Management Plan for Coastal Wood Fern in Canada [Final] 2011: Threats

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).

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 habitat^[1] 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.

¹Protection 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.