils, and open landscapes with low to moderate shrub encroachment. All of the subpopulations in British Columbia are associated with a moderate to high abundance of herbivores and, while no studies have investigated their effect on Rigid Apple Moss microhabitats specifically, herbivores are known to play a significant role in determining vegetation structure in Garry Oak ecosystems (Martin et al. 2011).

Plants associated with Rigid Apple Moss habitat in Canada are characterized by scattered (non-dominant) patches of invasive grasses in genera such as Vulpia, Anthoxanthum, Cynosurus, Bromus, and Aira. Rigid Apple Moss colonies are often “edged” with patches of Selaginella. Vascular plant associates include Mimulus guttatus, Micranthes integrifolia, Opuntia fragilis, Sedum spathulifolium, and Pentagramma triangularis. The species has also been observed growing near or intermingled with other mosses, including Grimmia trichophylla, Racomitrium heterostichum, Bryum capillare, Polytrichum juniperinum, P. piliferum, and Didymodon vinealis in drier microhabitats, and Bryum miniatum and Scleropodium touretii in seepage pathways.

Habitat trends

Rigid Apple Moss is strongly associated with Garry Oak ecosystems, which are themselves considered “Critically Imperiled” (Erickson 2008; British Columbia CDC 2018). Lea (2006, in GOERT 2019) estimated that, when Europeans first colonized southern Vancouver Island around 1800, Garry Oak ecosystems covered approximately 15,000 ha of the landscape, but by the year 2000, they accounted for just over 1,600 ha, a 91% decline. However, these declines are closer to 66% when considering only the shallow-soil variant of Garry Oak ecosystems, which is the preferred habitat of Rigid Apple Moss (Lea 2006 in GOERT 2019). Regional districts in the core range of Rigid Apple Moss have seen a greater than 23% increase in the human population between 2001 and 2018 (B.C. Stats 2019), an increase that continues to drive further loss of potential habitat to development. While Rigid Apple Moss habitat is naturally patchy across the landscape, urban development further decreases habitat patch sizes and increases distance between patches.

Overall, there is strong paleo-ecological and climate modelling evidence that the Coastal Douglas-fir Biogeoclimatic Zone and Garry Oak and associated ecosystems will expand under predicted climate scenarios (Pellat et al. 2001; Walker and Pellat 2003; Hamann and Wang 2006; Wilson and Hebda 2008, Bodtker et al. 2009; Pellatt and Gedalof 2014; Wang et al. 2016). An increase in climate suitability for the ecosystem as a whole does not necessarily mean increased suitability for Rigid Apple Moss, however. While additional potential habitat may be climatically suitable, the plant community in that habitat may not be suitable. Ecosystems do not move as a unit; plant communities break down and reassemble as individual species move. Furthermore, the landscape disturbance regime (for example, fire suppression, herbivory pressure) is not the same as in the past, and non-native species have been introduced (Gayton 2008; Pojar 2010; Pellatt and Gedalof 2014). In addition, the potential increase in climatically suitable area may be offset by rapid increases in urbanization, at the expense of an increase in natural, suitable habitat (see Threats and Limiting factors).

Biology

There is little information about the specific biology and reproductive capacity of Rigid Apple Moss, with the exception of field observations on microhabitat (see Habitat), information recorded on herbarium vouchers, personal communications with contacted authorities, and several unpublished field surveys (see Table 2 for a list of field studies). Most biological information is inferred from a more general knowledge of bryophyte biology.

Life cycle and reproduction

Most mosses reproduce and disperse via spores. Rigid Apple Moss is synoicous, meaning that both male and female reproductive structures occur in the same inflorescence. This facilitates fertilization and the consequent production of sporangia and spores. Rigid Apple Moss appears to produce sporophytes regularly throughout its range in British Columbia (COSEWIC 2009). The generation time is estimated as 11 to 25 years, and three generations are about 50 years, based on the life history characteristics of long-lived bryophyte species (Bergamini et al. 2019). Rigid Apple Moss can also reproduce vegetatively.

Dispersal and migration

The dispersal abilities for this species are unknown. However, for mosses that have been studied, the proportion of released spores that land near the source is high, but drops steeply within a few metres of the parent plant (Miles and Longton 1992; Roads and Longton 2002; Lönnell et al. 2012). At greater distances (more than 100 m), spore deposition from local sources is virtually indistinguishable from the background atmospheric propagule rain, but still results in successful establishment, at least occasionally (Lönnell et al. 2012; Barbé et al. 2016). Dispersal is considered to be limiting for species like Rigid Apple Moss, whose spores (22 to 32 µm) are large enough to hinder their escape from the immediate boundary air layer (During 1979; van Zanten 1978, 1984). Fragments (for example, detached by mechanical disturbance) can act as vegetative propagules, but are much larger and heavier than spores. In sum, local dispersal of Rigid Apple Moss within subpopulations (to form new colonies) seems likely, but dispersal between subpopulations is much less likely.

The distance between neighbouring subpopulations of Rigid Apple Moss in British Columbia is generally less than 25 km, although the two northern subpopulations on Lasqueti Island and Notch Hill are separated by 75 km from the nearest southern subpopulations on Saltspring Island. While some population fragmentation has undoubtedly occurred due to urban development, the Canadian population is not believed to be severely fragmented.

Interspecific interactions

Rigid Apple Moss is not a competitively dominant species. Rigid Apple Moss individuals are often observed growing among other bryophyte taxa and the nature of such associations with other mosses (that is, competitive, facilitative, or neutral) is not known. Encroaching herbs and shrubs alter appropriate habitat qualities and may competitively exclude Rigid Apple Moss by occupying the available space, as it does not co-occur closely with vascular plants.

Population sizes and trends

Sampling effort and methods

The sampling effort for the species is estimated to be >1,250 hours between 1997 and 2018 (Table 2). While personnel and survey methods have varied, the general methodology used in surveys has involved locating suitable habitat based on known habitat features and closely examining rock faces and soil at the base of bedrock outcrops to locate the species. In some cases, transects were used (for example, Sadler 2009), but in most surveys, potential habitat was located by air photo interpretation, visual surveys, and proximity to known colonies. Suitable habitat searched included open grasslands with shallow soil and rock outcrop landscapes where the species’ preferred substrates (rock crevices, overhangs, and thin-soiled flats close to rock bases) were present. When Rigid Apple Moss was observed, notes were taken to describe the surrounding landscape (for example, aspect, slope, canopy cover, GPS coordinates) and individual colonies (for example, number, area, substrate characteristics, associated species). Photographs were taken to document pertinent landscape features and Rigid Apple Moss colony size and shape. It should be noted that, for some subpopulations, the potential habitats are expansive and could not be exhaustively surveyed in the allotted time (for example, >18 ha at Sidney Island with seven hours and three surveyors in 2018). More detailed surveys may reveal additional individuals in these subpopulations.

Abundance

For the purposes of this status report, a mature individual is defined as a single colony, as per Bergamini et al. (2019). Targeted surveys of subpopulations reported in the previous status report (COSEWIC 2009) and the discovery of new subpopulations have increased the documented abundance of Rigid Apple Moss in British Columbia from 667 individuals to 1,136 individuals (COSEWIC 2009; Table 4). Owing to the difficulties of determining the area “covered” by an individual colony, a measure reported by several authors (for example, McIntosh and Joya 2018a,b)—the area “abundance”—is not included in this report. Such difficulties include small, scattered colonies; complex and sometimes steep landscape; seasonal changes in the area covered by the moss in hydrated versus desiccated states; the complex shape of colonies; and differences among observers and survey methods.

Fluctuations and trends

Trends in the number and distribution of Rigid Apple Moss colonies within and among subpopulations are difficult to estimate for various reasons. In addition to the difficulties of characterizing abundance (see above), monitoring methods were not effective in determining whether newly observed colonies were recently established or simply missed during prior surveys (McIntosh and Joya 2018a,b). Regular long-term monitoring has not occurred for most subpopulations, and where more than one survey was undertaken for a subpopulation, inconsistencies among observers and the seasonal variability of surveys have introduced uncertainty in the interpretation of population trends. Rather than an actual increase in range, the increase in known range of Rigid Apple Moss since the last report represents the new discovery of pre-existing subpopulations, as a result of increased search effort inspired by the species’ SARA listing. For these reasons (and those below), population trends are largely unknown. Nevertheless, while historical data are limited, historical decline can be inferred from a documented decline in Garry Oak ecosystems (Lea 2006 in GOERT 2019).

Mary Hill, Notch Hill, and Lasqueti Island are large subpopulations, accounting for much of the known population (>68% of individuals). As previously noted, the increase in the number of known colonies is likely a result of increased search effort as opposed to an increase in population size (Belland 1997; Byrne et. al 2005; Fairbarns 2008a; McIntosh 2009; McIntosh and Sadler 2011b; McIntosh and Joya 2018a,b; Stewart 2018). McIntosh and Joya (2018a,b) and Stewart (2018) compared data collected in 2008 with 2018 surveys and, while several limitations were identified, they determined that all three subpopulations were at least stable and in good health.

Observatory Hill has been relatively well studied on an annual basis: following Sadler’s 2009 survey, multi-year monitoring was implemented and detected little change (Sadler 2011; McIntosh 2012; McIntosh and Miles 2013; Miles 2015, 2016, 2017). However, Miles (2017) noted that invasive plants (Scotch Broom, or Cytisus scoparius, seedlings and grasses) had been removed from colonies during monitoring and that invasive grass and herb abundance may be increasing. In 2018, surveys for the present status report noted that two of the three groups of colonies appeared to be in poor health. Based on these reports, it appears that this subpopulation is declining in both numbers and health of colonies (Miles 2017).

Sidney Island has seen some residential development (Sadler 2007); however, the Rigid Apple Moss colonies are protected within covenanted areas. During field work for this status report, most of Sadler’s (2010) colonies were visited and the Rigid Apple Moss colonies that were present were healthy; however, some colonies could not be located and may have been overtaken by grasses.

The subpopulations at Government House and on Mount Finlayson, Saltspring Island, and Pender Island (where the subpopulation could not be confirmed for this report) have not been monitored, and therefore trends cannot be determined. However, the habitat has not been developed and most colonies are located within protected areas.

One subpopulation is believed to be extirpated (Ash Point). This subpopulation is close to the Mary Hill subpopulation and was reported in 1996 (Ryan 1996). The Ash Point (Pedder Bay) voucher specimen has been confirmed (COSEWIC 2009). However, searches by Belland (1997) and others in 2008 (McIntosh pers. comm. 2008) did not relocate Rigid Apple Moss at Ash Point, which was noted at the time to have large amounts of Scotch Broom. The Ash Point site was not searched in preparation for this status update. According to the best available information, the subpopulation is currently presumed to have been extirpated due to the ingrowth of invasive vascular vegetation (British Columbia CDC 2018).

There is no evidence from 20 years of observations of the species in Canada or from the published literature that the species shows extreme fluctuations in numbers of individuals. Mosses in this genus do not normally exhibit these fluctuations.

Rescue effect

The migration of Rigid Apple Moss propagules between Canada and the United States is unlikely (see Dispersal and migration). The nearest potential source for rescue is in Washington, over 300 km away, in a direction that is not aligned with the prevailing winds. The possibility that undiscovered subpopulations are present in the intervening areas is low, as only a small amount of suitable habitat for Rigid Apple Moss exists in Washington (J. Harpel pers. comm. 2009). The nearby San Juan Islands (in northwestern Washington), which have similar habitats to those of the British Columbian subpopulations, have been extensively surveyed and Rigid Apple Moss was not recorded (Harpel 1997). The next nearest population, in California, is over 800 km away.

Threats and limiting factors

Ecosystem conversion, or the direct and complete conversion of natural landscapes to developed ones, is one of the greatest stresses on biodiversity in British Columbia (Long 2007). Conversion reduces or eliminates the ability of native species to survive in new conditions, forcing them to adapt, migrate, or die (Austin et al. 2008), and diminishes habitat qualities that buffer or mitigate the suddenness of the change. A large portion of the Coastal Douglas-fir (CDF) Biogeoclimatic Zone of southeastern Vancouver Island has been converted to urban and agricultural uses (Austin et al. 2008). The extent of Garry Oak ecosystems in British Columbia has been reduced by 91% since European colonization, and it seems likely that many subpopulations of Rigid Apple Moss have also been lost.

Within the context of degradation and fragmentation of the ecosystems in which Rigid Apple Moss occurs, global climate change is also rapidly accelerating. Climate projections for southwestern British Columbia by the Pacific Climate Impacts Consortium (PCIC) indicate that the impacts of climate change in southwestern British Columbia will include higher temperatures, prolonged droughts, and an increased frequency of severe weather events within the next 30 years (CRD 2017). The persistence of some bryophyte species at risk will be threatened by climate change and associated threats, such as the increased frequency and severity of fires and competition from invasive species. It seems unlikely that habitat specialists like Rigid Apple Moss, which relies on increasingly small, degraded, and fragmented Garry Oak ecosystems in British Columbia, will be able to migrate or adapt to the novel ecosystems of the future.

The threats to Rigid Apple moss were assessed based on the IUCN-CMP (World Conservation Union–Conservation Measures Partnership) unified threats classification system (IUCN and CMP 2006; Salafsky et al. 2008; Master et al. 2009). They are discussed below in decreasing order of impact, ending with those for which the impact is unknown (see Appendix 1 for details). The overall threat impact assigned to Rigid Apple Moss is “Very high” (Appendix 1).

Threats

Climate change and severe weather (threat category 11.0) - high

Climate models for southwestern British Columbia project higher temperatures and increasingly frequent severe weather events over the next 30 years. Garry Oak ecosystems, like others that are already stressed by extensive disturbances, will have low resilience as these changes take place (Austin et al. 2008).

The climate of British Columbia was relatively stable for approximately 4,000 years, shaping the composition and distribution of current ecosystems in the southern part of the province (Hebda 1997; Brown and Hebda 2002). Increasing atmospheric greenhouse gas emissions are expected to soon exceed the biological tolerances of many species, compromising the resilience of many ecosystems (Hebda 1997; Hanann and Wong 2006; Austin et al. 2008).

The rate of climate change in southwestern British Columbia has alarmed local governments and organizations to the point where Metro Vancouver (2016), the Capital Regional District (2017), the City of Vancouver (2018), and the British Columbia Agriculture and Food Climate Action Initiative (2020) have turned to the PCIC for climate projection data and have developed and are implementing climate mitigation and adaptation strategies.

In the IUCN Threats Calculator, the overall impact of the threat of Climate Change and Severe Weather was determined to be High, based on the Pervasive scope (71 to 100%), Serious severity (31 to 70%), and High timing (Continuing).

Climate change vulnerability index (appendix 2)

The Climate Change Vulnerability Index (CCVI) was calculated for Rigid Apple Moss to support the climate change appraisal in the Threats Assessment. The vulnerability of Rigid Apple Moss was evaluated using the Canadian version of the CCVI (NatureServe 2022). The CCVI combines information on three components to determine vulnerability: (1) indirect exposure to climate change; (2) species-specific sensitivity and adaptive capacity (including dispersal ability, temperature and precipitation sensitivity, physical habitat specificity, interspecific interactions, and genetic factors); and (3) the adaptive capacity of the species to withstand environmental changes. Indirect exposure to climate change is measured by examining the projected changes in the annual climate moisture deficit across the range of the species within the assessment area, in addition to projected changes in mean annual temperature. The result is a numerical sum for the species. The sum is then converted to a categorical score by comparing it to threshold values (Young and Hammerson 2016). The six possible scores in the CCVI are Extremely Vulnerable, Highly Vulnerable, Moderately Vulnerable, Less Vulnerable, and Insufficient Evidence.

The climate data used is derived from the Intergovernmental Panel on Climate Change’s Fifth Assessment Report (IPCC 2013).

The CCVI calculations resulted in a score of Extremely Vulnerable for Rigid Apple Moss, where the abundance and/or range extent of the species in Canada is extremely likely to substantially decrease or disappear by 2050. This date falls within three generations of the species, using 11 years as the generation time. The confidence in this score was Extremely High.

Habitat shifting and alteration (threat category 11.1)

The extent of the entire Coastal Douglas-fir (CDF) Biogeoclimatic Zone is approximately 1,310 km². It is the smallest biogeoclimatic zone in British Columbia, but it has the largest number of species of global and provincial conservation concern (British Columbia CDC 2021). All four of the Garry Oak ecosystems in British Columbia are provincially and globally endangered (British Columbia CDC 2021); approximately 95% of Garry Oak ecosystems in British Columbia by area have been eliminated or severely degraded by urban or rural development or conversion to agricultural uses. For dispersal-limited, habitat-specialist taxa that occur in small populations (Fischlin et al. 2007) such as Rigid Apple Moss, habitat fragmentation and degradation increase their vulnerability to climate change by reducing the habitat available for migration and the chance of successful dispersal to suitable habitat patches (Austin et al. 2008).

Habitat shifting and alteration can be expected to have dire consequences for narrow habitat specialists with limited dispersal capacities like Rigid Apple Moss. As climate change proceeds and species reassemble to form novel ecosystems, some species will thrive, while others will decline. Extreme events linked to climate change, such as prolonged drought and wildfires, will rapidly and dramatically affect the structure, composition and function of some ecosystems in southwestern British Columbia, and will be layered over more general, gradual climate change. In this dynamic context, invasive species adapted to drought-stressed, disturbed landscapes are likely to outcompete more slowly growing, dispersal-limited and competition-averse native plants (Metro Vancouver 2016) such as Rigid Apple Moss.

Owing to the predicted impacts on the structure and composition of Garry Oak ecosystems in southwestern British Columbia and the limited potential for Rigid Apple Moss to adapt or disperse to the novel ecosystems that are expected to arise within the next 30 years, the scope of the Habitat Shifting and Alteration threat was scored as Pervasive (71 to 100%), the severity as Serious (31 to 70%), and the timing as High (Continuing) in the IUCN Threats Calculator. The overall impact of the threat is High.

Droughts (threat category 11.2)

The Mediterranean-like climate of the Coastal Douglas-fir (CDF) Biogeoclimatic Zone is caused by the rain-shadow effect of the nearby mountains. By 2050, summer precipitation in this zone is projected to decrease by 19% and droughts are projected to increase in duration by 23%, from 23 to 29 consecutive dry days on average, per year (British Columbia Agriculture and Food Climate Action Initiative 2020).

The drought tolerance of Rigid Apple Moss has not been quantified, but some inferences may be drawn from its macro- and micro-habitat affiliations. It is associated with seeps (see Habitat), a microhabitat that is vulnerable to changes in size and duration or constancy during drought scenarios. The sources of seeps that have been assessed in connection with critical habitat delineation are small (Parks Canada Agency unpubl. data 2011). Furthermore, the California range of the Rigid Apple Moss species that occurs in British Columbia (Bartramia cf. rosamrosiae) is restricted to the Sierra Nevada foothills and northern California (Neumann et al. 2019), where the length of the rain-free season is much shorter and summers are cooler (see Temperature Extremes threat) than in the coastal mountain ranges occupied by the much more common Bartramia aprica. These observations indicate that Bartramia cf. rosamrosiae is likely less desiccation tolerant than B. aprica, and may not withstand long periods of drought.

In the IUCN Threats Calculator, the scope of the Droughts threat was scored as Pervasive (71 to 100%), the severity as Serious (31 to 70%), and the timing as High (Ongoing). The overall impact of the threat was rated as High.

Temperature extremes (threat category 11.3)

Summer temperatures on southeastern Vancouver Island and the adjacent Gulf Islands are increasing. By the 2050s, summer daytime high temperatures are projected to increase by 3.3 °C, and by more than 5 °C by 2080 (CRD 2017), while maximum summer temperatures are projected to be 3 °C warmer by 2050. Climate models project that the number of days exceeding 25 °C will triple from a baseline of 11 per year to 33, and the number of days exceeding 30 °C will increase sixfold from a baseline of one per year to six by 2050 (CRD 2017; British Columbia Agriculture and Food Climate Action Initiative 2020).

Temperatures on extremely hot days (1-in-20-year events) previously reached 32 °C in the region. By the 2050s, they are projected to reach 36 °C, a 12% increase, and by the 2080s, 37 °C (CRD 2017). However, these thresholds had already been exceeded by 2021 (see, for instance, Environment and Natural Resources 2023).

The tolerance of Rigid Apple Moss to temperature extremes has not been studied. However, increased evapotranspiration, particularly in combination with reduced moisture, is expected to increase periods of moss inactivity during which no growth or reproduction are possible. The species’ California range is cooler than that of Bartramia aprica, which is frequently found in the hotter mountains west of San Joaquin Valley; this suggests the former’s more limited tolerance of high temperatures and presumably, drought. In the IUCN Threats Calculator, the scope of the Temperature Extremes threat was scored as Pervasive (71 to 100%); the severity as Serious–Slight (1 to 70%) to reflect the uncertainty of the impact of this threat; and the timing as High (Ongoing).

Storms and flooding (threat category 11.4)

By 2050, precipitation is projected to increase by approximately 5% annually in the areas where Rigid Apple Moss occurs, but it will not be evenly distributed throughout the year. Winter will continue to be the wettest season, but rainfall will increase by 7% in spring and 12% in fall. Precipitation on very wet days (exceeding the baseline 95th percentile threshold) is projected to produce approximately 31% more rain by the 2050s and 59% more rain by the 2080s. Extreme rainfall events (the 99th percentile wettest days) are expected to be increasingly common and intense. Precipitation events are projected to increase by 68% by the 2050s, and 126% by the 2080s (CRD 2017), greatly increasing the potential for flooding (PCIC 2016; British Columbia Agriculture and Food Climate Action Initiative 2020).

All subpopulations of Rigid Apple Moss will be subject to the threat from storms within the next 30 years. Heavy rain will increase the short-term flow of water over slopes where colonies occur on shallow soils. However, this soil is well drained and will quickly absorb water following the long period of summer drought. It is unlikely that colonies on outcrops will be affected by erosion or flooding. Therefore, the impact of the Storms and Flooding threat was scored as Negligible in the IUCN Threats Calculator (Appendix 1).

Natural system modifications (threat category 7.0) - high

Fire and fire suppression (threat category 7.1)

The projected longer, warmer, and drier summers will increase the length of the fire season and the frequency and severity of wildfire events (Austin et al. 2008; Metro Vancouver 2016; Kirchmeier-Young et al. 2019; British Columbia Agriculture and Food Climate Action Initiative 2020). At the time of European settlement, fires were relatively common throughout the Coastal Douglas-fir (CDF) Biogeoclimatic Zone. Sparsely treed Garry Oak ecosystems, including meadows, prairies, and savannahs, were maintained by Indigenous peoples who deliberately set fires to enhance growing conditions for important food crops like camas, to improve forage for game species and thus facilitate hunting, and to ease travel across the landscape (Agee 1993; Pellatt et al. 2001, 2007; MacDougall et al. 2004; Anderson 2007; Dunwiddie et al. 2011; McCune et al. 2013; Pellatt and Gedalof 2014). There were also natural fires.

This traditional land management shaped the composition and structure of Garry Oak plant communities (Tveten and Fonda 1999; Thysell and Carey 2001). Cessation of Indigenous burning coincided with increased dominance of Douglas-fir rather than Garry Oak and a major influx of non-native species, resulting in decreased richness and abundance of native plants. Although it has been suggested that prescribed burning could function as an alternative to natural fire regimes and traditional land management, the invasive plants that dominate contemporary Garry Oak ecosystems are favoured by disturbance (Agee 1993; Grace et al. 2001) and are known to alter ecosystem properties by nitrogen fixation and other ecosystem processes. Furthermore, the large monetary costs and risks of reintroducing fires to patchily distributed remnant Garry Oak ecosystems within the developed landscape make the widespread application of prescribed burning untenable (see MacDougall and Turkington 2006, 2007).

The threat of severe and frequent wildfires by 2050 is high, particularly because fire suppression has led to high fuel loads and, during this time frame, the moss may already be stressed by high temperatures and drought.

It is unlikely that all subpopulations of Rigid Apple Moss would be equally vulnerable to wildfire, particularly because some of the subpopulations are found on rocky sites with lower fuel loads. However, in the IUCN Threats Calculator, the scope of the combined threats of fire and fire suppression was scored as Large (31 to 70%), the severity as Extreme (71 to 100%), and the timing as Moderate (possibly in the short term, <10 years / 3 generations, whichever is longer), for an overall impact of High.

Invasive and other problematic species and genes (threat category 8.0) - high

Invasive non-native species (threat category 8.1)

More than 100 threatened or endangered species associated with Garry Oak ecosystems (GOERT 2011), including Rigid Apple Moss, are vulnerable to being outcompeted by invasive species such as Scotch Broom, Himalayan Blackberry (Rubus armeniacus), numerous non-native grasses, and other herbaceous plants (Austin et al. 2008). Cessation of natural disturbance regimes, pervasive human activity that fragments and degrades habitats, and changes in temperature and precipitation such as those projected for the region (Metro Vancouver 2016; British Columbia Agriculture and Food Climate Action Initiative 2020) promote invasive species.

Rigid Apple Moss colonies occurring on shallow, well-drained, compacted or disturbed soils will likely be more vulnerable to the threat of invasive species than colonies associated with bedrock habitats, which are less hospitable to vascular plants.

In the IUCN Threats Assessment, the scope of the invasive non-native species threat was assessed as Large (30 to 70%), the severity as Serious (31 to 70%), and the timing as High (Continuing), for an overall impact of High.

Residential and commercial development (threat category 1.0) - low

Housing and urban areas (threat category 1.1)

Most extant subpopulations of Rigid Apple Moss are found on federal land or in parks, nature reserves, and covenanted areas. Therefore, the current overall impact of the threat from Housing and Urban Areas on the species is considered to be low. Critical habitat has not been identified for all subpopulations, but where it has been identified, drainages supplying seepage are small and generally contained within a single property (Parks Canada Agency unpubl. data 2011). There are no known plans to develop housing on private property where critical habitat has been identified.

In the IUCN Threats Calculator, the overall impact of the Housing and Urban Areas threat was determined to be Low. The scope was scored as Small (1 to 10%), based on two known subpopulations potentially being vulnerable to the threat. Severity was rated Serious (31 to 70%), and timing, Moderate (possibly in the short term, <10 years / 3 generations, whichever is longer).

While the overall impact of the threat from urbanization is deemed to be Low, human population growth within the range of Rigid Apple Moss has been rapid in recent years. For instance, Victoria’s population grew by 8% in the five years from 2016 to 2021 (Langford tops population growth in B.C., third-fastest in Canada: 2021 census), as did the populations of Nanaimo and Courtenay (Nanaimo/Courtenay found to have highest population growth on the island; Statscan). Overall, population growth on Vancouver Island is expected to increase by more than 101,000 people from 2020 to 2040 (PEOPLE 2020: BC Sub-Provincial Population Projections). Given these increases, it is expected that urbanization will increase concomitantly.

Human intrusions and disturbance (threat category 6.0) - low

Recreational activities (threat category 6.1)

All known subpopulations of Rigid Apple Moss are exposed to the threat of human intrusion and disturbance to varying degrees. Colonies occurring on rocky outcrops are less exposed to trampling than colonies located on soil. No known colonies are located immediately adjacent to trails or other areas where they would be subjected to frequent disturbance by recreational activities. However, some colonies on Notch Hill, for example, sustain occasional impacts from hiking and dog walking.

In the IUCN Threats Calculator, the impact of the Recreational Activities threat was determined to be Low, based on the scope being scored as Restricted (11 to 30%), the severity as Moderate (11 to 30%), and the timing as High (Continuing).

War, civil unrest and military exercises (threat category 6.2)

Two of the 13 verified subpopulations of Rigid Apple Moss, including most of the known colonies, are located on Department of National Defence (DND) lands and are protected under SARA. The subpopulations on Notch Hill (Canadian Forces Maritime Experimental Test Ranges, or CFMETR), near Nanoose, and Mary Hill, near Metchosin, both on Vancouver Island, have been inventoried and monitored as detailed in several reports (for example, Byrne et al. 2005; Fairbarns 2008b; McIntosh 2009a,b; McIntosh and Sadler 2011a,b; McIntosh and Joya 2018a,b).

Protection under SARA and detailed knowledge of the locations of the colonies suggest that the overall impact of the threat from military exercises on DND lands is Negligible. In the IUCN Threats Calculator, the scope of the threat was scored as Large (31 to 70%) based on the large number of colonies known from the DND lands compared to other subpopulations, the severity as Negligible (<1%), and the timing as High (Continuing).

Work and other activities (threat category 6.3)

Researchers and conservation practitioners must take care not to negatively impact Rigid Apple Moss by over-collecting the species, or by undertaking restoration activities for Garry Oak ecosystems or for other taxa without considering the unintended effects.

In the IUCN Threats Calculator, the overall impact of Work and Other Activities was determined to be Negligible. This is based on the scope being scored as Pervasive (71 to 100%), because the entire population is subject to the threat; the severity, Negligible (<1%); and the timing, High (Continuing), because it is expected that the moss will be studied in the future and it seems likely that restoration activities will occur at the sites where it is found.

Limiting factors

Habitat/microhabitat specificity and limited dispersal distance are two key factors that may limit the species’ response to recovery or conservation efforts.

Reliance on a narrow range of specific micro- and macro-habitat requirements is the main limiting factor for Rigid Apple Moss. Rigid Apple Moss is particularly sensitive to global climate change, owing to its close association with specific and rare macro- and micro-climatic patterns that are projected to be altered by increasingly severe and frequent temperature and precipitation extremes. This sensitivity is supported by the NatureServe Climate Change Vulnerability Index, which determined that the species was Extremely Vulnerable to climate change, a result that strongly supports the Threats Assessment results for Climate Change and Severe Weather.

The limited dispersal distance of the species hinders its ability to colonize new sites, since threats such as residential and commercial development and human intrusion and disturbance (that is, recreation, military exercises, and work) are more restricted in scope than climate change, or are less imminent. Nevertheless, in recent years, the species’ habitat type has been destroyed and degraded by urban development. Rigid Apple Moss is a temperate (Mediterranean) species and, in Canada, is restricted to Garry Oak ecosystems which are themselves considered “Critically Imperiled” (British Columbia CDC 2018).

Number of locations

The most plausible number of locations is 1 to 13. If based on climate change alone, the number of locations would be one. Despite varying local climate influences such as aspect and elevation, the climate change threat is expected to result in one location. This is because the changes projected by all climate models (for example, high temperatures, drought) are of such a high magnitude that they will likely override these influences, so that all subpopulations will be affected similarly and simultaneously, because they are in the same biogeoclimatic zone and the EOO is relatively small (2,980 km²).

However, the Fire and Fire Suppression and Invasive and Other Problematic Species and Genes threats were also scored High. For instance, severe and frequent wildfires are driven by high temperatures and extended periods of drought; both are factors associated with climate change. Climate change is also predicted to give invasive plants, which are already ubiquitous in Garry Oak ecosystems, a competitive edge over native plants (by 2080, see Invasive non-native species [Threat category 8.1]). Both threats will be exacerbated by climate change and may affect the timing and severity of subpopulation decline. Although smaller subpopulations (<100 colonies) comprise only 32% of all known populations, they account for 9 out of 13 of the extant sites. These smaller subpopulations will be affected in a shorter period of time (1 generation, ~16 to 18 yrs.).

Protection, status and ranks

Legal protection and status

Rigid Apple Moss is listed as Endangered (2003) in Schedule 1 of Canada’s Species at Risk Act (SARA) and therefore is afforded protection on federal lands. The federal recovery strategy for the species was published in June 2011 (Parks Canada Agency 2011). The recovery strategy identifies the species’ critical habitat at Mary Hill, Notch Hill, and Lasqueti Island, but does not take into account the most recently discovered colonies. The following recovery actions are outlined in the recovery strategy: protect extant subpopulations (high priority), research (medium priority), and inventory (low priority). Progress on implementing the recovery actions has been made in all areas through a variety of studies and inventory (Table 1); however, some actions such as identifying additional critical habitat and implementing ongoing, standardized monitoring for all subpopulations remain to be fully implemented. An action plan was scheduled for completion in July 2016, but has not yet been published.

In British Columbia, Rigid Apple Moss is protected by provincial legislation in locations where it occurs on lands managed under the Ecological Reserve Act or the Park Act as of 2017.

Non-legal status and ranks

Rigid Apple Moss (based on the B. stricta name) has been assigned a global rank of GU (unrankable) due to a lack of range information (NatureServe 2023). This uncertainty is increased by recent taxonomic work that found two taxa, with different ranges, within the range that B. stricta was previously understood to occupy. The national rank for Rigid Apple Moss in Canada is N2 (Imperiled). In British Columbia, Rigid Apple Moss is provincially ranked “S2” (2015) by the B.C. Conservation Data Centre (British Columbia CDC 2018). This rank indicates that the species is considered “Imperiled” because of rarity due to “very restricted range, very few populations (often 20 or fewer), steep declines, or other factors making it very vulnerable to extirpation” (NatureServe 2018). Rigid Apple Moss is included on the “Red List” compiled by the British Columbia Ministry of Environment and Climate Change Strategy (MOECCS).

In the United States, Rigid Apple Moss has a national ranking of N1N2 (“Critically Imperiled” to “Imperiled”). It has not been ranked at the state level.

Habitat protection and ownership

Most subpopulations are protected to some extent. Eight of the extant subpopulations have legal protection under a variety of statutes and other legal instruments, including the federal Species at Risk Act (three subpopulations), the provincial Ecological Reserve Act (one subpopulation), and Park Act (two subpopulations), and various environmental covenants (one subpopulation); in addition, one subpopulation is located in a Capital Regional District park (protection unknown) (Table 5). One additional subpopulation is in a privately held nature reserve owned by a conservancy. Of the three remaining subpopulations, two are on publicly owned land with no known legal protection. The final subpopulation is on private land with no known protection, although it occurs off trail in a remote area.

Acknowledgements and authorities contacted

The report writer thanks Kella Sadler for preparing the previous status report that was used as the basis for this update and René Belland for preparing the original status report. The writer acknowledges funding from Environment and Climate Change Canada and support from the COSEWIC Mosses and Lichens Subcommittee and the COSEWIC Secretariat. Further thanks and acknowledgements are in order for the many people who contributed to this report. Dr. Terry McIntosh provided advice, guidance, and specimen identification. Matt Fairbarns shared advice and data, and collaborated in the field. Thanks also to Marta Donovan, who assisted with records from the Conservation Data Centre, and to Olivia Lee and Judy Harpel, who provided information from the University of British Columbia Herbarium and assisted with specimen loans. Shannon Kimball was invaluable in tracking down and facilitating confirmation of a specimen at the University of Montana Herbarium. The writer is grateful to Ryan Batten and Carrina Maslovat for providing information on new subpopulations on Saltspring Island and elsewhere. Thank you to all land owners and managers who provided information and facilitated land access for surveys: Derek Moor, Erica McClaren, Cynthia Vance, Clyde Donnelly, Roy Smitshoek and Dan Polson, Wendy Tyrrell, Nuala Murphy, Kate Emmings, and Christine Torgrimson. Thanks also to Matthew Huntley (ECCC), for providing information on the species, and to Ian Cruickshank and Alanah Nasadyk for providing assistance with the field survey of Sidney Island.

Authorities contacted

Batten, Ryan
Botanist (mosses, lichens and plants)
Victoria, B.C.

Ceska, Adolf
Botanist and Plant Ecologist
Ceska Geobotanical Consulting
Victoria, B.C.

Cornforth, Tracy
Department of National Defence
Victoria, B.C.

Costanzo, Brenda
Vegetation Ecologist
British Columbia Ministry of Environment and Climate Change Strategy
Victoria, B.C.

Davis, Kathryn
Scientific Project Officer and ATK Coordinator
COSEWIC Secretariat
Gatineau, Que.

Fairbarns, Matt
Botanist and Plant Ecologist
Victoria, B.C.

Goggin, Geneviève
A/ Species at Risk Manager
Parks Canada Agency
Vancouver, B.C.

Griffin, Dana G., III
Florida Museum of Natural History
University of Florida
Gainesville, Fla., United States

Huntley, Matt
Species at Risk Biologist
Conservation Planning Unit, CWS
Vancouver, B.C.

Kimball, Shannon
University of Montana Herbarium
Missoula, Mont., United States

Maslovat, Carrina
Botanist and Plant Ecologist
Saltspring Island, B.C.

McCollough, Rayo
Information Manager
Natural Heritage New Mexico
University of New Mexico
Albuquerque, N. Mex., United States

McIntosh, Terry
Bryologist, Recovery Team Member
Vancouver, B. C.

Robinson, Arthur
Federal Lands Forester
Pacific Forestry Centre
Victoria, B.C.

Soares, Rosana Nobre
GIS and Scientific Project Officer
COSEWIC Secretariat
Gatineau, Que.

Wagner, David H.
CEO, Senior Scientist
Northwest Botanical Institute
Eugene, Ore.

Information sources

Agee, J.K. 1993. Fire Ecology of Pacific Northwest Forests. Island Press, Washington, DC.

Anderson, M.K. 2007. Indigenous uses, management, and restoration of oaks of the far western United States. Technical Note #2. USDA United States Department of Agriculture, Natural Resources Conservation Service, National Plant Data Center, Davis, USA.

Austin, M.A., D.A. Buffett, D.J. Nicolson, G.G.E. Scudder, and V. Stevens (eds.). 2008. 2008. Taking Nature’s Pulse: The Status of Biodiversity in British Columbia. Biodiversity BC, Victoria, BC. 268 pp. Website: www.biodiversityBritish Columbia.org [accessed 14 June 2021].

Barbé, M., N.J. Fenton, and Y. Bergeron. 2016. So close and yet so far away: long-distance dispersal events govern bryophyte metacommunity reassembly. Journal of Ecology 104:1707-1719.

Batten, R., pers. comm. 2018. Email correspondence to and in person communication with C. Webb. August–September 2018. Moss, lichen and plant specialist, Victoria, British Columbia.

B.C. Agriculture and Food Climate Action Initiative. 2020. Vancouver Island Adaptation Strategies. British Columbia Agriculture and Food Climate Action Initiative.

B.C. Stats. 2019. British Columbia Development Region, Regional District and Municipal Population Estimates. Website: https://www2.gov.bc.ca/gov/content/data/statistics/people-population-community/population/population-estimates [accessed August 2019].

Belland, R.J. 1997. COSEWIC status report on the rigid apple moss Bartramia stricta in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 124 pp.

Bergamini, A., I. Bisang, N. Hodgetts, N. Lockhart, J. van Rooy, and T. Hallingbäck. 2019. Recommendations for the use of critical terms when applying IUCN red-listing criteria to bryophytes. Lindbergia 42(1):1-6. https://doi.org/10.25227/linbg.01117.

British Columbia Conservation Data Centre (British Columbia CDC). 2018. British Columbia Species and Ecosystems Explorer. British Columbia Ministry of Environ. Victoria, British Columbia. Website: http://a100.gov.British Columbia.ca/pub/eswp/ [accessed August 2018].

Brown, K.J., and R.J. Hebda. 2002. Origin, development, and dynamics of coastal temperate conifer rainforests of southern Vancouver Island, Canada. Canadian Journal of Forest Research 32:353-372.

Byrne, L., N. Ayotte, and A. Robinson. 2005. Survey for Rigid Apple Moss (Bartramia stricta) on Department of National Defense Land on Vancouver Island (CFMETR and Mary Hill). DND/CFS Natural Resources Program, IRF Project #397. Natural Resources Canada and Canadian Forest Service, Victoria, British Columbia. vi + 11 pp.

City of Vancouver Sustainability Group. 2018. Climate change adaptation strategy: 2018 update and action plan. City of Vancouver, Vancouver, British Columbia. 62 pp.

Consortium of Bryophyte Herbaria. 2023. Website: https://bryophyteportal.org/portal [accessed Dec 13, 2023].

COSEWIC. 2009. COSEWIC assessment and status report on the Rigid Apple Moss Bartramia stricta in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. x + 29 pp. Website: https://wildlife-species.Canada.ca/species-risk-registry/document/default_e.cfm?documentID=2053.

CRD. 2017. Climate projections for the Capital Region. Capital Regional District, Victoria, British Columbia. 44 pp. + appendix. Website: https://www.crd.bc.ca/docs/default-source/climate-action-pdf/reports/2017-07-17_climateprojectionsforthecapitalregion_final.pdf [accessed June 14, 2021].

Damayanti, L., J. Muñoz, S. Wicke, L. Symmank, B. Shaw, J. Frahm, and D. Quandt. 2012. Common but new: Bartramia rosamrosiae, a “new” widespread species of apple mosses (Bartramiales, Bryophytina) from the Mediterranean and western North America. Phytotaxa 73:37-59.

Dunwiddie, P.W., J.D. Bakker, M. Almaguer-Bay, and C.B. Sprenger. 2011. Environmental history of a Garry Oak/Douglas-fir woodland on Waldron Island, Washington. Northwest Science 85(2):130-140. https://doi.org/10.3955/046.085.0205.

During, H.J. 1979. Life history strategies of bryophytes: a preliminary review. Lindbergia 5:2-18.

Environment and Natural Resources. 2023. Hourly Data Report for June 28, 2021 for Victoria Gonzales CS, BC.

Erickson, W.R. 2008. Results and data from an ecological study of Garry Oak (Quercus garryana) ecosystems in Southwestern British Columbia. Technical Report 043. Ministry of Forests and Range, Forest Science Program. Victoria, British Columbia. viii + 61 pp.

Fairbarns, M. 2008a. Survey for Meconella oregana (White Meconella), Canadian Forces Maritime Experimental and Testing Ranges (CFMETR), April–June 2007. Natural Resources Canada, Victoria, British Columbia. 17 pp.

Fairbarns, M. 2008b. Bartramia stricta (Rigid Apple Moss) on Observatory Hill, British Columbia. Field Survey Form (Plants), submitted to British Columbia Conservation Data Centre, Victoria, British Columbia.

Fairbarns, M. 2008c. Report on Potential Critical Habitat in Garry Oak Ecosystems. Aruncus Consulting, unpublished report prepared for the Ecosystems Branch, BC Ministry of Environment (funded by the Interdepartmental Recovery Fund and the Government of BC). Victoria, BC. 220 pp.

Fairbarns, M. 2013. Monitoring Report: Islands Trust Rare Plant Baseline Monitoring. Islands Trust, Victoria, British Columbia. 23 pp.

Fairbarns, M. 2014. Fine Scale Habitat Mapping for Observatory Hill. Prepared for National Research Council Canada. Victoria, British Columbia. 65 pp.

Fairbarns, M., pers. comm. 2018. Email communication to C. Webb. September 2018. Botanist and plant ecologist. Victoria, British Columbia.

Fischlin, A., G.F. Midgely, J.T. Price, R. Leemans, B. Gopal, C. Turley, M.D.A. Rounsevell, O.P. Dube, J. Tarazona, and A.A. Velichko. 2007. Ecosystems, their properties, goods and services. Pp. 211-272 in M.L. Parry, O.F. Canziani, J.P. Palutikof, P. van der Linden, and C. Hanson (eds.). Climate Change 2007: Impacts, Adaptation and Vulnerability, Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, UK.

Flora of North America Association: Bartramia stricta illustration by P.M. Eckel, 2004; used with permission (approved December, 2008). Missouri Botanical Garden.

Garry Oak Ecosystems Recovery Team (GOERT). 2019. What Remains of Garry Oak Ecosystems? Website: https://goert.ca/about/what-remains/ [accessed June 2022].

GOERT (Garry Oak Ecosystems Recovery Team). 2011. Restoring British Columbia’s Garry Oak ecosystems: principles and practices.

Gonzales, E.K., and P. Arcese. 2008. Herbivory more limiting than competition on early and established native plants in an invaded meadow. Ecology 89:3282-3289. doi: https://doi.org/10.1890/08-0435.1.

Gonzales, E.K., and D.R. Clements. 2010. Plant community biomass shifts in response to mowing and fencing in invaded oak meadows with non-native grasses and abundant ungulates. Restoration Ecology 18:753-761. doi: https://doi.org/10.1111/j.1526-100X.2009.00535.x

Grace, J.B., M.D. Smith, S.L. Grace, S.L. Collins, and T.J. Stohlgren. 2001. Interactions between fire and invasive plants in temperate grasslands of North America. Pp. 40-65, in K.E.M. Galley and T.P. Wilson (eds.). Proceedings of the Invasive Species Workshop: The Role of Fire in the Control and Spread of Invasive Species, Fire Conference 2000: The First National Congress on Fire Ecology, Prevention, and Management, Tall Timbers Research Station, Tallahassee, FL.

Griffin, D. 2014. Bartramiaceae. Pp. 101, 103. in Flora of North America Editorial Committee (eds.). Flora of North America North of Mexico, Volume 28, New York and Oxford. Website: http://floranorthamerica.org/Main_Page [accessed Sept 2023].

Harpel, J.A. 1997. The phytogeography and ecology of mosses within the San Juan Islands, Washington State. Ph.D. dissertation, University of British Columbia, Vancouver, British Columbia. x + 275 pp.

Harpel, J.A., pers. comm. 2009. Communication with K. Sadler. 2009. Curator of Bryophytes, University of British Columbia Herbarium, Vancouver, British Columbia.

Hebda, R. 1997. Impact of climate change on biogeoclimatic zones of British Columbia and Yukon. Pp. 13-1 to 13-15, in E. Taylor and B. Taylor (eds.). Responding to global Climate Change in British Columbia and Yukon. Volume 1 of the Canada country study: Climate impacts and adaptation. Aquatic and Atmospheric Sciences Division, Environment Canada, Pacific and Yukon Region, and the Air Resources Branch, British Columbia Ministry of Environment, Lands and Parks. 363 pp.

Huang, H., R. Ye, M. Qi, X. Li, D.R. Miller, C.N. Stewart, D.W. DuBois, and J. Wang. 2015. Wind-mediated horseweed (Conyza canadensis) gene flow: pollen emission, dispersion, and deposition. Ecology and Evolution 5:2646-2658.

iNaturalist. 2023. Bartramia aprica. https://www.inaturalist.org/observations/108091978 [accessed Sept 2023].

Intergovernmental Panel on Climate Change (IPCC). 2013. Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK and New York, NY. Available: http://ipcc.ch/report/ar5/wg1/ [accessed Sept 27, 2023].

IUCN Standards and Petitions Committee. 2022. Guidelines for Using the IUCN Red List Categories and Criteria. Version 15. Prepared by the Standards and Petitions Committee. https://www.iucnredlist.org/documents/RedListGuidelines.pdf.

Kirchmeier-Young, M.C., N.P. Gillett, F.W. Zwiers, A.J. Cannon, and F.S. Anslow. 2019. Attribution of the influence of human-induced climate change on an extreme fire season. Earth’s Future 7(1):2-10. https://doi.org/10.1029/2018EF001050.

Lea, T. 2006. Historical Garry Oak ecosystems of Vancouver Island, British Columbia, pre-European contact to the present. Davidsonia 17(2):34-50.

Lee, O., pers. comm. 2018. Email correspondence to C. Webb. November 8, 2018. Bryophyte, Fungi and Lichen Collections Manager, University of British Columbia Herbarium, Vancouver, British Columbia.

Long, G. 2007. Biodiversity safety net gap analysis. Biodiversity British Columbia Technical Sub-Committee Component Report. Victoria, British Columbia. 66 pp. Website: www.biodiversityBritish Columbia.org [accessed June 14, 2021].

Lönnell, N., K. Hylander, B.G. Jonsson, and S. Sundberg. 2012. The fate of the missing spores—patterns of realized dispersal beyond the closest vicinity of a sporulating moss. PloS One 7(7): e41987. https://doi.org/10.1371/journal.pone.0041987.

MacDougall, A.S., B.R. Beckwith, and C.Y. Maslovat. 2004. Defining conservation strategies with historical perspectives: a case study from a degraded oak grassland ecosystem. Conservation Biology 18(2):455-465. https://doi.org/10.1111/j.1523-1739.2004.00483.x.

MacDougall, A.S., and R. Turkington. 2006. Dispersal, competition, and shifting patterns of diversity in a degraded oak savanna. Ecology 87(7):1831-1843.

MacDougall, A.S., and R. Turkington. 2007. Does the type of disturbance matter when restoring disturbance-dependent grasslands? Restoration Ecology 15(2):263-272.

Martin, T.G., P. Arcese, and N. Scheerder. 2011. Browsing down our natural heritage: Deer impacts on vegetation structure and songbird populations across an island archipelago. Biological Conservation 144 (1):459-469.

Maslovat, C., and L. Matthias. 2016. Species at Risk surveys in Mt. Maxwell Nature Trust Lands May/July 2016 – final report. Salt Spring Island Conservancy, Saltspring Island.

Maslovat, C., and L. Matthias. 2017. Species at Risk Surveys, Cyril Cunningham Nature Reserve, Saltspring Island. Salt Spring Island Conservancy, Saltspring Island, British Columbia. 5 pp.

Master, L.L., D. Faber-Langendoen, R. Bittman, G.A. Hammerson, B. Heidel, L. Ramsay, K. Snow, A. Teucher, and A. Tomaino. 2012. NatureServe Conservation Status Assessments: Factors for Evaluating Species and Ecosystem Risk. NatureServe, Arlington, VA. .

McIntosh, T.T. 2007. Report on a search for the Rigid Apple Moss on DND Property, Rocky Point, Vancouver Island, March 28 to 29, 2007. Natural Resources Canada and Canadian Forest Service, Victoria, British Columbia. 20 pp.

McIntosh, T.T. 2008. Report on a 2008 Survey for Rigid Apple Moss (Bartramia stricta) on the Lasqueti Island Ecological Reserve, Lasqueti Island, British Columbia Parks Canada Agency, Victoria, British Columbia. iii + 28 pp.

McIntosh, T.T., pers. comm. 2008. Correspondence to K. Sadler. 2008. Research and Faculty Associate, University of British Columbia (bryophytes and arid land vascular plants), Vancouver, British Columbia. Cited in COSEWIC 2009.

McIntosh, T.T. 2009a. Report on an inventory and a critical habitat assessment for Rigid Apple Moss (Bartramia stricta) at Mary Hill (DND), Vancouver Island. Department of National Defense, Victoria, British Columbia. iv + 34 pp.

McIntosh, T.T. 2009b. Report on an inventory and a critical habitat assessment for Rigid Apple Moss (Bartramia stricta) at Notch Hill (CFMETR – DND), Vancouver Island. Public Works and Government Services Canada, Victoria, British Columbia. iv + 30 pp.

McIntosh, T.T. 2012. Year 2 Report (2011-2012): A Long-term Bryophyte Monitoring Strategy for Rigid Apple Moss (Bartramia stricta) at Observatory Hill, Herzberg Institute of Astrophysics, Saanich, British Columbia. National Research Council Canada, Victoria, British Columbia. v + 41 pp.

McIntosh, T.T., and S. Joya. 2018a. Report on 2018 Surveys for Rigid Apple Moss and other At Risk Mosses at Mary Hill (DND), Vancouver Island. Natural Resources Canada, Victoria, British Columbia. iii + 42 pp.

McIntosh, T.T., and S. Joya. 2018b. Report on 2018 Surveys for Rigid Apple Moss and other At Risk Mosses at Notch Hill (CFMETR — DND), Vancouver Island. Natural Resources Canada, Victoria, British Columbia. iii + 31 pp.

McIntosh, T.T., and W. Miles. 2013. Year 3 Report, A Long-term Bryophyte Monitoring Strategy for Rigid Apple Moss (Bartramia stricta) at Observatory Hill, Herzberg Institute of Astrophysics, Saanich, British Columbia. National Research Council Canada, Victoria, British Columbia. iii + 28 pp.

McIntosh, T.T., and K.D. Sadler. 2011a. Results from a 2010 Rare Plant Survey at the Canadian Forces Maritime Experimental Test Ranges (CFMETR), Vancouver Island. Natural Resources Canada, Victoria, British Columbia. vi + 58 pp.

McIntosh, T.T., and K.D. Sadler. 2011b. Spring, 2011, Addendum to Results from a 2010 Rare Plant Survey at the Canadian Forces Maritime Experimental Test Ranges (CFMETR), Vancouver Island. Natural Resources Canada, Victoria, British Columbia. iv + 15 pp.

Metro Vancouver, Pacific Climate Impacts Consortium, and Pinna Sustainability. 2016. Climate projections for Metro Vancouver. 80 pp. Metro Vancouver, Burnaby, British Columbia.

Miles, W. 2015. Year 1 Report, Photo-Monitoring of Rigid Apple Moss (Bartramia stricta) at Observatory Hill, Dominion Astrophysical Observatory, Saanich, British Columbia. National Research Council Canada, Victoria, British Columbia. iii + 43 pp.

Miles, W. 2016. Year 2 Report, Photo-Monitoring of Rigid Apple Moss (Bartramia stricta) at Observatory Hill, Dominion Astrophysical Observatory, Saanich, British Columbia. National Research Council Canada, Victoria, British Columbia. iii + 76 pp.

Miles, W. 2017. Year 3 Report, Photo-Monitoring of Rigid Apple Moss (Bartramia stricta) at Observatory Hill, Dominion Astrophysical Observatory, Saanich, British Columbia. National Research Council Canada, Victoria, British Columbia. iii + 84 pp.

Miles, C.J., and R.E. Longton. 1992. Deposition of moss spores in relation to distance from parent gametophytes. Journal of Bryology 17(2):355-368.

Müller, F. 2014. Bartramia aprica — the correct name for the Mediterranean and western North American species historically recognized as “Bartramia stricta.” Herzogia 27(1):211-214.

NatureServe. 2020. Habitat-based Plant Element Occurrence Delimitation Guidance https://www.natureserve.org/sites/default/files/eo_specs-habitat-based_plant_delimitation_guidance_may2020.pdf [accessed June 29, 2022].

NatureServe. 2022. Climate Change Vulnerability Index — Canadian Version. https://www.natureserve.org/products/climate-change-vulnerability-index-canadian-version [accessed Oct. 2022].

NatureServe. 2023. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. http://explorer.natureserve.org [accessed Oct. 2018].

Neumann, K., J. Muñoz, and D. Quandt. 2019. Revisiting the Mediterranean Bartramia rosamrosiae with phylogenetic, morphological and ecological tools. [Abstracts from the 2019 joint conference between the International Association of Bryologists, the Spanish Bryological Society, and the International Molecular Moss Science Society, poster abstract PO-38]. The Bryological Times 149:66-67.

Noss, R.F., E.T. La Roe, and J.M. Scott. 1995. Endangered ecosystems of the United States: a preliminary assessment of loss and degradation. National Biological Service, U.S. Department of the Interior, Washington, D.C. 59 pp.

Nuszdorfer, F.C., K. Klinka, and D.A. Demarchi. 1991. Chapter 5: Coastal Douglas-fir Zone, Pp. 81-93 in Ecosystems of British Columbia, D. Meidinger and J. Pojar (eds.). British Columbia Ministry of Forests, Victoria, British Columbia. 330 pp.

Pacific Climate Impacts Consortium (PCIC). 2019. Plan2Adapt online tool. Summary of Climate Change for Georgia Depression.

Parks Canada Agency. 2011. Recovery strategy for the Rigid Apple Moss (Bartramia stricta Bridel) in Canada. Species at Risk Act Recovery Strategy Series. Parks Canada Agency. Ottawa. v + 44 pp.

PCIC (Pacific Climate Impacts Consortium). 2016. City of Vancouver climate impacts summary. Pacific Climate Impacts Consortium, University of Victoria, Victoria, British Columbia. 3 pp. Website: https://www.pacificclimate.org/resources/publications/city-vancouver-climate-impacts-summary [accessed June 14, 2021].

Pellatt, M.G., and Z. Gedalof. 2014. Environmental change in Garry Oak (Quercus garryana) ecosystems: the evolution of an eco-cultural landscape. Biodiversity and Conservation 23(8):2053-2067. https://doi.org/10.1007/s10531-014-0703-9.

Pellatt, M.G., Z. Gedalof, M.M. McCoy, K. Bodtker, A. Cannon, S. Smith, B. Beckwith, R.W. Mathewes, and D.J. Smith. 2007. Fire history and ecology of Garry Oak and associated ecosystems in British Columbia. Final report for IRFF Project 733. Parks Canada, Vancouver, British Columbia.

Pellatt, M.G., R.J. Hebda, and R.W. Mathewes. 2001. High-resolution Holocene vegetation history and climate from Hole 1034B, ODP leg 169S, Saanich Inlet, Canada. Marine Geology 174 (1 to 4):211-226. https://doi.org/10.1016/S0025-3227(00)00151-1

Roads, E., and R.E. Longton. 2002. Reproductive biology and population studies in two annual shuttle mosses. The Journal of the Hattori Botanical Laboratory 93:305-318.

Ryan, M.W. 1996. Bryophytes of British Columbia: rare species and priorities for inventory. Working Paper 12. Research Branch, British Columbia Ministry of Forests and Wildlife Branch, British Columbia Ministry of Environment, Lands and Parks, Victoria, British Columbia.

Sadler, K.D. 2007. Vegetation ecology of rock outcrop ecosystems of the Gulf Islands in the Coastal Douglas-fir Zone, British Columbia. Ph.D. dissertation, University of British Columbia, Vancouver, British Columbia. xvii + 143 pp.

Sadler, K.D. 2009. Report on a Survey for Bartramia stricta (Rigid Apple Moss) on Observatory Hill, Herzberg Institute of Astrophysics. National Research Council Canada, Victoria, British Columbia. iv + 14 pp.

Sadler, K.D. 2010. Survey for Bartramia stricta (Rigid Apple Moss) on Wymond Point and Windthrow Islands Trust Fund Covenant Lands at Sidney Island, British Columbia Islands Trust, Victoria, British Columbia. iii + 16 pp.

Sadler, K.D., M. Fairbarns, and W. Miles. 2009. Bartramia stricta (Rigid Apple Moss) on Observatory Hill, British Columbia. Field Survey Form (Plants), submitted to British Columbia Conservation Data Centre.

Sadler, K.D., and T.T. McIntosh. 2011. Report on a Long-term Bryophyte Monitoring Strategy for Rigid Apple Moss (Bartramia stricta) at Observatory Hill, Herzberg Institute of Astrophysics, 2010-2011 Surveys and Habitat Assessments, Year 1 Report. National Research Council Canada, Victoria, British Columbia. iv + 28 pp.

Salafsky, N., D. Salzer, A.J. Stattersfield, C. Hilton-Taylor, R. Neugarten, S.H.M. Butchart, B. Collen, N. Cox, L.L. Master, S. O’Connor, and D. Wilkie. 2008. A standard lexicon for biodiversity conservation: unified classifications of threats and actions. Conservation Biology 22:897-911.

Salt Spring Island Conservancy (SSIC). 2018. Excel spreadsheet of Rigid Apple Moss on Salt Spring Island to Aug. 2018.

Spittlehouse, D. 2008. Climate change, impacts and adaptation scenarios: climate change and forest and range management in British Columbia. Technical Report 45. British Columbia Ministry of Forests and Range, Forest Science Program, Victoria, British Columbia. viii + 38 pp.

Stewart, D. 2018a. Report on the 2018 Population Re-Assessment of Rigid Apple Moss (Bartramia stricta) on Lasqueti Island, British Columbia. Environment and Climate Change Canada, Vancouver, British Columbia. 21 pp.

Stewart, D. 2018b. Summary of Rigid Apple Moss (Bartramia stricta) Surveys in the Coastal Douglas-fir Ecosystems of the Powell River Regional District: 2017 to 2018. Environment and Climate Change Canada, Vancouver, British Columbia. 12 pp.

Thysell, D.R., and A.B. Carey. 2001. Quercus garryana communities in the Puget Trough, Washington. Northwest Science 75(3):219-235.

Tveten, R.K., and R.W. Fonda. 1999. Fire effects on prairies and oak woodlands on Fort Lewis, Washington. Northwest Science 73:145-158.

van Zanten, B.O. 1978. Experimental studies on transoceanic long-range dispersal of moss spores in the Southern Hemisphere. The Journal of the Hattori Botanical Laboratory 44:455-482.

van Zanten, B.O. 1984. Some considerations on the feasibility of long-distance transport in bryophytes. Acta Botanica Neerlandica 33:321-232.

Wang, T., A. Hamann, D. Spittlehouse, and C. Carroll. 2016. Locally downscaled and spatially customizable climate data for historical and future periods for North America. PloS ONE 11(6): e0156720. doi:10.1371/journal.pone.0156720.

Young, B.E. and G. Hammerson. 2016. Guidelines for using the NatureServe Climate Change Vulnerability Index. Version 3.0, Canada. NatureServe, Arlington. 61 pp.

Zanatta, F., J. Patiño, F. Lebeau, M. Massinon, K. Hylander, M. de Haan, P. Ballings, J. Degreef, and A. Vanderpoorten. 2016. Measuring spore settling velocity for an improved assessment of dispersal rates in mosses. Annals of Botany 118 (2):197‑206.

Biographical summary of report writer

Conan Webb has 17 years of experience as a field ecologist in species and ecosystems at risk stewardship and restoration projects in the Coastal Douglas-fir zone, focusing on Garry Oak ecosystems. In 2005, he graduated from the University of Victoria with a B.Sc. in Biology (focusing on botany and plant ecology). He worked with Parks Canada for 13 years on restoration projects for species and ecosystems at risk and on the production of two dozen recovery strategies for species at risk, including the Recovery Strategy for Rigid Apple Moss (Bartramia stricta Bridel) in Canada. As a consultant, he continues to work with species and ecosystems at risk, mapping rare element occurrences, providing assessments of and recommendations on development projects, and mentoring young people in nature connection activities.

Collections examined

The University of British Columbia Herbarium (University of British Columbia):

Location: Mt. Finlayson, Vancouver Island, British Columbia
Coll. Date: March 9, 2018
Accession No. B239400
Collector: Ryan Batten
Collector No: s.n.

Location: Mt. Tuam, Saltspring Island, British Columbia
Coll. Date: May 17, 2014
Accession No. B239402
Collector: Ryan Batten
Collector No: s.n.

Location: Reginald Hill, Saltspring Island, British Columbia
Coll. Date: May 29, 2014
Accession No. B239401
Collector: Ryan Batten
Collector No: s.n.

Appendix 1. IUCN threats assessment for the rigid apple moss. Only threat categories that were scored are shown.

Species Scientific name

Bartramia aprica

Elcode

NBMUS0R060

Assessor(s)

Assessment dated: 2019-08-14: Kristiina Ovaska (Moderator), René Belland (Co-chair), Conan Webb (SR writer); SSC members: Richard Caners, Jennifer Doubt, Nicole Fenton, Karen Golinski, Judith A. Harpel, Sean Haughian; jurisdictions and external experts: Greg Wilson (British Columbia), Jared Maida (CWS-Pac. Region), Brenda Costanzo (British Columbia), Kendra Bennett (British Columbia).

The calculator was modified and updated by K. Golinski and R. Belland on 28 June 2021 to reflect the revision of the threats section based on a more detailed understanding of threats.

References

COSEWIC status Report 2021; Bergamini et al. 2019

Assigned Overall threat impact:

A = Very high

Impact adjustment reasons:

No adjustment.

Overall threat comments

Generation time is 11 to 25 yrs.; three generations = 50 years based on long-lived species (perennial stayers, long-lived shuttles, dominants) (Bergamini et al. 2019). Threats calculator is based on 12 subpopulations.

Appendix 2. Results of the climate change vulnerability index for Rigid Apple Moss

The NatureServe climate change vulnerability index

* = Required field

Release: 3.01 - Canada

January 2016

Geographic area assessed:

SE Vancouver Island and Gulf Islands

Assessor:

René Belland, Karen Golinski

Species scientific name:

Bartramia aprica*

English name:

Rigid Apple Moss

Major taxonomic group:

Nonvascular Plant

Check if the species is an obligate of caves or groundwater systems:

S-Rank: S1
G-Rank: not applicable

Check if species is migratory and you wish to enter exposure data for the migratory range that lies outside of the assessment area:

Assessment notes (to document special methods and data sources):

Major sources of information for this assessment include: (1) COSEWIC. 2023. COSEWIC status Report on Rigid Apple Moss Bartramia aprica in Canada. 2-month Interim Status Report prepared for the Committee on the Status of Endangered Wildlife in Canada. (2) Nature Conservancy Climate Wizard. (3) Young, B. E. and G. Hammerson. 2016. Guidelines for using the NatureServe Climate Change Vulnerability Index. Version 3.0, Canada. NatureServe, Arlington.

Exposure: scope estimates (Section A) were based on % of all known sites in Canada exposed to each category of temperature and climate moisture deficit (CMD) severity, by consulting maps included in NatureServe 2016 and the Climate Wizard. BC 12/12 sites = 100% Change in Mean Annual Temperature (MAT) since 1950s and predicted to 2080s: BC >3.80 °C warmer. Change in climate moisture deficit (CMD) for the same period: BC >56.68 mm.

Sources for these trends: Young and Hammerson 2016, Figures 2, 3, 5, 6. Figure 6 also used for historical hydrological niche (C2bi).

Section A: Exposure to local climate change (calculate for species' range within assessment area)

Migratory exposure – climate change exposure index

Section B: Indirect exposure to climate change

Section C: Sensitivity and adaptive capacity

Section D: Documented or response to climate change

Climate Change Vulnerability Index for Bartramia aprica in SE Vancouver Island and Gulf Islands

Confidence in vulnerability sindex Score:

Extremely vulnerable

Very high

Climate exposure in migratory range:

(Scores are less reliable with more unscored factors):

not applicable

Definitions of Index Values:

Extremely Vulnerable (EV): Abundance and/or range extent within geographical area assessed extremely likely to substantially decrease or disappear by 2050.

Highly Vulnerable (HV): Abundance and/or range extent within geographical area assessed likely to decrease significantly by 2050.

Moderately Vulnerable (MV): Abundance and/or range extent within geographical area assessed likely to decrease by 2050.

Less Vulnerable (LV): Available evidence does not suggest that abundance and/or range extent within the geographical area assessed will change (increase/decrease) substantially by 2050. Actual range boundaries may change.

Insufficient Evidence (IE): Information entered about a species' vulnerability is inadequate to calculate an Index score.