Oregon Forestsnail (Allogona townsendiana): amended recovery strategy proposed 2024

Official title: Amended Recovery Strategy for the Oregon Forestsnail (Allogona townsendiana) in Canada [Proposed]

Species at Risk Act
Recovery Strategy Series

Proposed

2024

Preamble

Amended recovery strategy for the Oregon Forestsnail (Allogona townsendiana) in Canada (proposed 2024)

The Recovery Strategy for the Oregon Forestsnail (Allogona townsendiana) in Canada (Environment and Climate Change Canada 2016) was posted as final on the Species at Risk Public Registry in February 2016. Under sections 45,52 and 70 of the Species at Risk Act, the competent minister may at any time amend the recovery a recovery strategy, action plan and management plan, respectively.

The proposed amended recovery strategy includes:

• Proposed revised population and distribution objectives (PDO) aligned with the 2021 Species at Risk Policy on Recovery and Survival and related guidance
• Proposed updates and completion of the critical habitat identification based on new information and the revised PDO; and
• Alignment with current guidelines and templates for recovery documents

This amended recovery strategy was co-developed by staff from Environment and Climate Change Canada (ECCC) and the Province of British Columbia (B.C.).

Once this amended document is posted on the Species at Risk Public Registry as final it will replace the Recovery Strategy for the Oregon Forestsnail (Allogona townsendiana) in Canada (2016).

Preface

The federal, provincial, and territorial government signatories under the Accord for the Protection of Species at Risk (1996)^{Footnote 2} agreed to establish complementary legislation and programs that provide for effective protection of species at risk throughout Canada. Under the Species at Risk Act (S.C. 2002, c.29) (SARA), the federal competent ministers are responsible for the preparation of recovery strategies for listed Extirpated, Endangered, and Threatened species and are required to report on progress within five years after the publication of the final document on the Species At Risk Public Registry.

The Minister of Environment and Climate Change is the competent minister under SARA for the Oregon Forestsnail and has prepared this recovery strategy, as per section 37 of SARA. To the extent possible, it has been prepared in cooperation with the Province of British Columbia, as per section 39(1) of SARA.

Success in the recovery of this species depends on the commitment and cooperation of many different constituencies that will be involved in implementing the directions set out in this strategy, and will not be achieved by Environment and Climate Change Canada or any other jurisdiction alone. All Canadians are invited to join in supporting and implementing this strategy for the benefit of the Oregon Forestsnail and Canadian society as a whole.

This recovery strategy will be followed by one or more action plans that will provide information on recovery measures to be taken by Environment and Climate Change Canada and other jurisdictions and/or organizations involved in the conservation of the species. Implementation of this strategy is subject to appropriations, priorities, and budgetary constraints of the participating jurisdictions and organizations.

The recovery strategy sets the strategic direction to arrest or reverse the decline of the species, including identification of critical habitat to the extent possible. It provides all Canadians with information to help take action on species conservation. When critical habitat is identified, in either a recovery strategy or an action plan, SARA requires that critical habitat then be protected.

In the case of critical habitat identified for terrestrial species, including migratory birds, SARA requires that critical habitat identified in a federally protected area^{Footnote 3} be described in the Canada Gazette within 90 days after the recovery strategy or action plan that identified the critical habitat is included in the public registry. A prohibition against destruction of critical habitat under ss. 58(1) will apply 90 days after the description of the critical habitat is published in the Canada Gazette.

For critical habitat located on other federal lands, the competent minister must either make a statement on existing legal protection or make an order so that the prohibition against destruction of critical habitat applies.

If the critical habitat for a migratory bird is not within a federal protected area and is not on federal land, within the exclusive economic zone, or on the continental shelf of Canada, the prohibition against destruction can only apply to those portions of the critical habitat that are habitat to which the Migratory Birds Convention Act, 1994 applies as per SARA ss. 58(5.1) and ss. 58(5.2).

For any part of critical habitat located on non-federal lands, if the competent minister forms the opinion that any portion of critical habitat is not protected by provisions in or measures under SARA or other Acts of Parliament, or the laws of the province or territory, SARA requires that the Minister recommend that the Governor in Council make an order to prohibit destruction of critical habitat. The discretion to protect critical habitat on non-federal lands that is not otherwise protected rests with the Governor in Council.

Acknowledgments

This document has been updated from the recovery strategy prepared in 2016. This amended recovery strategy was completed by Jennifer Heron and Dawn Marks British Columbia Ministry of Water, Land and Resource Stewardship [WLRS]), and Eric Gross, Greg Rickbeil, and Megan Harrison (Environment and Climate Change Canada – Canadian Wildlife Service – Pacific Region [ECCC-CWS-PAC]).

Lea Gelling (British Columbia Conservation Data Centre) assisted with updated occurrence information on Oregon Forestsnail. Danielle Yu and Leon McCartney (ECCC-CWS-PAC) provided invaluable assistance with mapping and figure preparation.

Additional information on threats assessments, sites, natural history, and/or recovery actions was provided by Kristiina Ovaska, Lennart Sopuck, Ryan Durand, Joseph Carney, Tanya Bettles, Bill Harrower, Pamela Zevit, Patrick Lilley, Joanne Neilson, Ross Vennesland, Sofi Hindmarch, Markus Merkens, Lois Pittaway, Joshua Malt, Joanna Hirner, Angela Manweiler, and Beth Reimer.

Scientific and technical review was provided by Todd Kohler, Andrea Schiller, Cain van Cadsand, and Angela Manweiler (Department of National Defense); Lee Voisin, Noella Trimble, and Matt Huntley (ECCC-CWS-National Capital Region), Cassandra Harper (kʷikʷəƛ̓əm First Nation); Holly Bickerton (Parks Canada Agency); Kristiina Ovaska and Lennart Sopuck (Biolinx Environmental Research Ltd.); Michelle Franklin, Karen Clark, and Tamara Horechko (Agriculture and Agri-foods Canada); Andrea Shaw (B.C. Ministry of Agriculture and Fisheries), Alanah Nasadyk and Alana Phillips (WLRS); Grant Bracher (B.C. Ministry of Forests); and Ann Garibaldi (B.C. Ministry of Energy, Mines, and Low Carbon Innovation).

Executive summary

Oregon Forestsnail (Allogona townsendiana) was designated as Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) because it is restricted to a very small area of the southwestern British Columbia (B.C.) mainland and southern Vancouver Island. Subpopulations are severely fragmented with continuing declines observed in extent of occurrence and quality of habitat due mainly to urban development. The species is listed as Endangered in Canada under Schedule 1 of the Species at Risk Act (SARA). In B.C., Oregon Forestsnail is ranked S2 (Endangered) by the Conservation Data Centre and is on the provincial Red list. Recovery is biologically and technically feasible.

Oregon Forestsnail is a large hermaphroditic land snail endemic to western North America. The shell of mature individuals is pale brown or straw yellow, round and flattened in form, and ranges from 23 to 35 mm in diameter. Oregon Forestsnail is at the northern limits of its range in the Lower Mainland and Lower Fraser Valley of B.C., and, consequently, may possess unique adaptations.

Oregon Forestsnail occupies mixed-wood and deciduous forest habitat, typically dominated by Bigleaf Maple (Acer macrophyllum), Black Cottonwood (Populus trichocarpa), and scattered Western Redcedar (Thuja plicata). Many records are from riparian habitats and forest edges, where dense cover of low herbaceous native vegetation is typically present. The presence of Oregon Forestsnail is correlated with the presence of Stinging Nettle (Urtica dioica ssp.). All known Canadian Oregon Forestsnail subpopulations are from habitats lower than 500 m above sea level.

Major threats include residential and commercial development, recreational activities, and invasive non-native/alien species, some of which are known to directly consume snails while others are changing the species’ habitat.

The population and distribution objective is to recover the Oregon Forestsnail in Canada by improving redundancy and connectivity within the population, primarily through arresting the continuing decline in distribution and ensuring that habitat is maintained and/or restored between or within occupied patches.

Broad strategies in support of Oregon Forestsnail recovery are outlined in section 6.

Critical habitat for the Oregon Forestsnail has been identified to the extent possible. Sufficient critical habitat has been identified to support the population and distribution objective.

One or more action plans for the Oregon Forestsnail will be posted on the Species at Risk Public Registry within ten years of the publication of this document.

Recovery feasibility summary

Based on the following four criteria that Environment and Climate Change Canada uses to establish recovery feasibility, recovery of the Oregon Forestsnail has been deemed technically and biologically feasible. In keeping with the precautionary principle, this recovery strategy has been prepared as per section 41(1) of SARA, as would be done when recovery is determined to be technically and biologically feasible. This recovery strategy addresses the unknowns surrounding the feasibility of recovery.

1. Individuals of the wildlife species that are capable of reproduction are available now or in the foreseeable future to sustain the population or improve its abundance.

Yes. The persistence of Oregon Forestsnail subpopulations for at least 10 years at numerous sites (for example, Bridal Veil Falls and Cultus Lake Provincial Parks, Colony Farm Regional Park), combined with the known presence of juveniles/eggs at some sites, indicates that individuals capable of reproduction are available.

2. Sufficient suitable habitat is available to support the species or could be made available through habitat management or restoration.

Yes. Habitat modelling by ECCC-CWS (Rickbeil 2021) suggests that over 40,000 ha of habitat with the appropriate attributes to support Oregon Forestsnail still occur within the species’ Canadian range. Much of the remaining habitat is in small, isolated, and/or disturbed patches, so its ability to support Oregon Forestsnail subpopulations likely is limited (COSEWIC 2013). However, there are opportunities to restore habitat to improve patch size, condition, and connectivity.

3. The primary threats to the species or its habitat (including threats outside Canada) can be avoided or mitigated.

Yes. It is possible to avoid the threats of urban and agricultural development through habitat protection. Further, there are opportunities within some habitat patches to restore habitat to improve patch size, condition, and connectivity. Threats from the ecosystem modifications from introduced/non-native plant species or the spread of predatory non-native species may be more difficult to address although site-specific removal of introduced plant and snail species is possible. Threats such as fire and flooding also may be avoided or mitigated at some sites. Managing recreational activities to minimize soil compaction at some sites is also possible.

4. Recovery techniques exist to achieve the population and distribution objectives or can be expected to be developed within a reasonable timeframe.

Yes. Recovery planning techniques have been applied successfully to species with similar threats and requirements. Examples include habitat protection, removal of site‑specific threats (such as introduced predatory species and/or plants that cause ecosystem changes), revegetation of previously-cleared habitat, and working with land managers and landowners to develop site-specific best management practices guidelines. Captive rearing to supplement wild subpopulations is not considered an appropriate recovery technique or mitigation option.

1. COSEWIC* species assessment information

Date of assessment: May 2013

Common name (population): Oregon Forestsnail

Scientific name: Alllogona townsendiana

COSEWIC status: Endangered

Reason for designation: This large land snail is endemic to western North America. In Canada, it occurs mainly in the Lower Fraser Valley, the most densely populated and highly fragmented region of British Columbia. It also has been found at a single site on Vancouver Island. Habitat loss due to residential and commercial development continues to fragment and isolate remaining populations.

Canadian occurrence: British Columbia

COSEWIC status history: Designated Endangered in November 2002. Status re examined and confirmed in May 2013.

* COSEWIC (Committee on the Status of Endangered Wildlife in Canada)

2. Species status information

The legal designation for Oregon Forestsnail on SARA Schedule 1 is Endangered (2005). The species is not listed under the British Columbia (B.C.) Forest and Range Practices Act, Oil and Gas Activities Act, or Wildlife Act.

* Rank 1– critically imperiled; 2– imperiled; 3– vulnerable to extirpation or extinction; 4– apparently secure; 5– secure; H– possibly extirpated; NR – status not ranked.

3. Species information

3.1 Species description

Oregon Forestsnail (Allogona townsendiana W.G. Binney) (family Polygyridae) is a large hermaphroditic^{Footnote 4} land snail (adult shell diameter 23 to 35 mm) endemic to western North America (Figure 1). Snail shell colour varies, ranging from amber to light reddish brown to straw yellow, with white lines running across each segment of the spiral. The shell shape is round and slightly flattened. Adult shells typically have from 5.25 to 6 whorls with fine, wavy spiral striae^{Footnote 5} and irregular, light-coloured, wrinkle-like axial riblets^{Footnote 6}, and an overall irregular dimpled sculpture (Pilsbry 1940). As the snail ages, the outer periostracal^{Footnote 7} layer flakes and often becomes bleached, and the fine spiral striae are no longer evident. Fine hair-like structures, typical with other similar species, are not present on Oregon Forestsnail. The main distinguishing feature of Oregon Forestsnail adults is a distinct whitish apertural^{Footnote 8} “lip” or rim at the shell opening which is thickened and strongly flared outward. There is no denticle^{Footnote 9} within the shell aperture.

Figure 1. Oregon Forestsnail adults pictured topside (left), underside (centre), and underside of the shell showing the white apertural lip (right), June 11, 2010, Colony Farm Regional Park. Photographs by J. Heron.

Oregon Forestsnail eggs are round, globose, opaque, grayish-white, and slightly flattened, and have a grainy texture (Forsyth 2004; Steensma et al. 2009; COSEWIC 2002, 2013). Eggs are laid singly or in clusters with an average clutch size of 34 eggs in captivity (Steensma et al. 2009). Clutch size in situ has not been recorded. The average diameter of eggs laid in captivity is 3.1 mm (Steensma et al. 2009).

Adult and juvenile Oregon Forestsnails are similar in appearance although juvenile snails have thinner transparent shells, particularly towards the outermost whorl, and no bleaching of shell colour. Juveniles generally do not have a thickened apertural lip.

In general, the seasonal patterns of Oregon Forestsnail are as follows (summarized from COSEWIC 2013). This species is most active during the wet spring months when mating takes place. Mating begins in February and lasts through early June. Oviposition occurs after adult snails dig or burrow into new or existing nesting holes. Juvenile snails hatch approximately 8 to 9 weeks after oviposition (Steensma et al. 2009). As the warmer and drier summer months approach, snails seek shelter deep within litter, under logs or the bark of coarse woody debris, or in similar shelter places within the deciduous forests where they predominantly live (see 3.3 Needs of the Oregon Forestsnail). This aestivation period lasts a few months, and, in mid- to late September, snails become active again for the wet fall months. Oregon Forestsnails begin to enter hibernation around the first frosts. Winter hibernation begins sometime between late October and early November and can last until late February when temperatures are below 10.6°C (Steensma et al. 2009). During hibernation Oregon Forestsnails bury themselves 2 to 7 cm within leaf litter, moss, soil, or other forms of cover, form an epiphragm^{Footnote 10}, and orient themselves with the aperture of the shell upwards (Steensma et al. 2009).

Adults likely reach reproductive maturity by 2 years and have a life span of at least 5 (Steensma et al. 2009) to 8 years (COSEWIC 2002) although this is likely an underestimation. Based on the probable age at first reproduction and life span, generation time is approximately 4 to 6 years; the estimated average generation time is 5 years.

Oregon Forestsnail is unlikely to be confused with other landsnails within its B.C. range apart from Pacific Sideband (Monadenia fidelis). However, Pacific Sideband does not have a white, thickened apertural lip, and, when multiple specimens are compared, the overall size of mature Pacific Sideband is greater than Oregon Forestsnail. Morphological comparisons with other similar land snails found within the global geographic range of Oregon Forestsnail are detailed in the COSEWIC (2002; 2013) status reports.

3.2 Species population and distribution

The global range of Oregon Forestsnail is entirely within western North America (Figure 2). The northernmost extent of its range is in southwestern B.C. The range extends south through the Puget Trough in Washington State to the Willamette Valley in west-central Oregon. The easternmost records are from west of Hope, B.C., south-central Washington, and north-central Oregon in the Columbia River Valley (Forsyth 2004; Burke 2013). Based on recent records (within the past 10 years) and the historical records (combined), the global range extent is estimated at 135,000 km² (estimated from Burke 2013).

Figure 2. Global range of Oregon Forestsnail, based on Pilsbry (1940, Figure 508), Burke (2013), and B.C. records (B.C. Conservation Data Centre 2021). Published in COSEWIC 2002.

The Canadian range of Oregon Forestsnail is restricted to the coastal lowlands of the Lower Fraser Valley and one site on southeastern Vancouver Island in B.C. (Figure 3). Within the Lower Fraser Valley, the most northeastern record is near Hope, and the westernmost record is in Tsawwassen. On Vancouver Island, Oregon Forestsnail is known from the community of Westholme near Duncan (B.C. Conservation Data Centre 2020). All records are from elevations lower than 500 m above sea level.

Oregon Forestsnail records in B.C. date from 1901^{Footnote 11} to 2020 (COSEWIC 2002, 2013; B.C. Conservation Data Centre 2021). Based on verifiable records (for example, those from 1903 – 2020), the range extent for B.C. is estimated to be 4,425 km² (including the unsuitable salt-water Strait of Georgia, between Vancouver Island and the Lower Fraser Valley). The occurrence on Vancouver Island is <1.5 km². Both the historical and recent (within the past ten years) extents of occurrence are similar. The Canadian extent of occurrence is approximately 1% of the species global range (COSEWIC 2013).

Figure 3. Approximate Canadian range of Oregon Forestsnail (Allogona townsendiana) in southwestern British Columbia.

There are insufficient data to provide an accurate estimate of abundance of Oregon Forestsnail across the entire species’ range in B.C. However, Oregon Forestsnail sites mapped by the B.C. Conservation Data Centre (2021) and information gathered during the preparation of this document provide some information on Oregon Forestsnail abundance. At the site of the most studied subpopulation of Oregon Forestsnail in B.C. (Trinity Western University – Ecological Study Area [TWU-ESA]), density estimates within survey plots varied with an overall mean density of 1.0 snail/m² (Steensma et al. 2009). At another site of an Oregon Forestsnail subpopulation (Chilliwack), the estimated density ranged from 0.05 to 0.38 snails/m² (Hawkes and Gatten 2011; ISL 2015). Within dense Stinging Nettle-dominated patches in Colony Farm Regional Park, densities as high as 19 snails/m² have been recorded (Gross pers. comm. 2020). However, most studies to date have placed survey plots opportunistically within patches of high-quality habitat, rather than distributed randomly across broader sites, yielding density estimates that are not likely representative of all subpopulations, and so cannot be used to generate site-level subpopulation estimates.

There is minimal information on population fluctuation and trends for Oregon Forestsnail in Canada. Natural population fluctuations for snails are likely the result of numerous abiotic factors including moisture levels, weather patterns, and seasonal temperature fluctuations (such as early season frost) or erratic flooding. Biotic factors contributing to subpopulation fluctuations include parasites, predators, available minerals, nutrients for healthy shell growth (for example, through the consumption of plants such as Stinging Nettle), and availability of substrate within which to take refuge and/or lay eggs.

Although Canadian population trend data have not been collected for Oregon Forestsnail, associated Oregon Forestsnail habitat has shown a decline, particularly in the past 10 years. Urban and agricultural land development throughout the Lower Fraser Valley and southeastern Vancouver Island has removed its forested habitat, reduced wetland cover, and resulted in a loss of streams (see section 4 – Threats). As such, it is likely that historically Oregon Forestsnail exhibited a more extensive metapopulation structure within suitable habitats throughout its known range in southwestern B.C.

3.3 Needs of the Oregon Forestsnail

Oregon Forestsnail inhabits low elevation (<500 m above sea level) deciduous and mixed-wood forests with sustained high moisture and multi-structured microhabitat. Specific features and attributes must be present to support a number of critical life functions, including mating, egg-laying/incubation, aestivation/hibernation, foraging, and escape.

Topographic features and tree/shrub canopy to provide sustained moisture and leaf litter - all life functions

Moisture has a large influence on habitat suitability for Oregon Forestsnail. Snails are susceptible to dehydration and experience constant evaporative water loss through the lung surface and integument as well as through the constant deposition of a dilute mucous trail left during locomotion. Gastropods, such as Oregon Forestsnails, seek shelter and microhabitats that retain water and cool temperatures, and their activity patterns predominantly coincide with preventing dehydration (Prior 1985). Sites occupied by Oregon Forestsnail typically have topographic features that collect surface and/or sub-surface water and promote persistent high moisture (for example, ravines, gullies, or depressions).

Intact canopy (tree or tall shrub) is required to maintain/moderate site moisture and provide a source of leaf litter. Forest overstory is dominated (>40%) by deciduous tree species, and stand ages are >20 years (B.C. Conservation Data Centre 2021). Forest overstory composition includes large Bigleaf Maple (Acer macrophyllum), Black Cottonwood (Populus trichocarpa), and scattered Western Redcedar (Thuja plicata). Additional species present include Paper Birch (Betula papyrifera), Trembling Aspen (Populus tremuloides), Red Alder (Alnus rubra), and Grand-fir (Abies grandis) (B.C. Conservation Data Centre 2021). In some locations (for example, Colony Farm Regional Park), there is no tree canopy. Instead an extremely tall/dense shrub and herbaceous layer (including extensive Stinging Nettle, see below) serve the function of maintaining moisture and providing leaf litter. Oregon Forestsnail habitats have variable native shrub species composition (B.C. Conservation Data Centre 2021).

Dense understory vegetation – foraging and cover

Oregon Forestsnail inhabits areas with relatively dense herbaceous plant cover consisting of live and senescent^{Footnote 12} vegetation which provides food and cover during all life stages. Oregon Forestsnails also have been observed laying eggs at the base of vegetation, such as Creeping Buttercup (Ranunculus repens; Edworthy et al. 2012).

Most habitats of Oregon Forestsnail contain patches of Stinging Nettle (Edworthy et al. 2012; B.C. Conservation Data Centre 2021). The regular consumption of Stinging Nettle by snails likely is needed for healthy shell growth as the plant contains high levels of calcium and other essential minerals needed to maintain shell durability. Stinging Nettle is significant to other land snails (Iglesias and Castillejo 1998). Waldock (2002) examined the association of Oregon Forestsnail with the Stinging Nettle in detail at TWU-ESA in Langley and found a positive correlation between the abundance of the snails and Stinging Nettle. Most occurrences of Oregon Forestsnail in B.C. are from habitats that contain Stinging Nettle (B.C. Conservation Data Centre 2021). Stinging Nettle is associated with moist, rich soils with high amounts of nitrogen and phosphorus (Pojar and MacKinnon 1994). There are two subspecies of Stinging Nettle found in B.C. Urtica dioica ssp. dioica is native and Urtica dioicia ssp. gracilis is non-native (B.C. Conservation Data Centre 2021). It is unknown if Oregon Forestsnail exhibits a preference or obligate association with one or both Stinging Nettle species.

Cover and diggable substrate - egg-laying/incubation, aestivation/hibernation, shelter

Soils utilized by Oregon Forestsnail for egg-laying/incubation, aestivation/hibernation, and shelter are characterized by productive, moist, well-developed mull-type^{Footnote 13} litter layers, which provide sustained moisture and enable burrowing (Cameron 1986; COSEWIC 2002, 2013; Steensma et al. 2009; B.C. Conservation Data Centre 2021). Most snails dig new nests in the litter layer of soil although some nesting has been observed within pre-existing depressions in soil, in moss, and under coarse woody debris (CWD) (Steensma et al. 2009). During inactive periods, aestivation, and hibernation, Oregon Forestsnails seek shelter by burrowing into litter or moving under logs, the bark of CWD, the bases of Western Sword Fern (Polystichum munitum), or thick moss mats (Prior 1985; Steensma et al. 2009; Gross pers. comm. 2020). Hibernating individuals have been found buried up to 7 cm below the surface (Steensma et al. 2009).

Mating substrate - mating

Oregon Forestsnail mating has been observed directly on or within proximity (<3 m) of CWD (Steensma et al. 2009). Mating also can occur on other substrates described above.

3.4 Ecological roles

Oregon Forestsnail, as with other herbivorous land snails, performs important ecological functions in forest ecosystems as decomposers and consumers of live and decaying plant matter (see Mason 1970; Richter 1979, 1980ab; Gervais et al. 1998). Some species also function as dispersal agents for plant seeds and fungal spores, including fungi that form essential mycorrhizal associations with tree roots. The significance of the Oregon Forestsnail in such processes is unknown but may be considerable given the species’ relatively large size and local abundance in suitable moist habitats.

Oregon Forestsnail can be observed in high abundance at some sites (B.C. Conservation Data Centre 2021) and may provide a significant food source for other invertebrates, birds, and/or small mammals. In particular, the concentration of calcium within shells is likely a significant source for birds (for example, for eggshell growth; Graveland 1995; Mänd et al. 2000) or other invertebrates in the ecosystem. For example, the predatory snail, Robust Lancetooth (Haplotrema vancouverense), has been observed feeding on both eggs and juveniles of Oregon Forestsnail (Steensma et al. 2009; J. Heron pers. obs.). There are likely parasitic arthropods that rely on this species to complete their life history although any obligatory links between these species are not known.

3.5 Limiting factors

Limiting factors are generally not human-induced and include characteristics that make the species less likely to respond to recovery and conservation efforts. The main limiting factors for Oregon Forestsnail are speculative, but are likely a combination of the following:

• small subpopulation size and abundance
  • some Oregon Forestsnail subpopulations are within small, isolated and fragmented habitats and connectivity between these habitat patches has been lost. Small subpopulations in isolated and fragmented habitat have an increased risk of local extirpation
  • Oregon Forestsnail takes a minimum of two years to reach reproductive maturity (Steensma et al. 2009) and the average clutch size is 34 eggs. If egg and/or juvenile mortality is high, it may take considerable time for a subpopulation to recover
  • small and fragmented subpopulations could lead to genetic isolation and inbreeding depression
• limited dispersal ability. The dispersal ability of Oregon Forestsnail is likely poor, and it is unclear how much spatial area (habitat) is required to sustain a subpopulation within a site or habitat patch. Edworthy et al. (2012) observed a daily maximum dispersal distance of 4.5 m and a maximum displacement over three years of 32.2 m. Snails tend to be sedentary and cryptic animals, and their natural ability to colonize new areas is likely poor
• northernmost extent of global range. Oregon Forestsnail in Canada is at the northernmost extent of its global range which likely increases the species’ susceptibility to climatic and stochastic subpopulation fluctuations

4. Threats

Threats are defined as the proximate activities or processes that have caused, are causing, or may cause in the future the destruction, degradation, and/or impairment of Oregon Forestsnail in Canada. For purposes of threat assessment, only present and future threats are considered.^{Footnote 14} Threats presented here do not include biological features of the species or population (for example, inbreeding depression, small population size, and genetic isolation; or likelihood of regeneration or recolonization for ecosystems) which are considered limiting factors.^{Footnote 15} Historical threats, indirect or cumulative effects of the threats, or any other relevant information that would help understand the nature of the threats are presented in the Description of Threats section.

4.1 Threat assessment

The Oregon Forestsnail threat assessment is based on the IUCN-CMP (International Union for the Conservation of Nature–Conservation Measures Partnership) unified threats classification system (CMP 2010). For the most part, threats are related to human activities, but they can be natural. The impact of human activity may be direct (for example, destruction of habitat) or indirect (for example, invasive species introduction). Effects of natural phenomena (for example, fire, flooding) may be especially important when the species is concentrated in one location or has few occurrences, which may be a result of human activity (Master et al. 2009). As such, natural phenomena are included in the definition of a threat, but should be applied cautiously. These stochastic events should be considered a threat only if a species or habitat is damaged from other threats and has lost its resilience, and is, thus, vulnerable to the disturbance (Salafsky et al. 2008) so that this type of event would have a disproportionately large effect on the population compared to the effect it would have had historically.

^a Impact – The degree to which a species is observed, inferred, or suspected to be directly or indirectly threatened in the area of interest. The impact of each threat is based on Severity and Scope rating and considers only present and future threats. Threat impact reflects a reduction of a species population or decline/degradation of the area of an ecosystem. The median rate of population reduction or area decline for each combination of scope and severity corresponds to the following classes of threat impact: Very High (75% declines), High (40%), Medium (15%), and Low (3%). Unknown: used when impact cannot be determined (for example, if values for either scope or severity are unknown); Not Calculated: impact not calculated as threat is outside the assessment timeframe (for example, timing is insignificant/negligible or low as threat is only considered to be in the past); Negligible: when scope or severity is negligible; Not a Threat: when severity is scored as neutral or potential benefit.

^b Scope – Proportion of the species that can reasonably be expected to be affected by the threat within 10 years. Usually measured as a proportion of the species’ population in the area of interest. (Pervasive = 71–100%; Large = 31–70%; Restricted = 11–30%; Small = 1–10%; Negligible < 1%).

^c Severity – Within the scope, the level of damage to the species from the threat that can reasonably be expected to be affected by the threat within a 10-year or three-generation timeframe. Usually measured as the degree of reduction of the species’ population. (Extreme = 71–100%; Serious = 31–70%; Moderate = 11–30%; Slight = 1–10%; Negligible < 1%; Neutral or Potential Benefit ≥ 0%).

^d Timing – High = continuing; Moderate = only in the future (could happen in the short term [< 10 years or 3 generations]) or now suspended (could come back in the short term); Low = only in the future (could happen in the long term) or now suspended (could come back in the long term); Insignificant/Negligible = only in the past and unlikely to return, or no direct effect but limiting. For Oregon Forestsnail, the maximum generation time is 8 years = 24 year threat projection in the future.

4.2 Description of threats

This threats assessment has been updated from the COSEWIC (2013) status report and the 2012 Oregon Forestsnail Recovery Plan (Oregon Forestsnail Recovery Team 2012), and is updated with new information in part from a meeting held with biologists with regional expertise^{Footnote 16}. The updated threats assessment considers all potential habitat within the known range of the species around occurrences and additional local knowledge available on the habitat for each portion of the species’ range. Threats to Oregon Forestsnail are projected into the future for three generations (that is, 24 years).

The overall range-wide threat impact for Oregon Forestsnail in Canada is Very High‑High^{Footnote 17}. The overall threat impact considers the cumulative impact of multiple threats. The predominant threats are residential and commercial development, agricultural intensification, and ecosystem modifications that result from the cumulative effects of the spread of non-native species and recreational use.

Threat descriptions for low to very high impact threats are provided in sequential order as listed in Table 2 above.

IUCN-CMP threat 1 - Residential and commercial development (high – medium impact)

The majority of the Oregon Forestsnail’s range in Canada falls within or adjacent to lowland urban areas that are experiencing human population growth. Over 29,000 ha (66%) of modelled Oregon Forestsnail habitat (as per Rickbeil 2021) is located on lands where development for residential or commercial purposes is possible. Human activities associated with urban developments, specifically those that include clearing or removing Oregon Forestsnail habitat and/or altering natural hydrological patterns, can impact the microhabitat and overall forest stand structure necessary to sustain subpopulations of Oregon Forestsnail. Reducing habitat patch size through adjacent development also likely increases the remaining snails’ vulnerability to dehydration due to edge effects (for example, drying of the forest floor and harmful fluctuations in microclimate [Prior 1985; Burke et al. 1999]).

1.1 Housing and urban areas (high – medium impact)

The Lower Mainland and Lower Fraser Valley continue to experience rapid residential and urban development. Low elevation, flat areas are prime for development. Today, most of the remaining large natural habitats within the core range of Oregon Forestsnail are in private ownership. Each municipal government has an Official Community Plan with specific areas designated for future housing and commercial development to service the increase in human population. The B.C. Local Government Act requires a private landowner who is subdividing their property to dedicate 5% of the land subject to subdivision as a park or to pay cash in lieu of the land. This does not necessarily provide habitat for species at risk. However, local government may be more inclined to take monetary compensation that can then be allocated to community projects elsewhere in the municipality over park land if the Official Community Plan does not designate the type and location of future parkland. As well, if a property is developed but not subdivided (for example, building a home, barn), this designation is not required (Stewardship Centre for British Columbia 2016). Some municipalities have environmentally sensitive development permit areas and can direct development away from these sensitive areas with high ecological (for example, species at risk) values. However, if this is a gap in a municipality’s official community plan, then ecosystem values such as Oregon Forestsnail may not be protected. Looking forward three generations (that is, 24 years), it is likely a minimum of 11% of occupied natural Oregon Forestsnail habitat will be impacted by residential development. The severity is serious-moderate depending on the degree of habitat retention in different developments.

1.2 Commercial and industrial areas (low impact)

Industrial and business park expansion plans are published for some municipalities within the Lower Fraser Valley, and the scope, severity, and timing of potential commercial/industrial development impacts differ between each municipality. For example, the City in the Country Plan, specific to the City of Abbotsford, projects the need for “1,300 acres of employment-generating industrial and business park lands over the next 20 years” with “future residential development accommodated through hillside development…not accommodated by expansion into the Agricultural Land Reserve” (ALR) (City of Abbotsford 2004). As part of the development process, the City of Abbotsford ensures there are protection measures and wetland setbacks. These requirements concurrently protect Oregon Forestsnail habitats. However, they are only applicable where the two overlap. Large areas of South Surrey are designated for future office parks and light industrial buildings, and, at present, there is no requirement to survey for species at risk prior to development. Within Metro Vancouver, the areas zoned for industrial development are approximately 4% of the land base. The scope is considered small (likely a much smaller proportion of potential habitat at risk of commercial development versus residential). However, the severity is extreme due to the much lower levels of green space retention within commercial developments.

1.3 Tourism and recreational areas (low impact)

The demand for tourism and recreational areas within the Lower Fraser Valley and southeastern Vancouver Island has increased substantially within the past decade. Over 24% of modelled Oregon Forestsnail habitat (as per Rickbeil 2021) is located within parks (municipal, regional, or provincial) or on provincial Crown land. Within existing parks, as well as regional and municipal properties, habitat conservation and recreational development potentially conflict with Oregon Forestsnail conservation. Potential threats include construction of new trails and expansion of rights-of-way within highly used areas such as Colony Farm Regional Park, Brunette River Greenway, Brae Island, and Cheam Wetlands; creation of new camp sites (for example, Hope and Chilliwack areas); construction of dirt bike tracks (for example, areas adjacent to Bridal Veil Falls Provincial Park); and creation of golf courses in the Abbotsford, Chilliwack, and Hope areas. Undesignated provincial Crown land also experiences trail and off-road use by all-terrain vehicles (ATVs) (for example, dirt bikes). Expansion of recreational areas increases the frequency of road and trail building which may act as corridors (into natural habitats) that facilitate the rapid spread of invasive species (for example, plant seeds attach to tires and become dislodged at new sites) (Trombulak and Frissell 2000) (see IUCN-CMP Threat 7 and 8). All these expansion activities have potential to destroy Oregon Forestsnail habitat and/or cause mortality to snails.

IUCN-CMP threat 2 - Agriculture and aquaculture (medium impact)

2.1 Annual and perennial non-timber crops (medium impact)

Over 25% of Oregon Forestsnail modelled habitat (as per Rickbeil 2021) is located within the ALR. Forested habitat that is within the ALR is subject to clearing and conversion. Landowners/managers may clear land in anticipation of agricultural development, even where no actual crops or agricultural practices are planned for the immediate years (for example, recently cleared soil originally under forest canopy needs to be amended to support crops for human consumption). At present, there is no environmental assessment required for species at risk presence surveys before clearing of land for agricultural purposes. This is a potential threat at many agricultural sites within the Lower Fraser Valley where remnant verges of occupied natural habitat (for example, ditchside verges, crop verges, and the perimeter of agricultural fields) surround agricultural fields (Bettles pers. comm. 2020; Zevit pers. comm. 2020; Bianchini pers. comm. 2021). However, where the ALR overlaps within riparian areas that support fish and fish habitat, protective measures under the Fisheries Act apply, providing some indirect protection for Oregon Forestsnail habitat.

2.3 Livestock farming and ranching (low impact)

Detrimental impacts to Oregon Forestsnail habitat from livestock grazing (for example, horses, cattle, and sheep) have been recorded from at least three sites (B.C. Conservation Data Centre 2021). The impacts to gastropods from grazing are unknown, but trampling of sensitive riparian areas is often a result of livestock congregating adjacent to watercourses, and there would be direct mortality caused by trampling of individuals and habitat (for example, Stinging Nettle and other herbaceous plants). Within the municipalities from Langley to Hope, there are numerous dairy and chicken farms adjacent to natural forest and riparian areas. Large agricultural areas within the Lower Fraser Valley overlap with Oregon Forestsnail habitat, so the number of subpopulations impacted from livestock farming (for example, poultry, mink, pigs, elk, bison, goats, and others; BC Ministry of Agriculture 2017) is likely greater than from grazing. The scope of this threat is small; the severity is variable across different sites and grazing regimes, and the threat is ongoing.

IUCN-CMP threat 3 - Energy production and mining (low impact)

3.2 Mining and quarrying (low impact)

Gravel extraction and quarrying for road-building materials is a localized threat at sites in the Lower Fraser Valley, particularly on areas of Sumas Mountain. The overall footprint is small at this time but may expand in the future, and results in complete habitat loss where it occurs.

IUCN-CMP threat 4 - Transportation and service corridors (low impact)

4.2 Utility and service lines (low impact)

The Trans Mountain Expansion Project (TMEP) route from Hope to Burnaby, which involves twinning the existing Trans Mountain Pipeline, overlaps with Oregon Forestsnail habitat both within and adjacent to the existing right of way. The snail has been recorded from numerous sites throughout this corridor (B.C. Conservation Data Centre 2021). The construction of this pipeline is expected to impact snail subpopulations through direct mortality during construction and maintenance, direct habitat loss, and degradation of adjacent habitat through edge effects and introduction/spread of invasive non-native species. Though numerous sites have salvage and relocation components as mitigation measures.

Additional plans for expansion of hydro rights-of-way and infrastructure are ongoing throughout the Lower Fraser Valley, particularly in areas within large urban developments that require new/improved utility infrastructure. This habitat loss is not in the same areas as roads and the overall impacts are cumulative.

IUCN-CMP threat 5 - Biological resource use (low impact)

5.1 Hunting and collecting terrestrial animals (low impact)

There are a few observations of citizens collecting terrestrial snails for consumption (Durand pers. comm. 2020; Bianchini pers. comm. 2021). Snails also are collected for research purposes. The cumulative impacts of collecting snails is considered negligible to low. However, there is little information on this threat.

5.2 Gathering terrestrial plants (unknown impact)

With an increased awareness of local native plants and locally grown produce, the consumption of native species has grown in popularity. Stinging Nettle (ts’ex̱ts’ix̱: Sḵwx̱wú7mesh) is of cultural significance to Indigenous people in the region (Turner 2005). Indigenous peoples and other members of the public consume the plant. Some local farms provide Stinging Nettle to their subscribers. It is likely that these farms are just gathering the plant and not cultivating it (for example, crops), which could mean that the plant is being harvested from Oregon Forestsnail habitats. Some parks experience illegal Stinging Nettle picking by the public, such as Colony Farms Regional Park (Merkens pers. comm. 2020) and Bridal Veil Falls Provincial Park (Gross pers. comm. 2020).

Mushrooms (various species) also are illegally collected from parks and protected areas as well as harvested from provincial Crown lands. Searching for mushrooms occurs in the spring (March through June) and again in the fall (from September to November) and can involve clearing (either by hand or using a rake or other implement) the litter and duff^{Footnote 18} layers away to expose mushrooms growing under this cover. This practice also would expose resting, hiding, or hibernating snails and make them more vulnerable to dehydration, trampling, and predation. Mushrooms can also be hand-picked directly from the surface without clearing cover away, and it is a common practice for recreational harvesters to carry knives specifically to cut the fruiting bodies above ground and avoid disturbing the soil/mycelia. Hand-picking of other berry plants also occurs in the fall months, and people may inadvertently trample Oregon Forestsnails under these herbaceous plants.

The cumulative impacts of these practices at both at a local and range-wide scale is likely variable and site-specific. The threat impact to Oregon Forestsnail is unknown.

5.3 Logging and wood harvesting (low impact)

The B.C. range of Oregon Forestsnail has been impacted from extensive historical logging and forest resource extraction activities. The forest land base, particularly within the rural areas of Mission, Chilliwack, and Hope, continues to be intensively managed due to the high demand for forest products. Forest management practices, including pre-commercial thinning, pruning, removal of select tree species, fertilization practices, patch-size harvesting, and clearcut harvesting, likely have detrimental effects on subpopulations of Oregon Forestsnail. Oregon Forestsnail is not listed as Identified Wildlife under the B.C. Forest and Range Practices Act (FRPA), so is not afforded any protection from timber harvest

Pre-commercial thinning and pruning practices reduce the quantity and/or alter the timing of leaf and branch litter that would otherwise fall to the forest floor and provide shelter for Oregon Forestsnail. Pruning activities that remove lateral branches reduce the overall forest canopy, which results in lower relative humidity and subsequent desiccation^{Footnote 19} of the forest floor. The active removal of trees and use of heavy machinery may compact ground cover, crush individuals of Oregon Forestsnail, disturb CWD and shelter sites, and cause localized impacts within a harvested area. Present day intensive forest management practices target large dead CWD removal during the second rotation of forest harvesting. Thus, large CWD may be in short supply in intensively managed forests. These logs are likely important for maintaining stable microclimates for developing eggs, and thus are suitable microhabitat for Oregon Forestsnail.

Over 1,300 ha (approximately 3%) of modelled Oregon Forestsnail habitat (as per Rickbeil 2021) on provincial Crown land falls within active forestry licencee or permit areas and more occurs within the Timber Harvest Land Base where future logging is possible. Forest harvest is also possible on other land tenures (for example, private lands). There is also ongoing illegal harvest of old Western Redcedar for use in shake-block shingles, or other larger trees for arts and crafts-style products, throughout the range of Oregon Forestsnail (Yoder 2022). The scope is small (for example, <10 %), but the severity of logging differs depending on the site and activity, and it is scored with a broad range to reflect this uncertainty (for example, 11-70%).

IUCN-CMP threat 6 - Human intrusions and disturbance (low impact)

6.1 Recreational activities (low impact)

Recreational activities within Oregon Forestsnail habitat include camping, hiking (for example, Sumas Mountain Regional Park), foot and bicycle traffic (for example, Colony Farm Regional Park, Brunette River Greenway Regional Park), off-leash dog-walking (for example, most urban parks and undesignated provincial crown land), and the use of all-terrain vehicles and trail bikes (for example, private land), especially off-trail bikes (for example, Sumas Mountain). Such activities can result in degradation of habitat quality through soil compaction and also can cause accidental mortality especially along trail edges.

Effects from recreational activities can be pronounced in areas where the species is restricted to small habitat patches (for example, Brunette River Greenway Park [Metro Vancouver]; Neilson Park [Fraser Valley Regional District]; Colony Farm Regional Park [Metro Vancouver]). For example, inadvertent trampling of the site could result in significant mortality, especially during the spring breeding period when the snails are active on the forest floor.

Over 24% of modelled Oregon Forestsnail habitat (as per Rickbeil 2021) occurs either in parks (municipal, regional, or provincial) or on provincial Crown land where recreation pressure may exist. Areas with particularly high recreational use include habitats within Metro Vancouver and Fraser Valley Regional District parks; habitats on Sumas Mountain on B.C. Crown and private land (including local government land); portions of the TWU-ESA; and provincial parks such as Cultus Lake Provincial Park (Chilliwack) and Bridal Falls Provincial Park (west of Hope).

Hiking, ATV, and related activities also may increase the spread of introduced species (8.1). Recreational use of trails for horseback riding also likely impacts habitat (for example, trampling of trails/edges and defecation, which increases the spread of fungus, seeds).

The harvest of Stinging Nettle and mushrooms (5.2), Oregon Forestsnails (5.1) and other biological resources (5.2) within recreational areas is scored under other threat categories.

IUCN-CMP threat 7 - Natural system modifications (low impact)

7.3 Other ecosystem modifications (low impact)

Any activity that alters the habitat that sustains Oregon Forestsnail subpopulations is scored as an ecosystem modification. These habitat changes may occur as a result of fire suppression (which can limit the amount of early-seral deciduous forest represented on the landscape), road-building (which can alter watercourses and drainage patterns in adjacent Oregon Forestsnail habitat and thus impact site moisture), and introduction of invasive non-native plants (which can alter site moisture and change soil structure).

Deciduous-dominated forests develop naturally following localized disturbances, such as fire. Long-term fire suppression can result in landscapes dominated by coniferous forests which would reduce the amount of habitat available to support Oregon Forestsnail.

Oregon Forestsnail habitat includes ravines and gullies where both ephemeral and permanent natural watercourses flow. The construction of transportation routes through natural areas frequently results in changes to existing watercourses (for example, if a roadway bisects a creek; ongoing road and highway expansion projects include plans to divert, infill, and alter watercourses), which can alter moisture conditions within adjacent Oregon Forestsnail habitat. Within the geographic range of Oregon Forestsnail extensive roads and other similar transportation corridors already fragment much of the remaining natural habitat and contribute to other threats including increased frequency of use by humans (6.1). Roadsides act as corridors into natural habitats and are known to facilitate the rapid spread of introduced species (for example, plant seeds attach to car tires, and become dislodged at new sites) (Trombulak and Frissell 2000).

Some invasive plant species are known to change the forest floor vegetation and soil structure and facilitate an increase in light penetrating the understory vegetation to the forest floor. Increases in light levels lead to drier microclimate and understory conditions, and desiccation to the forest floor. They also increase dehydration stress to gastropods that depend upon high water and humidity levels. Invasive plants, such as Scotch broom (Cytisus scoparius), Gorse (Ulex europaeus), English Holly (Ilex aquifolium), Spurge-laurel (Daphne laureola), Yellow Archangel (Lamiastrum galeobdolon), and Cow Parsley (Anthriscus sylvestris) are likely to invade disturbed areas. English Ivy (Hedera helix) is known to spread and displace the native vegetation on forest floors. Native gastropods are not known to live within vegetation patches of English Ivy (Burke et al. 1999). Greater than 90% of known occupied sites have introduced species present, particularly Himalayan Blackberry (Rubus armeniacus) and other non-native plants. In one site on DND land, a previously-occupied monitoring plot was no longer occupied after becoming overgrown with Himalayan Blackberry (A. Manweiler pers, comm. 2022). English Holly and Himalayan Blackberry are also widely spread invasive plants within native ecosystems within southern Vancouver Island, and are known to displace native vegetation and may impact native Stinging Nettle. Oregon Forestsnail appears to be able to survive within habitat that has Himalayan Blackberry (for example, Colony Farm Regional Park). However, because the snail is long-lived (that is, up to 8 years), it is unknown whether there is successful mating, egg‑laying, and juvenile snail survival within areas of high invasive plant abundance. The threat of invasive species likely exists at all Oregon Forestsnail sites.

There are actions to remove or control the spread of invasive plants within many of the parks and protected areas where Oregon Forestsnail occurs. Invasive plants tend to be concentrated along trail and right-of-way edges, and control of the vegetation along these edges is part of maintaining trails for public use. Many park operators are aware of Oregon Forestsnail subpopulations and employ best management practices to sustain and enhance them, as well as minimize impacts of vegetation removal and public trampling (for example, Colony Farm Regional Park; Bridal Veil Falls Provincial Park; Cultus Lake Provincial Park).

IUCN-CMP threat 8 - Invasive and other problematic species and genes (unknown impact)

8.1 Invasive non-native/alien species/diseases (unknown impact)

This threat category refers to the invasive non-native/alien species that directly prey upon Oregon Forestsnail eggs, juveniles, or adults. Non-native plants alter the ecosystem processes and are considered an indirect threat to Oregon Forestsnail (for example, alter light levels, moisture regime, out-compete Stinging Nettle). They are considered under 7.3 Other ecosystem modifications.

Introduced gastropods and other invertebrate species have been recorded from most Oregon Forestsnail habitats although the scope of introduction and suite of species present is not fully known. Greater than 90% of sites have introduced species present, particularly gastropods, earthworms, and various Carabid beetles (B.C. Conservation Data Centre 2021).

Invasive terrestrial gastropods directly prey upon Oregon Forestsnail and may pose a threat to Oregon Forestsnail through competition for food and shelter or through predation (COSEWIC 2002). Rollo and Wellington (1979) demonstrated intra- and interspecific aggression among slugs and competition for refuges. Introduced gastropods of European origin are widespread in urban and agricultural areas within the Lower Fraser Valley and southern Vancouver Island, and several species have penetrated forested habitats (Forsyth 1999; 2001). These species continue to spread into new areas with inadvertent assistance from humans when nursery plants, garden ornamentals, or other materials with adhering soil are transported or when garden waste is discarded (Forsyth 1999).

Oregon Forestsnail subpopulations continue to persist despite widespread invasive non‑native invertebrates (high scope) throughout these same habitats but the severity and impacts are unknown.

8.4 Problematic species/diseases of unknown origin, and 8.6 Diseases of unknown cause (unknown impacts)

Within the past ten years, there has been extensive development within the geographic range of Oregon Forestsnail. During environmental assessment and development planning processes, various mitigation options have been proposed for Oregon Forestsnail. Among these mitigation proposals is the salvage and translocation of live Oregon Forestsnails to adjacent or nearby habitats. The potential for the spread of diseases due to the translocation of snails is unknown.

IUCN-CMP threat 9 - Pollution (medium – low impact)

9.3 Agricultural and forestry effluents (medium – low impact)

The use of pesticides, especially those aimed at gastropods, has potential to harm Oregon Forestsnail subpopulations by directly killing both individuals and eggs. The only application of pesticides that specifically target gastropods is likely to occur on privately owned properties close to houses, barns, or other human structures where Oregon Forestsnail is mistaken for a pest species. Overall, the general use of herbicides within parks and protected areas is diminishing due to municipal and regional bylaws that limit the use of these chemicals (for example, City of Richmond). Provincial initiatives that consider the ban on home use of pesticides for cosmetic purposes throughout B.C. are ongoing (B.C. Ministry of Environment 2009). However, pesticide bans are controversial in some municipalities (for example, Cassidy 2011).

Agricultural and forestry effluents are likely to harm Oregon Forestsnail habitat and individuals. For example, the use of herbicides to control regeneration of Bigleaf Maple on commercial forestry lands also may impact snail subpopulations in adjacent, mature stands through pesticide drift. Young Bigleaf Maple regeneration within conifer plantations competes with commercial tree species and herbicide treatments (either stump or foliage applications) are applied to control competing vegetation. This herbicide treatment can potentially harm or reduce habitat available to land snails.

Oregon Forestsnail is frequently recorded from forest and trail edge habitats, including those adjacent to well-used recreational trails within urban parks. Other land snails, such as Copse Snail (Arianta arbustorum), prefer moving along road verges (Baur and Baur 1990). Spraying herbicides to control road or trail-side vegetation likely harms gastropods within these verges, and the cumulative and persistent effects of herbicides within these environments may lead to long term declines in gastropod numbers (El‑Gendy et al. 2020). Herbicides are used less today since many municipalities have bans on certain herbicides, but it is unclear how extensive this practice was (or is currently) within the range of Oregon Forestsnail.

The close association of Oregon Forestsnail with Stinging Nettle may be indirectly detrimental to Oregon Forestsnail habitat. This is because Stinging Nettle may be targeted for removal in recreational areas with high human use due to the plant’s ability to cause skin irritation (for example, Glen Valley Regional Park and other parks with ball diamonds adjacent to natural areas).

Pesticide and fertilizer application in agricultural operations and in gardens could potentially threaten Oregon Forestsnail in habitats adjacent to the urban/agricultural interface through pesticide/fertilizer drift. The snail has been found adjacent to agricultural and urban areas although the overall impact to the species is unknown. Increasing blueberry acreage throughout the Fraser Valley includes many sites potentially adjacent to Oregon Forestsnail habitat. Concern for fruit pests such as Spotted Wing Drosophila (Drosophila suzukii) has resulted in the removal of hedgerow vegetation, a strategy used by some growers for controlling potential drosophila reservoirs. This in turn may be a problem for edge species such as Oregon Forestsnail.

This threat applies to numerous extant subpopulations, as well as potential habitats, although there are likely additional sites adjacent to agricultural areas where effluent run-off occurs.

IUCN-CMP threat 11 - Climate change and severe weather (low impact)

11.2 Droughts (unknown impact)

Increased summer droughts may affect occupied Oregon Forestsnail habitats by decreasing site moisture. Combined with other threats, such as water diversion and infilling (scored in 7.2), climate change-mediated drought could impact Oregon Forestsnail habitat within three generations. However, the magnitude and resulting impact of this threat to Oregon Forestsnail subpopulations is unknown.

11.4 Storms and flooding (low impact)

Much of the Oregon Forestsnail’s habitat is within the potential flood zone of the Fraser River or adjacent drainages (B.C. Ministry of Environment and Climate Change Strategy 2021). The greatest vulnerability to flood risk within the range of Oregon Forestsnail includes parts of Langley, Pitt Meadows, Chilliwack, Kent, Abbotsford, Tsawwassen, Mission, Hope, Port Coquitlam, and Surrey (Fraser Basin Council 2011). The Lower Fraser Valley has experienced major floods: the largest in 1894 and the second largest in 1948. Under climate change scenarios, there is predicted to be a 30% chance of a major flood occurring within the Lower Fraser Valley within the next 50 years (Fraser Basin Council 2011).

5. Population and distribution objective

The population and distribution objective is to recover the Oregon Forestsnail in Canada by improving redundancy and connectivity within the population, primarily through arresting the continuing decline in distribution and ensuring that habitat is maintained and/or restored between or within occupied patches.

Rationale

Oregon Forestsnail was assessed as Endangered^{Footnote 20} on the basis of a restricted extent of occurrence (EO) and index of area of occupancy (IAO)/distribution, combined with: (1) severe fragmentation; (2) observed continuing declines in EO and IAO, number of populations/locations, and area/extent/quality of habitat; and (3) a continuing decline in number of mature individuals inferred on the basis of observed habitat loss (COSEWIC 2013). The species’ EO prior to human impacts is unknown, but it is assumed that it was generally confined to the coastal lowlands of the Lower Fraser Valley (that is, restricted, even in its natural condition). However, the species’ habitat would not have been severely fragmented, and the occupied habitat/distribution (EO and IAO) would not have been declining. Addressing the continuing declines in distribution characteristics (that is, EO/IAO and fragmentation) is of primary importance in achieving a recovered condition for the species (that is, the survival characteristics that need to be improved to achieve recovery are redundancy^{Footnote 21} and connectivity^{Footnote 22} [ECCC 2020]). Recovery of the Oregon Forestsnail to a condition of Special Concern or Not at Risk is, therefore, focused on arresting further losses to the species’ EO/IAO, with particular focus on arresting further habitat fragmentation, and where possible, addressing existing fragmentation to improve habitat area and connectivity.

6. Broad strategies and general approaches to meet objectives

6.1 Actions already completed or currently underway

Habitat protection and restoration (in progress)

Oregon Forestsnail habitat adjacent to natural watercourses is protected indirectly through provisions of the B.C. Water Protection Act. It protects B.C.'s water by reconfirming the Province's ownership of surface and groundwater, and it defines limits for bulk water removal and prohibits the large-scale diversion of water between watersheds. The legislation does not address the protection of riparian habitat adjacent to watercourses.

Oregon Forestsnail habitat is protected indirectly through provisions in the Riparian Areas Protection Regulation (RAPR) under the B.C. Riparian Areas Protection Act which requires habitat buffers to remain around watercourses (depending on the size of the watercourse). Although the RAPR does not apply province-wide, it does apply to the Oregon Forestsnail's distribution in Canada except for federal lands, institutional developments, hydroelectric facilities, and farming, mining, and forestry activities. The RAPR mainly applies to housing and commercial developments. However, habitat buffer sizes are often not large enough to protect an entire subpopulation of the snail (that is, not all snail occurrences or habitats are within riparian areas). The B.C. Water Sustainability Act protects riparian vegetation below the high-water mark of a stream, lake, pond, wetland, and spring.

Oregon Forestsnail is recommended for listing as Identified Wildlife under the FRPA. At present, the species is not listed under this Act. If it is listed, it will be possible to protect some of the known habitat for this species within Wildlife Habitat Areas on provincial Crown land.

Oregon Forestsnail has been found in Bridal Veil Falls Provincial Park and Cultus Lake Provincial Park which are afforded protection through the legal provisions of the B.C. Park Act. Currently there are no specific management provisions within the respective park master plans for Oregon Forestsnail. However, park staff are aware of the Oregon Forestsnail occurrences in these popular recreational areas (Hirner pers. comm. 2020).

Metro Vancouver (regional district) land managers are aware of the Oregon Forestsnail and are working to incorporate best management practices into park maintenance planning within parks where the species has been recorded (Merkens pers. comm. 2020).

There are no local (municipal and regional) government bylaws that specifically protect Oregon Forestsnail. However, numerous development permit applications (depending on the jurisdiction) require environmental assessments that include wildlife values and consider impacts to natural habitats as part of the approval process. Some municipalities have an Official Community Plan that designates environmentally sensitive development permit areas and can direct development away from these sensitive areas with high ecological (species at risk) values.

Oregon Forestsnail subpopulations have been recorded from four private conservation areas in the Lower Fraser Valley. One is TWU-ESA, which is approximately 50 ha of habitat that is partially covenanted under the B.C. Ministry of Environment for the protection of fish habitat. The other three properties are owned and/or managed by the Fraser Valley Conservancy (Neilson pers. comm. 2020): South Fraser Way (1 ha); Auchenway (0.5 ha); and McKee Property (3.2 ha).

Oregon Forestsnails are included as a consideration in military Range Standing Orders and in site maintenance and development activity at the OPSEE Training Area (Department of National Defense; 3^rd Canadian Division Support Base Edmonton, Environment and Safety Services Detachment B.C. Mainland) in order to protect habitat and individuals (Manweiler pers. comm. 2020; Kohler pers. comm. 2021).

Best management practices guidelines for Oregon Forestsnail have been updated as of August 2018 (Heron pers. comm. 2020).

Habitat restoration projects have taken place in several sites in the Chilliwack area, including Cheam Wetlands Regional Park and Great Blue Heron Nature Reserve. Post‑restoration monitoring is ongoing.

Research and monitoring

From 2000 to 2011 there have been substantial search efforts and surveys for Oregon Forestsnail within the species’ range in B.C. (see Appendix A; COSEWIC 2013). Cumulative search effort has focused on southeastern Vancouver Island, many of the southern Gulf Islands, and areas throughout the Lower Fraser Valley and the Sunshine Coast. Survey effort also has focused on the edges of the species’ known range. Despite the intense search effort, there has been no substantial increase in the known range (COSEWIC 2002, 2013; B.C. Conservation Data Centre 2021).

Surveys by local conservancy groups for species at risk working on several of the Gulf Islands have not recorded Oregon Forestsnail (for example, Galiano, Mayne, Pender, Saltspring) and Vancouver Island (for example, Victoria Natural History Society). Surveys continued to 2020 although the species has not been recorded.

More recently (2013 to 2020) most Oregon Forestsnail occurrences have been recorded during environmental assessment processes and as part of proposed development projects (B.C. Conservation Data Centre 2020; Heron pers. comm. 2020). Many municipalities within the core range of Oregon Forestsnail require the reporting of species at risk during an assessment process (for example, Abbotsford, Surrey).

Oregon Forestsnail is easily identifiable and often recorded as an incidental observation submitted to the B.C. Conservation Data Centre (Gelling pers. comm. 2020). Ongoing stewardship and outreach work by local government biologists and conservancies continue to raise the profile of Oregon Forestsnail amongst professional biologists working within the species’ range. As a result, researchers, conservancies, biologists, naturalists, and members of the public voluntarily send records to the B.C. Conservation Data Centre (2021) and information on the species’ patchy distribution and habitat association has increased substantially. Many observations are now recorded on iNaturalist and other online forums.

A capture-mark-recapture study led by ECCC-CWS has been ongoing at Bridal Veil Falls Provincial Park since 2017 (Gross pers. comm. 2020).

Outreach

Oregon Forestsnail has been a focal outreach species for several conservation organizations operating in the Lower Fraser Valley (for example, South Coast Conservation Program, Fraser Valley Conservancy) (Neilson pers. comm. 2020; Zevit pers. comm. 2020).

6.2 Strategic direction for recovery

Table 3. Recovery planning table for Oregon Forestsnail

^a “Priority” reflects the degree to which the broad strategy contributes directly to the recovery of the species or is an essential precursor to an approach that contributes to the recovery of the species.

7. Critical habitat

Section 41(1)(c) of SARA requires that recovery strategies include an identification of the species’ critical habitat, to the extent possible, as well as examples of activities that are likely to result in its destruction. Critical habitat for Oregon Forestsnail is identified in this recovery strategy to the extent possible based on the best available information. The identified critical habitat is considered sufficient to meet the population and distribution objectives, therefore a schedule of studies is not required.

7.1 Identification of the species’ critical habitat

Critical habitat for Oregon Forestsnail is identified within southwestern British Columbia. The geospatial areas containing critical habitat for Oregon Forestsnail are presented in Figures 4-16. Within these geospatial areas, critical habitat is identified wherever any of the following biophysical attributes occur.

7.1.1 Biophysical attribute description

A description of the known biophysical features and attributes of the habitat that are required to support Oregon Forestsnail life-cycle processes (functions) in Canada are summarized in Section 3.3, Needs of the Oregon Forestsnail, and form the basis of the biophysical attribute description in Table 4 below.

7.1.2 Information and methods used to identify critical habitat

In order to arrest further losses to the species’ extent and distribution, and the availability/connectivity of suitable habitat therein, it was important to first spatially identify the species’ remaining habitat. A predicted habitat occupancy model^{Footnote 23} developed by ECCC-CWS (see Rickbeil 2021) served as the base layer from which geospatial areas containing critical habitat were selected. Input variables for the model included: over 1700 Oregon Forestsnail occurrence points from the B.C. Conservation Data Centre (2021) and an ECCC-CWS internal database; forest structure, composition, and disturbance variables extracted from Natural Resources Canada datasets (White et al. 2017); soils and watercourse data obtained from the B.C. Data Catalogue (catalogue.data.bc.gov); and topography variables extracted from Shuttle Radar Topography Mission (SRTM) data (Crippen et al. 2016). The Oregon Forestsnail range was broken up into approximately 0.28-ha modelling units, which corresponds with the approximate home range of an individual snail (Edworthy et al. 2012). Each unit was classified as predicted occupied, predicted not occupied, or no prediction (for example, where underlying input variables were missing and, thus, model predictions could not be generated). The full modelling procedures are outlined in more detail in a separate document (Rickbeil 2021), which is available upon request^{Footnote 24}.

Geospatial areas containing critical habitat for Oregon Forestsnail were derived through applying the following methods:

1. Fill model gaps to ensure that all occupied habitat is represented, reflecting the species’ current distribution.
   For occurrences located within modelling units where occupancy predictions could not be generated^{Footnote 25}, manually reclassify modelling units containing deciduous canopy^{Footnote 26} within 200 m^{Footnote 27} of the occurrence point(s) as occupied
2. Select all modelling units that were either model-predicted or manually-reclassified as ‘occupied’
3. Delineate discrete habitat patches:
   1. combine adjacent modelling units to delineate discrete habitat patches; and
   2. intersect the habitat patches with the Oregon Forestsnail occurrence database to classify patches as either:
      1. confirmed occupancy (intersect with a documented occurrence)
      2. unconfirmed occupancy (do not intersect with a documented occurrence)
4. Exclude isolated patches that were based on a single predicted-occupied modelling unit, to eliminate areas that are not actually part of the species’ current or potential distribution:
   Eliminate isolated (single) modelling units that were predicted by the model to be occupied based on localized variables but where the surrounding landscape context does not support Oregon Forestsnail presence (for example, small cluster of deciduous trees in a yard with no surrounding natural vegetation)
5. Select all habitat that is presumed occupied:
   1. select all patches with confirmed occupancy; and
   2. select patches with unconfirmed occupancy that are within 3 km^{Footnote 28} of a patch with confirmed occupancy
6. Apply a Critical Function Zone:
   Apply a 50-m^{Footnote 29} buffer to all presumed-occupied patches, to include surrounding forest and counter potential degradation of habitat as a consequence of edge effects

7.1.3 Geospatial location of areas containing critical habitat

The geospatial areas containing critical habitat for Oregon Forestsnail are presented in Figures 4-16. The 1 km x 1 km UTM grid overlay (red outline) shown on these figures is part of a standardized national grid system used to indicate the general geographic area within which critical habitat is found.

Within these polygons, only unsuitable areas that do not possess any of the features and attributes required by Oregon Forestsnail at any time are excluded from identification as critical habitat. Examples of these excluded areas include: cultivated and/or landscaped areas, buildings, roads, artificial surfaces, and waterbodies.

Figure 4. Overview of critical habitat for the Oregon Forestsnail in Canada. Critical Habitat is represented by the shaded yellow polygons where the criteria and methodology set out in Section 7.1.2 are met. Areas outside of the shaded polygons do not contain critical habitat. U.S.A. landbase (below dashed line) excluded.

Figure 5. Critical habitat for the Oregon Forestsnail on Southern Vancouver Island, B.C., is represented by the shaded yellow polygons where the criteria and methodology set out in Section 7.1.2 are met. The 1 km x 1 km UTM grid overlay (red outline) shown on this figure is part of a standardized national grid system used to indicate the general geographic area within which critical habitat is found. Areas outside of the shaded polygons do not contain critical habitat.

Figure 6. Critical habitat for the Oregon Forestsnail in Delta, B.C., is represented by the shaded yellow polygons where the criteria and methodology set out in Section 7.1.2 are met. The 1 km x 1 km UTM grid overlay (red outline) shown on this figure is part of a standardized national grid system used to indicate the general geographic area within which critical habitat is found. Areas outside of the shaded polygons do not contain critical habitat. U.S.A. landbase (below dashed line) excluded.

Figure 7. Critical habitat for the Oregon Forestsnail in Coquitlam, B.C., is represented by the shaded yellow polygons where the criteria and methodology set out in Section 7.1.2 are met. The 1 km x 1 km UTM grid overlay (red outline) shown on this figure is part of a standardized national grid system used to indicate the general geographic area within which critical habitat is found. Areas outside of the shaded polygons do not contain critical habitat.

Figure 8. Critical habitat for the Oregon Forestsnail at Stave Lake, B.C., is represented by the shaded yellow polygons where the criteria and methodology set out in Section 7.1.2 are met. The 1 km x 1 km UTM grid overlay (red outline) shown on this figure is part of a standardized national grid system used to indicate the general geographic area within which critical habitat is found. Areas outside of the shaded polygons do not contain critical habitat.

Figure 9. Critical habitat for the Oregon Forestsnail in Maple Ridge and Langley, B.C., is represented by the shaded yellow polygons where the criteria and methodology set out in Section 7.1.2 are met. The 1 km x 1 km UTM grid overlay (red outline) shown on this figure is part of a standardized national grid system used to indicate the general geographic area within which critical habitat is found. Areas outside of the shaded polygons do not contain critical habitat.

Figure 10. Critical habitat for the Oregon Forestsnail in Langley, B.C., is represented by the shaded yellow polygons where the criteria and methodology set out in Section 7.1.2 are met. The 1 km x 1 km UTM grid overlay (red outline) shown on this figure is part of a standardized national grid system used to indicate the general geographic area within which critical habitat is found. Areas outside of the shaded polygons do not contain critical habitat. U.S.A. landbase (below dashed line) excluded.

Figure 11. Critical habitat for the Oregon Forestsnail near Pitt Lake, B.C., is represented by the shaded yellow polygons where the criteria and methodology set out in Section 7.1.2 are met. The 1 km x 1 km UTM grid overlay (red outline) shown on this figure is part of a standardized national grid system used to indicate the general geographic area within which critical habitat is found. Areas outside of the shaded polygons do not contain critical habitat.

Figure 12. Critical habitat for the Oregon Forestsnail in Abbotsford, B.C., is represented by the shaded yellow polygons where the criteria and methodology set out in Section 7.1.2 are met. The 1 km x 1 km UTM grid overlay (red outline) shown on this figure is part of a standardized national grid system used to indicate the general geographic area within which critical habitat is found. Areas outside of the shaded polygons do not contain critical habitat.

Figure 13. Critical habitat for the Oregon Forestsnail at Nicomen to Harrison Mills, B.C., is represented by the shaded yellow polygons where the criteria and methodology set out in Section 7.1.2 are met. The 1 km x 1 km UTM grid overlay (red outline) shown on this figure is part of a standardized national grid system used to indicate the general geographic area within which critical habitat is found. Areas outside of the shaded polygons do not contain critical habitat.

Figure 14. Critical habitat for the Oregon Forestsnail in Chilliwack, B.C., is represented by the shaded yellow polygons where the criteria and methodology set out in Section 7.1.2 are met. The 1 km x 1 km UTM grid overlay (red outline) shown on this figure is part of a standardized national grid system used to indicate the general geographic area within which critical habitat is found. Areas outside of the shaded polygons do not contain critical habitat.

Figure 15. Critical habitat for the Oregon Forestsnail in Agassiz, B.C., is represented by the shaded yellow polygons where the criteria and methodology set out in Section 7.1.2 are met. The 1 km x 1 km UTM grid overlay (red outline) shown on this figure is part of a standardized national grid system used to indicate the general geographic area within which critical habitat is found. Areas outside of the shaded polygons do not contain critical habitat.

Figure 16. Critical habitat for the Oregon Forestsnail in Hope, B.C., is represented by the shaded yellow polygons where the criteria and methodology set out in Section 7.1.2 are met. The 1 km x 1 km UTM grid overlay (red outline) shown on this figure is part of a standardized national grid system used to indicate the general geographic area within which critical habitat is found. Areas outside of the shaded polygons do not contain critical habitat.

7.2 Activities likely to result in the destruction of critical habitat

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

Activities, described in Table 5, include those likely to cause destruction of critical habitat for the species. Destructive activities are not limited to those listed.

8. Measuring progress

The performance indicators presented below provide a way to define and measure progress toward achieving the population and distribution objective:

• human-caused destruction of Oregon Forestsnail critical habitat has ceased; and
• where fragmentation within critical habitat is evident, and habitat is restorable, restoration of degraded habitat has been initiated

9. Statement on action plans

One or more action plans for the Oregon Forestsnail will be posted on the Species at Risk Public Registry within ten years of the posting of the final recovery strategy.

10. References

Bains, B., A. Caldicott, and J. Heron. 2009. Surveys for gastropods, aquatic invertebrates and moths in the lower Fraser Valley, British Columbia, B.C. Min. Environ., Wildlife Science Section, Vancouver, B.C.

Baur, A., and B. Baur. 1990. Are roads barriers to dispersal in the land snail Arianta arbustorum? Can. J. Zool. 68:613–617.

B.C. Conservation Data Centre. 2021. B.C. Species and Ecosystems Explorer. B.C. Min. Environ., Victoria, B.C. <http://a100.gov.bc.ca/pub/eswp> [Accessed June 25, 2021].

B.C. Ministry of Agriculture. 2017. Census of Agriculture, Agriculture in Brief: Lower Mainland – Southwest. B.C. Ministry of Agriculture Corporate Statistics and Research Unit, adapted from Statistics Canada, Census of Agriculture 2016. 2 pp. <https://www2.gov.bc.ca/assets/gov/farming-natural-resources-and-industry/agriculture-and-seafood/statistics/census/census-2016/aginbrief_2016_lower_mainland-southwest_region.pdf?bcgovtm=buffer> [Accessed June 24, 2021].

B.C. Ministry of Environment. 2009. Cosmetic Use of Pesticides in British Columbia Public Consultation Paper. <https://www2.gov.bc.ca/assets/gov/environment/pesticides-and-pest-management/pesticide-use/consultations/consultationpaper.pdf> [Accessed June 23, 2021].

B.C. Ministry of Environment and Climate Change Strategy. 2021. Coastal Floodplain Maps. <https://www2.gov.bc.ca/gov/content/environment/air-land-water/water/drought-flooding-dikes-dams/integrated-flood-hazard-management/flood-hazard-land-use-management/floodplain-mapping/coastal> [Accessed June 24, 2021].

Burke, T. 2013. Land Snails and Slugs of the Pacific Northwest. Oregon State University Press, Corvallis, OR. 344 pp.

Burke, T., J.S. Applegarth, and T.R. Weasma. 1999. Management recommendations for survey and manage terrestrial mollusks 2.0. N. Duncan, ed. October 1999. <https://www.blm.gov/or/plans/surveyandmanage/files/mr-terrestrial-ig-1999-10-att1.pdf> [Accessed June 24, 2021].

Cameron, R. 1986. Environment and diversities of forest snail faunas from coastal British Columbia. Malacologia 27:341–355.

Cassidy, A. 2011. Pesticide ban too political (May 6, 2011). Coquitlam Now. <https://issuu.com/canwestcommunitypublishing/docs/coqfri20110506> [Accessed June 24, 2021].

City of Abbotsford. 2004. City in the country plan. Enhancing agriculture, preserving community sustainability final report. <https://abbotsford.civicweb.net/document/32039> [Accessed January 29, 2021]

COSEWIC (Committee on the Status of Endangered Wildlife in Canada). 2002. COSEWIC assessment and status report on the Oregon Forestsnail Allogona townsendiana in Canada. Ottawa, ON. vi + 20 pp.

COSEWIC (Committee on the Status of Endangered Wildlife in Canada). 2010. COSEWIC assessment and status report on the Threaded Vertigo Nearctula sp. in Canada., Ottawa, ON. x + 36 pp.

COSEWIC (Committee on the Status of Endangered Wildlife in Canada). 2013. COSEWIC assessment and status report on the Oregon Forestsnail Allogona townsendiana in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xii + 87 pp. <http://www.registrelep-sararegistry.gc.ca/default_e.cfm> [Accessed January 29, 2021].

CMP (Conservation Measures Partnership). 2010. Threats taxonomy. <http://www.conservationmeasures.org/initiatives/> [Accessed January 29, 2021].

Crippen, R., S. Buckley, E. Belz, E. Gurrola, S. Hensley, M. Kobrick, M. Lavalle, J. Martin, M. Neumann, Q. Nguyen, and P. Rosen. 2016. NASADEM global elevation model: methods and progress. International Society for Photogrammetry and Remote Sensing, Prague, Czechoslovakia July 12-19, 2016. <http://hdl.handle.net/2014/46123> [Accessed June 24, 2021].

Department of National Defence. 2009. Summary of Survey work for Blue-grey Taildropper slug (Prophysaon coeruleum) at CFB Esquimalt's Rocky Point and Colwood Properties in 2009. Formation Environment, Natural Resources Program, Victoria, B.C. Unpubl. Rep. 10 pp.

Edworthy, A., K. Steensma, H. Zandberg, and P. Lilley. 2012. Dispersal, home range size and habitat use of an endangered land snail, the Oregon Forestsnail (Allogonal townsendiana). Can. J. Zool. 90(7):875–884.

ECCC (Environment Climate Change Canada). 2020. Species at Risk Act Policies: Policy on Recovery and Survival. Species at Risk Act Policy and Guidelines Series. Ottawa, ON. 9 pp.

El-Gendy, K.S., A.F. Gad, and M.A. Radwan. 2020. Physiological and behavioural responses of land molluscs as biomarkers for pollution impact assessment; A review. Environmental Research 193:110558.

Forsyth, R.G. 1999. Distribution of nine new or little-known introduced land snails in British Columbia. Can. Field-Nat. 113:559–568.

Forsyth, R.G. 2001. First records of the European land slug Lehmannia valentiana in British Columbia, Canada. Festivus 33:75–78.

Forsyth, R.G. 2004. Land snails of British Columbia. Royal B.C. Museum, Victoria, B.C. 188 pp.

Fraser Basin Council. 2021. Lower Mainland Flood Management Strategy. <https://www.fraserbasin.bc.ca/water_flood.html> [Accessed June 24, 2021].

Gervais, J.A., A. Traveset, and M. Willson. 1998. The potential for seed dispersal by the Banana Slug (Ariolimax columbianus). Am. Midl. Nat. 140:103–110.

Graveland, J. 1995. Avian eggshell formation in calcium-rich and calcium-poor habitats: importance of snail shells and anthropogenic calcium sources. Canadian Journal of Zoology 74: 1035-1044.

Hawkes, V., and J. Gatten. 2011. Detailed survey and habitat assessment for Oregon Forestsnail (Allogona townsendiana) on military lands in Chilliwack, B.C. Final report project number CK 10949. Prepared for Angela Knopp, Department of National Defence Canada, ASU, Chilliwack, B.C, Natural Resources Program.

Iglesias, J., and J. Castillejo. 1998. Field observations on feeding of the land snail Helix aspersa Muller. J. Mollus. Stud. 65(4):411–423.

ISL Engineering and Land Services. 2015. Final Report – OPSEE Training Area Oregon Forestsnail 2013-2014 Oregon Forestsnail Monitoring Program.

Kremsater, L.L., and F.L. Bunnell. 1999. Edges: Theory, evidence, and implications to management of western forests. Pp. 117-153 in J.A. Rochelle, L.A. Lehmann, and J. Wisniewski (eds.) Forest Fragmentation: Wildlife and Management Implications. Brill, Leiden, Netherlands.

Liaw, A., and M. Wiener. 2002. Classification and regression by random forest. R news. 2(3):18-22.

Mason, C.F. 1970. Food, feeding rates and assimilation in woodland snails. Oecologia 4:358–373.

Mänd, R., V. Tiglar, and A. Leivits. 2000. Calcium, snails, and birds: A case study. Web Ecology 1:63–69.

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. <https://www.natureserve.org/sites/default/files/natureserveconservationstatusfactors_apr12.pdf> [Accessed April 2022].

NatureServe. 2022. NatureServe Explorer 2.0: An online encyclopedia of life [web application]. NatureServe, Arlington, Virginia. <http://explorer.natureserve.org> [Accessed July 7, 2022].

Oregon Forestsnail Recovery Team. 2012. Recovery plan for Oregon Forestsnail (Allogona townsendiana) in British Columbia. Prepared for the B.C. Ministry of Environment, Victoria, B.C. 50 pp.

Ovaska, K., R. Forsyth, and L.G. Sopuck. 2001. Surveys for potentially endangered terrestrial gastropods in southwestern British Columbia, April–October 2000–2001. Report prepared for Endangered Species Recovery Fund and Wildlife Habitat Canada by Biolinx Environmental Research Ltd., Sidney, B.C.

Ovaska, K., and L. Sopuck. 2000. Evaluation of the potential of terrestrial gastropods (slugs and snails) for monitoring ecological effects of logging practices on forest-floor conditions on Vancouver Island, British Columbia. A pilot study, October–November 1999. Report prepared by Biolinx Environmental Research Ltd. for Weyerhaeuser Company Ltd., Nanaimo, B.C. ;44 pp.

Ovaska, K., and L. Sopuck. 2001. Potential of terrestrial gastropods and salamanders as indicators for monitoring ecological effects of variable-retention logging practices. A pilot study, in the North Island Timberlands, May-November 2000. Report prepared by Biolinx Environmental Research Ltd. for Weyerhaeuser Company Ltd., Nanaimo, B.C. 105 pp.

Ovaska, K., and L. Sopuck. 2002a. Terrestrial gastropods and salamanders as indicators for monitoring ecological effects of variable-retention logging practices. A pilot study, May-October, 2001. Report prepared by Biolinx Environmental Research Ltd. for Weyerhaeuser Company Ltd., Nanaimo, B.C. 63 pp.

Ovaska, K., and L. Sopuck. 2002b. Surveys for terrestrial and freshwater molluscs on DND lands near Victoria, Vancouver Island, British Columbia. Report prepared by Biolinx Environmental Research Ltd. for DND/CFS Natural Resources Management Program, CFB Esquimalt, Victoria, B.C.

Ovaska, K., and L. Sopuck. 2003a. Terrestrial gastropods as indicators for monitoring ecological effects of variable-retention logging practices. Pre-disturbance surveys at experimental sites, May–October 2002. Unpublished report prepared by Biolinx Environmental Research Ltd. for Weyerhaeuser Company Ltd., Nanaimo, B.C. 55 pp.

Ovaska, K., and L. Sopuck. 2003b. Inventory of rare gastropods in southwestern British Columbia. Report prepared by Biolinx Environmental Research Ltd. for B.C. Ministry of Water, Land and Air Protection, Victoria, B.C.

Ovaska, K., and L. Sopuck. 2003c. Surveys for terrestrial gastropod species at risk in Pacific Rim National Park Reserve. Report prepared by Biolinx Environmental Research Ltd. for Parks Canada, Coastal British Columbia Field Unit, Victoria, B.C.

Ovaska, K., and L. Sopuck. 2004a. Surveys for terrestrial gastropods in the Pacific Rim, Gulf Islands, and Gwaii Haanas National Park Reserves Prepared for Parks Canada. Report prepared by Biolinx Environmental Research Ltd for Parks Canada, Coastal British Columbia Field Unit, Victoria, B.C.

Ovaska, K., and L. Sopuck. 2004b. Distribution and status of rare forest slugs in western Canada Results of 2003 and 2004 field seasons. Report prepared by Biolinx Environmental Research Ltd. for Endangered Species Recovery Fund (World Wildlife Fund and Environment Canada).

Ovaska, K., and L. Sopuck. 2005. Surveys for potential wildlife habitat areas for terrestrial gastropods at risk in southwest British Columbia: Autumn 2004 and Spring 2005. Prepared for B.C. Ministry of Water, Land and Air Protection, Victoria, B.C. 61 pp.

Ovaska, K., and L. Sopuck. 2006a. Surveys for terrestrial gastropods at risk in Pacific Rim National Park Reserve, 2006. Report prepared by Biolinx Environmental Research Ltd for Parks Canada, Western and Northern Service Centre, Victoria, B.C.

Ovaska, K., and L. Sopuck. 2006b. Surveys for the Blue-grey Taildropper and other gastropods at risk within CRD parks and trail systems in 2006. Report prepared by Biolinx Environmental Research Ltd. for Capital Regional District Parks, Victoria, B.C.

Ovaska, K., and L. Sopuck. 2007a. Surveys for the Blue-grey Taildropper slug (Prophysaon coeruleum) on federal lands on southern Vancouver Island, B.C, fall 2007. Report prepared by Biolinx Environmental Research Ltd. for CFS/CFB Esquimalt Natural Resources Program, Victoria, B.C.

Ovaska, K., and L. Sopuck. 2007b. Surveys for the Blue-grey Taildropper within CRD Parks and Trails System in 2007. Progress report prepared by Biolinx Environmental Research Ltd. for CRD Parks, Victoria, B.C.

Ovaska, K., and L. Sopuck. 2008. Surveys for the Blue-grey Taildropper and other gastropods at risk within the CRD Parks and Trails System in 2008. Report prepared by Biolinx Environmental Research Ltd. for CRD Parks, Victoria, B.C.

Ovaska, K., and L. Sopuck. 2009a. Surveys for the Blue-grey Taildropper slug (Prophysaon coeruleum) on federal lands on southern Vancouver Island in 2008. Report prepared by Biolinx Environmental Research Ltd. for CFS/CFB Esquimalt Natural Resources Program, Victoria, B.C.

Ovaska, K., and L. Sopuck. 2009b. Surveys for the Blue-grey Taildropper and other gastropods at risk at DND’s Royal Roads property, autumn 2009. Report prepared by Biolinx Environmental Research Ltd. for Department of National Defence, Formation Safety and Environment (CFB Esquimalt), Victoria, B.C.

Ovaska, K., and L. Sopuck. 2009c. Surveys for the Blue-grey Taildropper and other gastropods at risk within the CRD Regional Parks and Trails System in 2009. Report prepared by Biolinx Environmental Research Ltd. for CRD Parks, Victoria, B.C.

Ovaska, K., and L. Sopuck. 2010. Surveys for the Blue-grey Taildropper and other gastropods at risk with focus on Capital Regional District Parks, fall 2010. Report prepared by Biolinx Environmental Research Ltd. for Habitat Acquisition Trust, Victoria, B.C.

Ovaska, K., L. Sopuck, and J. Heron. 2011. Surveys for terrestrial gastropods at Burns Bog, October 2009 – March 2011. Report prepared by Biolinx Environmental Research Ltd. for B.C. Ministry of Environment, Victoria, B.C.

Parkinson, L., and J. Heron. 2010. Surveys for two invertebrate species at risk in southwestern British Columbia: Audouin’s Night-stalking Tiger Beetle (Omus audouini) and Oregon Forestsnail (Allogona townsendiana). B.C. Min. Environ., Terrestrial Conservation Science Section, Vancouver, B.C.

Peterson, E.B., N.M. Peterson, P.G. Comeau, and K.D. Thomas. 1999. Bigleaf maple managers’ handbook for British Columbia. B.C. Min. For., Research Program, Victoria, B.C. <www.for.gov.bc.ca/hfd/pubs/docs/mr/Mr090/Mr090.pdf> [Accessed June 24, 2021].

Pojar, J., and A. MacKinnon. 1994. Plants of coastal British Columbia. B.C. Min. For. and Lone Pine Publishing, Vancouver, B.C.

Prior, D.J. 1985. Water-regulatory behaviour in terrestrial gastropods. Biol. Rev. 60(3):403–424.

Richter, K.O. 1979. Aspects of nutrient cycling by Ariolimax columbianus (Mollusca: Arionidae) in Pacific Northwest coniferous forests. Pedobiologia 19:60–74.

Richter, K.O. 1980a. Evolutionary aspects of mycophagy in Ariolimax columbianus and other slugs. Pages 616–636 in D.L. Dindal, (ed.). Soil biology as related to land use practices. Proceedings of the VII International Colloquium of Soil Biology, USEPA Office of Pesticide and Toxic Substances, Washington, DC. EPA-560/13-80-038.

Richter, K.O. 1980b. Movement, reproduction, defense, and nutrition as functions of the caudal mucus in Ariolimax columbianus. Veliger 23:43–47.

Rickbeil, G. 2021. Oregon Forestsnail Critical Habitat Modeling Procedure and Results. Canadian Wildlife Service. 5 pp.

Rollo, C.D., and W.G. Wellington. 1979. Intra- and inter-specific agonistic behavior among terrestrial slugs (Pulmonata: Stylommatophora). Can. J. Zool. 57:846–855.

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. Conserv. Biol. 22:897–911.

Sopuck, L., and K. Ovaska. 2010a. Risk assessment for gastropods on the Winter Cove property of Gulf Islands National Park Reserve, March 2009. Report prepared by Biolinx Environmental Research Ltd. for Parks Canada, Sidney, B.C.

Sopuck, L., and K. Ovaska. 2010b. Survey for the Oregon Forestsnail at a proposed subdivision site on Matsqui Main IR #2, October 2010. Report prepared by Biolinx Environmental Research Ltd. for Matsqui First Nation.

Steensma, K.M.M., L.P. Lilley, and H.M. Zandberg. 2009. Life history and habitat requirements of the Oregon forestsnail, Allogona townsendiana (Mollusca, Gastropoda, Pulmonata, Polygyridae), in a British Columbia population. Invertebrate Biology 128:232 - 242.

Stewardship Centre for British Columbia. 2016. Green Bylaws Toolkit for Conserving Sensitive Ecosystems and Green Infrastructure. <http://www.greenbylaws.ca/> [Accessed June 24, 2021].

Trombulak, S., and C. Frissell. 2000. Review of ecological effects of roads on terrestrial and aquatic communities. Conservation Biology 14(1):18–30.

Turner, N. 2005. The Earth's Blanket. Douglas and McIntyre Ltd. 304 pp.

Waldock, S. 2002. A study of Allogona townsendiana and its correlation with Urtica dioica. Undergraduate thesis. Trinity Western University, Langley, B.C.

White, J.C., M.A. Wulder, T. Hermosilla, N.C. Coops, and G.W. Hobart. 2017. A nationwide annual characterization of 25 years of forest disturbance and recovery for Canada using Landsat time series. Remote Sensing of Environment 194:303-21.

Yoder, J.B. 2022. Dispatches from the redwood rebellion.Science376,1388-1388.

11. Personal communications

Bettles, Tanya. Environmental Coordinator, City of Abbotsford, Abbotsford, B.C.

Bianchini, Claudio. Bianchini Environmental Services, Delta, B.C.

Durand, Ryan. Durand Environmental Services, Nelson, B.C.

Gelling, Lea. Program Zoologist. British Columbia Conservation Data Centre, British Columbia Ministry of Environment and Climate Change Strategy, Victoria, B.C.

Gross, Eric. Environment and Climate Change Canada, Canadian Wildlife Service, Delta, B.C.

Heron, Jennifer. British Columbia Ministry of Environment and Climate Change Strategy, Conservation Science Section, Surrey, B.C.

Hirner, Joanna. Conservation Specialist, South Coast Region, B.C. Parks, North Vancouver, B.C.

Kohler, Todd. Department of National Defence, Biologist, Environment and Safety Services Detachment B.C. Mainland.

Manweiler, Angela. Department of National Defence, Environment Officer, Environment and Safety Services Detachment B.C. Mainland.

Merkens, Markus. Natural Resource Management Specialist, Regional Parks and Environment, Burnaby, B.C.

Neilson, Joanne. Executive Director, Fraser Valley Conservancy, Langley B.C.

Ovaska, Kristiina. Biolinx Environmental Research Ltd., North Saanich, B.C.

Sopuck, Lennart, Biolinx Environmental Research Ltd., North Saanich, B.C.

Zevit, Pamela. Biodiversity Conservation Planner, City of Surrey, Surrey, B.C.

Appendix A: Gastropod surveys

Appendix B: Effects on the environment and other species

A strategic environmental assessment (SEA) is conducted on all SARA recovery planning documents, in accordance with the Cabinet Directive on the Environmental Assessment of Policy, Plan and Program Proposals^{Footnote 30}. The purpose of a SEA is to incorporate environmental considerations into the development of public policies, plans, and program proposals to support environmentally sound decision-making and to evaluate whether the outcomes of a recovery planning document could affect any component of the environment or any of the Federal Sustainable Development Strategy’s^{Footnote 31} goals and targets.

Recovery planning is intended to benefit species at risk and biodiversity in general. However, it is recognized that strategies may also inadvertently lead to environmental effects beyond the intended benefits. The planning process based on national guidelines directly incorporates consideration of all environmental effects, with a particular focus on possible impacts upon non-target species or habitats. The results of the SEA are incorporated directly into the strategy itself, but also are summarized below in this statement.

This federal recovery strategy will benefit the environment by promoting the recovery of Oregon Forestsnail. The Oregon Forestsnail, as with other herbivorous land snails, performs important ecological functions in forest ecosystems as decomposers and consumers of live and decaying plant matter (see Mason 1970; Richter 1979, 1980ab; Gervais et al. 1998). Some species also function as dispersal agents for plant seeds and fungal spores, including fungi that form essential mycorrhizal associations with tree roots. The significance of the Oregon Forestsnail in such processes is unknown but may be considerable given the species’ relatively large size and local abundance in suitable moist habitats.

Oregon Forestsnail can be observed in high abundance at some sites (B.C. Conservation Data Centre 2020) and may provide a significant food source for other invertebrates, birds, and/or small mammals. In particular, the concentration of calcium within shells is likely a significant source for other invertebrates in the ecosystem. There are likely parasitic arthropods that rely on this species to complete their life history, although the obligatory links between these species are not fully known.

Habitat conservation for Oregon Forestsnail will indirectly benefit additional species at risk in the Lower Fraser Valley. The mixed deciduous lowland and riparian ecosystems of the Lower Mainland and southern Vancouver Island are overall at risk from urban and rural development, fragmentation, and ecological changes from introduced species. Ecosystems that are composed of older deciduous stands with a component of Bigleaf Maple and an extensive epiphyte component that includes club mosses (for example, Selaginella oregana) and abundant true mosses (Hylocomium splendens, Leucolepis menziesii, Isothecium stoloniferum, and Neckera menziesii), lichens (Cladonia, Nephroma, and Crocynia spp.), and Licorice Fern (Polypodium glycyrrhiza) are important for many species, including additional species at risk. These ecosystems would benefit from a detailed evaluation of habitat quality and threats facing them from human activities, and habitat work for Oregon Forestsnail will benefit this ecosystem. Older Bigleaf Maples support rich epiphyte (moss, lichen, liverwort, fern) communities and contribute significantly to nutrient cycling and calcium sequestration through the weight of their leaf fall, high nutrient content, and relatively rapid decay rates; and they provide abundant coarse woody debris and nurse logs when they fall (Peterson et al. 1999).

Coordinated, ecosystem-based approaches are needed to ensure Oregon Forestsnail recovery activities are compatible with recovery activities for other species and ecosystems within its range. Stewardship activities that result in protection or public awareness of the conservation values of Oregon Forestsnail habitat are expected to benefit all wild native species that use these ecosystems. The protection and/or suitable management of key areas will help to restore these ecosystems over the long term. There are no negative impacts anticipated as a result of recovery efforts for this species.