Management plan for the Coastal Wood Fern in Canada [Proposed] 2011 : Species Information

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The coastal wood fern is an evergreen fern, 20–60 cm tall, which grows in vase-like clusters from a stout, short, creeping rhizome (Figure 1). The oblong lanceolate-shaped leaves are twice divided with deeply cut pinnae (primary division of a compound frond with leaflets on both sides of a central axis). The pinnules (secondary leaflet in a bipinnately compound frond) have small, spiny teeth along the margin. The rhizomes, stipes, and undersides of the pinnae have lance-shaped, chestnut-coloured scales (Douglaset al. 2000).

Figure 1. Illustration of the coastal wood fern. Used with permission from the University of Washington Press (Hitchcock et al. 1969. Illustrations by Jeanne R. Janish).

Botanical drawing of Coastal Wood Fern

The coastal wood fern is found along North America's west coast in British Columbia (B.C.), Washington, Oregon, and California; and inland in Montana and Arizona (NatureServe 2006). The Montana populations were not noted in the status report (COSEWIC 1998). The B.C. populations are approximately 250 km distance (disjunct) from the closest populations in Snohomish County, Washington State. Figure 2 outlines the North American distribution of this species.

Figure 2. North American distribution of coastal wood fern (from COSEWIC 1998)

Coastal Wood Fern distribution map in North America

In B.C. the distribution of the coastal wood fern is limited to eastern Vancouver Island and several adjacent northern Gulf Islands, including Denman and Hornby islands and several smaller islands in the Ballenas / Winchelsea Archipelago off the coast of Nanoose Bay (Figure 3) (COSEWIC 1998; B.C. CDC Element Occurrence Records 2006). The populations occur in a narrow rectangle measuring 6 km wide by 50 km long, totaling approximately 300 km2, with large expanses of water between populations. The area of occupancy for the coastal wood fern from Conservation Data Centre (CDC) records and recent surveys is approximately 1.9 ha.

B.C. supports less than 1% of the global abundance of this species. As of 2007, the total number of plants in B.C. is approximately 7500 (B.C. CDC Element Occurrence Data 2006; Maslovat, pers. obs. 2007).

Figure 3. Distribution of coastal wood fern in B.C. and Canada. Numbers for populations on Denman and Hornby Islands correspond to population names listed in Table 1.

Coastal Wood Fern British Columbian distribution map

There are 13 recorded populations in B.C. (Table 1) rather than 18 populations as listed in the status report (COSEWIC 1998). One location at Mount Finlayson, in Goldstream Provincial Park is unconfirmed and is not addressed in this management plan. Therefore, there are 12 extant populations in British Columbia.

Although two additional populations were found after the status report was written (B.C. CDC Element Occurrence Data 2006), some of the populations listed in the status report are now treated as subpopulations, since they are less than 1 km apart (a criteria used by the CDC for distinguishing populations). In this report, subpopulations less than 1 km apart are combined into one subpopulation, except for Amelia and Gerald islands, which are treated as separate populations because they are geographically isolated by the ocean.

(Note: With the exception of Henry (1915) the references in this table are denoting herbarium specimen collector and date, and not actual publications.)

Table 1. Status and description of coastal wood fern populations in B.C.
Population Status and description Land tenure
Mount Finlayson,
Vancouver Island
Henry (1915) referred to asAspidium rigidum. Not verified with herbarium specimen or later observations and is therefore considered to be a potentially historical location. Goldstream Provincial Park
Dorcas Point,
Vancouver Island
Herbarium specimen (Taylor 1963). Jamison (1996) observed 7 plants over 10 m2. Maslovat (2007) observed 2 subpopulations with 130 plants over 27 m2. Private
Amelia Island Douglaset al. (1998) observed 250 plants in 4 subpopulations over approximately 1500 m2. Provincial Crown
Gerald Island Jamison (1996) observed 300+ plants over 1.5 km2. Douglaset al. (1998) observed 475 plants in 8 subpopulations over 1540 m2. Private
Mistaken Island
Ballenas Islands
, south island
Douglaset al. (1998) observed 20 plants over 2m2.
First observed by A. Ceska in 1995 and 1996 (no number of plants or area of occurrence). Jamison (1996) observed 70+ plants over 50 m2. Douglaset al. (1998) observed 500 plants in 3 subpopulations (area of occurrence incomplete). Fairbarns and Miller (2005) observed several thousand reproductive fronds over 4,000–6,000 m2.
Private
Department of National Defence
Denman Island 1,
Boyle Point
Herbarium specimen (Roemer 1982). Jamison (1996) observed 120 plants in 25 clusters in 250 m2 split between two subpopulations. Williston (2006) observed 30 plants in southern subpopulations. Maslovat (2007) observed 220–270 plants over 260 m2 in 3 subpopulations. Boyle Point
Provincial Park
Denman Island 2
Repulse Point
Jamison (1996) observed 300+ plants over 800 m2. Maslovat (2007) observed 500 plants over 435 m2 in 2 subpopulations. Private
Denman Island 3
South/south east of Metcalf Bay
Herbarium specimen (Balke 1993). Jamison (1996) observed 40+ plants over 100 m2. Maslovat (2007) observed 175 plants over 250 m2. Private
Denman Island 4
South of Millard Rd
Jamison (1996) observed 150+ plants over 400 m2. Maslovat (2007) observed 75 plants over 270 m2. Private
Denman Island 5
Buckley Bay Ferry landing
First observed 1952. Herbarium specimen (Brayshaw 1968). Observed by Taylor (1968). Jamison (1996) observed 67 plants over 100 m2. Maslovat (2007) observed 73–93 plants over 100 m2 in two patches. Private
Hornby Island 1
Norman Pt. from south east of Ford's Cove to Downes Pt. in 7 subpopulations.
Herbarium specimen (Brayshaw 1968). Observed by Taylor (1968). Jamison (1996) observed 4000+ plants in 5 subpopulations over 2.4 km2. Douglaset al. (1998) observed 50–100 plants in 6 clumps at 2 subpopulations. Maslovat (2007) observed >3500 plants over 1.1 ha in 7 subpopulations. Private land + Camping Co-operative and Conservation organization
Hornby Island 2
East of Tribune Bay to north west of Helliwell Park
Herbarium specimen (Pojar 1976; Ceska and Ceska 1976). Jamison (1996) observed 160+ plants in 2 populations (42 clumps) over 920 m2. Douglaset al. (1998) observed 3000–6000 plants in 48 clumps at the southern subpopulation over 50–200 m2 Maslovat (2007) found over 1000 plants over 800 m2 (incomplete survey). Helliwell Provincial Park + private (portion protected in conservation covenant)
Hornby Island 3
Mount Geoffrey
Janszen observed in 1982. No numbers of plants or area of occurrence. Mount Geoffrey Escarpment Provincial Park

Summary of land tenure of known populations

In Canada, the coastal wood fern is limited to the Coastal Douglas-fir Biogeoclimatic Zone, moist maritime subzone (CDFmm) (B.C. CDC 2006). The coastal wood fern grows in coastal wooded slopes under open forest canopies of Douglas-fir (Pseudotsuga menziesii), Garry oak(Quercus garryana) or arbutus (Arbutus menziesii), and on rocky coastal bluffs and outcrops with stunted Garry oak (Quercus garryana) and oceanspray (Holodiscus discolor) (COSEWIC 1998; B.C. CDC Element Occurrence Records 2006). Plants growing on rocky outcrops and coastal cliffs show more signs of stress than plants found in coastal wooded habitats, such as smaller leaf blades and chlorosis (COSEWIC 1998). Plants growing in exposed habitats have also been observed to be less successful at overwintering (Martin, pers. comm. 2007).

Site aspect ranges generally from southwest to southeast, and one subpopulation occurs in a site with an east aspect. Elevation ranges from 0 to 120 m. Most populations occur on steep slopes, which range from 0 to 80%. Soils are mostly very dry to moderately dry, rapidly drained, and with moderate levels of nitrogen (COSEWIC 1998; B.C. CDC Element Occurrence Records 2006).

Information concerning the biology and ecology of the coastal wood fern is limited. Plants take 1–5 years to reach maturity and each fertile blade can produce as many as 13.5–15 million wind-dispersed spores. Some of the spores are retained on the blades over the winter and released the following spring. Spore viability averages three years or more for other Dryopteris species. In other fern species, spore germination, early gametophyte development, and gamete fusion occur when soils are moist in early spring (COSEWIC 1998). In California, coastal wood fern young sporophytes are found only in shaded areas with bare mineral soil (Veilleux, pers. comm. 2007). No prothalli (leaf-like structure bearing sexual organs) were noted during recent winter surveys in B.C., although survey time may not have been ideal (Maslovat, pers. obs. 2007).

The coastal wood fern can also reproduce vegetatively by rhizome elongation. Vegetative reproduction appears to be more common in dry, rapidly drained sites that are not ideal for spore germination and gamete fertilization (COSEWIC 1998).

The coastal wood fern is difficult to propagate ex situ from spores (Fraser, pers. comm. 2007; Furman, pers. comm. 2007; Wilson pers. comm. 2007). Horticultural propagation is via division of rhizome offshoots in the spring or autumn (Leigh 1999; Furman, pers. comm. 2007; Wilson, pers. comm. 2007).

Demographic collapse. The degree of sexual reproduction of the coastal wood fern in Canada is not known and may be a limiting factor. Although survey times were not ideal for finding prothalli, no evidence of sexual reproduction was found during winter surveys of Denman and Hornby Island populations (Maslovat, pers. obs. 2007). The ability of coastal wood fern populations to rebound from disturbances or extirpation may be hampered by a lack of sexual reproduction. There is a low probability this will influence recovery or management potential for the species.

Threats are defined as the proximate (human) activities or processes that have caused, are causing or may cause the destruction, degradation and/or impairment of biodiversity and natural processes. Threats can be past (historical), ongoing, and/or likely to occur in the future. Threats do not include intrinsic biological features of the species or population such as inbreeding depression, small population size and genetic isolation which are considered limiting factors.

The threat classification below is based on the IUCN-CMP (World Conservation Union- Conservation Measures Partnership) unified threats classification system and is consistent with methods used by the British Columbia Conservation Data Centre and the Conservation Framework. For a detailed description of the threat classification system see the IUCN-CMP website (IUCN and CMP 2006) and Master et al. (2009). Threats for the coastal wood fern were assessed for the entire province (Table 2).

Table 2. Threat classification table for coastal wood fern
Threat number Threat description Stress Scope1 Severity2 Timing3 Impact4 Sites
1 Residential & commercial development Small Serious High Low
1.1 Housing & urban areas Reduced population size
and viability, local
extirpation
Small Serious High Low Dorcas Point;
1 subpopulation at Hornby #1
6 Human intrusions & disturbance Small Moderate High Low
6.1 Recreational activities Reduced numbers of plants, direct mortality Small Moderate High Low 1 subpopulation at Denman #1;
2 subpopulations at Hornby #1;
potentially others
8 Invasive & other problematic species & genes Restricted Moderate-Slight High Medium-Low
8.1 Invasive non-native/alien species
  1. Resource competition leading to reduced growth and shading of seedlings;
  2. Reduced numbers of plants, direct mortality
Restricted Moderate-Slight High Medium-Low
  1. 1 subpopulation at Hornby #1; clumps at Hornby #2; potentially others
  2. Sudden Oak Death not yet observed at coastal wood fern locations in Canada
11 Climate change & severe weather unknown unknown Low N/A
11.4 Storms & Flooding Reduced viability, direct mortality of plants unknown unknown Low N/A Most threatened by erosion and storm damage: several subpopulations at Hornby #1;
1 subpopulation at Denman #1; Gerald Island and Ballenas Is.

1Scope – Proportion of the species that can reasonably be expected to be affected by the threat within ten 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%)

2Severity – 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 ten year or three-generation time frame. Usually measured as the degree of reduction of the species' population.
(Extreme = 71-100%; Serious = 31-70%; Moderate = 11-30%; Slight = 1-10%)

3Timing – High = continuing; Moderate = only in the future (could happen in the short term [less than 10 years or three 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.

4 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 stress 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%).

Land development activities such as housing development, threaten the coastal wood fern through habitat conversion and an increase in the potential for erosion in adjacent habitats. The population at Dorcas Point exists on land that has recently been subdivided into two lots. The environmental assessment on the Dorcas Point property recommends creating fenced covenant areas totaling 1090 m2 to protect the coastal wood fern population (Toth and Robert 2006). Construction of a residence may impact one subpopulation on Hornby Island ( Hornby Island #1). Although many of the populations on Denman and Hornby islands are on privately owned property, the coastal wood fern occurs on steep slopes that are generally not targeted for development.

Gerald and Mistaken islands are unlikely to be developed since they are remote and lack fresh water (Bartemucci, pers. comm. 2005). Threats associated with habitat conversion are minimal in Provincial Parks on Denman and Hornby islands, on provincially owned Amelia Island, and on the federally owned Ballenas Islands, which are not currently used for operational activities by the Department of National Defence (COSEWIC 1998; Cornforth, pers. comm. 2007).

Recreational activities currently threaten the coastal wood fern by trampling from pedestrian traffic and construction of hiking trails on or next to populations (COSEWIC 1998). Hiking trails on the steep slopes may also increase the potential for erosion.

One subpopulation in Boyle Point Provincial Park on Denman Island (Denman Island #1) is on a steep bluff approximately 10 m below a trail. Although the steep slope prevents access by most park visitors, in the past visitors have thrown beer cans and cigarette butts over the bluff, increasing the risk of accidental fire (Williston, pers. comm. 2006). However, it is not known if fire would be beneficial or not to the management of the species.

On Hornby Island, the subpopulations at Heron Rocks Camping Co-operative and Heron Rocks Friendship Centre (Hornby Island #1) are in areas that are used extensively by campers and their pets in the summer (Mogensen, pers. comm. 2007). Campers may harm plants by pitching their tents or constructing wooden shelters on or next to the coastal wood fern. The campgrounds are maintained by weed-whacking, which may damage plants.

Exotic alien plants, such as Himalayan blackberry (Rubus armeniacus), daphne (Daphne laureola), and periwinkle (Vinca major), and exotic grasses (e.g.,Dactylis glomerata) are present next to some populations of the coastal wood fern. Invasive plants may outcompete native species for moisture and light, and exotic grasses may form a thick thatch that prevents germination. Some of the plants in one subpopulation on Hornby Island (Hornby Island #1) have been smothered by invasive shrubs and other subpopulations on Hornby Island are threatened by invasive shrub encroachment.

IUCN #8. Invasive & other problematic species & genes (8.1 Invasive non-native species)

The coastal wood fern is a host for sudden oak death (Phytophthora ramorum) in the United States. The fungus has caused damage to the coastal wood fern plants, ranging from damage to the leaves to frond dieback to killing the plants (Garbelotto and Rizzo 2005; CDFA 2006). Although sudden oak death has been found in B.C., it has not been observed in the locations where the coastal wood fern is found (CFIA 2005).

IUCN #11. Climate change & severe weather (11.4 Storms & Flooding)

Storms threaten the coastal wood fern by eroding soil and dislodging or burying the plants. Extensive windstorms during the winter of 2006/2007 blew over many trees on Denman and Hornby islands increasing the potential for erosion and increased exposure to sun and wind. The populations on exposed rocky outcrops and very steep slopes, including several subpopulations on Hornby Island (Hornby #1), one subpopulation in Boyle Point Provincial Park (Denman Island #1), Gerald Island, and south Ballenas Island, are most threatened by erosion and storm damage (COSEWIC 1998; Maslovat, pers. obs. 2007). The effects of changes to the fire regime (i.e., fire suppression) in the species' habitat are also unknown.

The long-term management goal is to maintain all known populations at no less than their current size and to maintain the species' current distribution and area of occupancy in British Columbia.

There are currently 12 extant populations of the coastal wood fern in British Columbia. The distribution of the species is currently restricted, but there are no known extirpated populations that would indicate that the species was historically more abundant. The long-term goal to maintain all current populations is set to prevent further decline, range loss, or deterioration in status (National Recovery Working Group 2005).

The management objectives for the coastal wood fern are as follows:

  1. To establish habitat1 protection for all known populations.
  2. To assess the extent of and to mitigate the main threats (housing development/habitat conversion, recreational activities, and invasive alien plants) to the populations.
  3. To clarify the distribution of the coastal wood fern in British Columbia.
  4. To increase public awareness of the existence and conservation value of the coastal wood fern in areas with suitable habitat.
  5. To address knowledge gaps that prevent effective management of coastal wood fern (e.g., determine population trends, extent of occurrence, habitat attributes, type of reproduction, dispersal capabilities, genetic composition, significance of threats and natural disturbance) to ensure that populations remain at self-sustaining levels.

1 Protection can be achieved through various mechanisms including: voluntary stewardship agreements, conservation covenants, sale by willing vendors on private lands, land use designations, and protected areas.

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