Warning This Web page has been archived on the Web.

Archived Content

Information identified as archived on the Web is for reference, research or recordkeeping purposes. It has not been altered or updated after the date of archiving. Web pages that are archived on the Web are not subject to the Government of Canada Web Standards, as per the Policy on Communications and Federal Identity.

Skip booklet index and go to page content

Recovery Strategy for Multi-Species at Risk in Maritime Meadows associated with Garry Oak Ecosystems in Canada (Proposed)


Multi-Species Recovery

1.6 Common Limitations and Threats

There is a broad range of threats that directly affect maritime meadow species at risk and/or their habitats. The threats and the degree of threat affecting each species are listed in Table 4. The ranking of threats applies to confirmed populations although additional threats will likely also affect translocated populations. For both butterfly species, the importance of each threat relates to the potential effects of known extant, newly found, or reestablished populations (Miskelly and Heron, pers. comm.). In 2004 a population of Taylor's Checkerspot was confirmed on Denman Island. This population is on private lands and unknown before 2004 (Heron, pers. comm.). A matrix outlining the degree of each threat affecting each plant species at each confirmed location is included in a background document (Fairbarns and Maslovat 2005). The following threats are ranked roughly in descending order of importance for recovery although this may vary between species.

Table 4. Threats to habitat (H) and direct threats to the survival (D) of species at risk in maritime meadows
(For each species, threats are ranked as low, moderate, high or Unknown. Empty cells indicate the threat is not particularly relevant for that species.)
IM=island marble, TC=Taylor's checkerspot, BOC= bearded owl-clover, BFS=bear's-foot sanicle CSC=coastal Scouler's catchfly GP=golden paintbrush, PL=prairie lupine, PS=purple sanicle, SBL=seaside birds-foot lotus.
ThreatsEffectIMTCBOCBFSCSCGPPLPSSBL
1. Habitat destructionD, HHighHighHighHighHighHighHighHighHigh
2. Invasive plants
Invasive shrubsD, HHighHighHighLowHighHighHighMode-
rate
High
Invasive grasses and forbsD, HMode-
rate
Mode-
rate
HighMode-
rate
Mode-
rate
HighMode-
rate
HighHigh
3. Habitat fragmentationDHighHighMode-
rate
HighHighHighHighHighHigh
4. Changes in native vegetation composition from altered fire regimesD, HHighHighLowMode-
rate
Mode-
rate
Mode-
rate
HighMode-
rate
Mode-
rate
5. RecreationDMode-
rate
Mode-
rate
HighMode-
rate
LowMode-
rate
Un-
known
HighLow
6. Demographic collapseDMode-
rate
Mode-
rate
Mode-
rate
Mode-
rate
Mode-
rate
Mode-
rate
HighLowLow
7. MowingD, HMode-
rate
LowLowLow High   
8. Changes to hydrologyH  HighLowLowLow LowMode-
rate
9. Climate changeD, HUn-
known
Un-
known
Un-
known
Un-
known
Un-
known
Un-
known
Un-
known
Un-
known
Un-
known
10. Re-introduction of fireD, HHighMode-
rate
Un-
known
Un-
known
Un-
known
Un-
known
 Un-
known
Un-
known
11. Livestock grazingD, HHighLow       
12. Cutting or handpulling of invasive plantsD, HLowLowMode-
rate
LowMode-
rate
Mode-
rate
LowMode-
rate
Mode-
rate
13. Maintenance activitiesD  Mode-
rate
Mode-
rate
Mode-
rate
Mode-
rate
 Low 
14. HerbivoryD  LowLowLowLow Mode-
rate
Mode-
rate
15. PesticidesDMode-
rate
Mode-
rate
       
16. Landscaping with non-native plantsDLowLowMode-
rate
    Low 
17. Marine pollutionD ?
H?
  LowLowLowLow LowLow
18. Invasive invertebratesD      Un-
known
  
19. Invasive vertebratesD, H        Un-
known

1.6.1 Habitat destruction

Habitat destruction is listed as a primary threat for all of the plant species covered in this recovery strategy (Ryan and Douglas 1995; Ryan and Douglas 1996a, 1996b; Penny et al. 1998; Donovan and Douglas 2001; Penny and Douglas 2001; Fairbarns and Wilkinson 2003) and for Taylor's checkerspot (Shepard 2000c).

Although agricultural and urban development has likely eliminated both recorded and unrecorded populations of species addressed in this strategy in addition to maritime meadow habitat, most remaining patches of maritime meadows lie within protected areas or on federal lands (refer to Tables 11-17)

1.6.2 Invasive plants

Invasive species (exotic shrubs, grasses and forbs) are a prominent threat to Garry oak and associated ecosystems and to all of the species at risk in this recovery strategy (Fuchs 2001; GOERT 2002). Some invasive plants may increase nitrogen availability, thus changing ecosystem function (Maron and Connors 1996; Adair and Groves 1998; Levine et al.2003), pre-empt safe-sites for germinants (Brown and Rice 2000; Ryan and Douglas 1996a; Ryan and Douglas 1996b), alter litter layers (Facelli and Pickett 1991; Bergelson 1990), change the availability of soil moisture during different seasons and at different soil depths (Harris and Wilson 1970; Smith 1994), alter soil structure and composition (Levine et al. 2003), increase fire intensity by increased fuel loading (D'Antonio and Vitousek 1992) and compete with native plants for water, light and nutrients (Fuchs 2001; MacDougall, 2002).

Invasive plant species affect butterflies by competing with native larval and adult foodplants, preventing access to nectar plants and by changing the physical structure of the habitat (GOERT 2002; Vaughan and Black 2002a; 2002b).

For threats associated with different management activities, refer to Threats 7 (Mowing), 10 (Reintroduction of fire) and 12 (Cutting or hand-pulling of invasive plants).

1.6.3 Habitat fragmentation

Maritime meadow habitat is naturally fragmented, occurring on separate small islands and in pockets of Garry oak and associated ecosystems. However, recent habitat loss has accentuated the fragmentation by eliminating suitable habitat and the adjacent matrix. Habitat fragmentation may harm the long-term survival of a species by limiting restoration activities (e.g. preventing the reintroduction of fire in urban areas) and limiting dispersal of plants at risk and their pollinators (thereby potentially decreasing reproductive capability). Habitat fragmentation also creates dispersal barriers for seeds and butterflies, potentially limiting genetic diversity and decreasing the possibility of rescue effect (refer to Fuchs 2001 for a more comprehensive overview). Fragmented butterfly habitats may not support a wide enough range of habitat conditions to ensure that phenologically suitable foodplants are available to feed emerging larvae (refer to Fuchs 2001).

1.6.4 Changes in native vegetation composition from altered fire regimes

Although prior to European settlement many Garry oak and associated ecosystems had frequent, low-intensity burns initiated by First Nations (review in Fuchs 2001; Beckwith 2002), it is unclear how ubiquitous the use of fire was in maritime meadows. In areas with large First Nations populations (e.g. Vancouver Island), human-initiated burns probably played a significant role in maintaining meadows. Following European settlement, both cultural and natural fires were actively suppressed (Fuchs 2001; MacDougal et al.2004). Fire suppression allows the establishment and encroachment of native woody species in areas that were formerly open (Fuchs 2001), increases the buildup of aboveground biomass (grass and dead litter) and decreases the amount of exposed mineral soil providing safe sites for germination and establishment.

Plant communities that are dominated by herbaceous rather than woody species have more fine roots in the soil that produce organic matter as the roots decay root material. Low-intensity fires do not greatly reduce the organic component of the top layers of soil but do burn surface organic materials, releasing nutrients in forms available to plants. In ecosystems where the main inputs of organic matter come from herbaceous or deciduous woody plants rather than coniferous trees, the Ah horizon has a relatively neutral pH in sharp contrast to the acidic soils under Douglas-fir forests (Broersma 1973).

Woody plant encroachment may occur more rapidly on wetter portions of the landscape than in areas that experience deep, prolonged summer drought (GOERT 2002; Vaughan and Black 2002a; 2002b). Encroachment restricts native meadows to areas that are prone to drying out and plants experience premature senescence during times of drought. Premature senescence would reduce the number of larval and nectar plants available for butterfly species Hellmann (2002), Cappuccino and Kareiva (1985). As the phenology of remaining plants is temporally compressed, this can cause starvation of butterflies if foodplants dry out. The Helliwell Park population of Taylor's checkerspot may have been extirpated because the moister areas of the original grasslands, which previously contained late-season foodplants, have undergone encroachment by conifers.

The suppression of fires also influences the plant community in relation to exotic species invasion. Although some exotic species are favoured by fire (refer to Threat 2), regular fires can also reduce exotic herbaceous vegetation since many highly competitive exotic plants decrease under a regime of frequent burning (Tilman 1988 in MacDougall 2002; MacDougall pers. comm. 2004).

1.6.5 Recreational activities

Trampling from people and dogs can damage vegetation and all butterfly life stages. Bicycling, horseback riding and off-road vehicles can compact soil and damage both butterfly and plant species. Recreational use of horses may have been a factor in the recent extirpation of Taylor's checkerspot from at least two locations in Washington State (Vaughan and Black 2002b). Although light trampling may benefit some low-growing plant species (e.g. bearded owl-clover, bear's-foot sanicle) by reducing competition and suppressing tall exotic herbs (Penny et al. 1998), some species such as seaside birds-foot lotus are only found in locations with limited public access and are likely sensitive to trampling (Ryan and Douglas 1996a). The effect of dogs, especially in off-leash areas such as Macaulay Point, and the potential effects of escaped beach fires is not known.

Trial Island Ecological Reserve and Oak Bay Islands Ecological Reserve require permits to land marine craft, but there is no effective BC Parks management presence for enforcement. Municipal and Regional parks are both used extensively by the public and their pets, a trend that will continue to increase as Victoria's population increases. Some recent initiatives to control off-leash dogs in some jurisdictions have met with public opposition and have not been successful.

1.6.6 Demographic collapse

All of the species in this recovery strategy are limited to a small number of populations that have been genetically isolated from other populations. Genetic isolation can drive local adaptation, which is generally beneficial but can make a species less able to adapt to environmental changes. Genetic isolation can also lead to a limited gene pool, inbreeding depression and genetic drift (Primack 1993 in Donovan and Douglas 2000). Over time, these factors in combination with environmental limitations present at the periphery of a species range, can result in low seed set, low seedling vigour, low flowering rates, low resilience and low recruitment.

Habitat fragmentation and limited dispersal can also lead to demographic collapse and low seed set.

1.6.7 Mowing

Interactions between the autecology of the individual species and the timing of mowing will determine the effect of mowing on species at risk. For example, mowing may partically mimic some aspect of fire and may control shrub encroachment into meadows. Mowing may have a positive effect on low-growing species such as bear's-foot sanicle. However, mowing may have contributed to the extirpation of golden paintbrush from Beacon Hill Park (Hook pers. comm. 2004). Mowing at appropriate times should have minimal negative effects on reintroduced populations of Taylor's checkerspot larvae and pupae, which remain near the ground. However, mowing will likely negatively affect re-established island marble larvae, which are found 15-80 cm above the ground (Guppy pers. comm.2003; Miskelly pers. obs.2004).

In some parks including Glencoe Cove Municipal Park in Saanich and Beacon Hill Park in the municipality of Victoria, specific areas are either not mowed or are mowed late in the year (after mid-August) to minimize adverse effects to plants at risk (Daly pers. comm. 2004; Raeroer pers. comm.2004).

1.6.8 Changes to hydrology

Increased drainage, artificial ponding and elimination/diminution of water sources, notably vernal pools, can alter maritime meadows and degrade habitat. Irrigation common in urban areas and landscaped areas may encourage less stress-tolerant species, favouring exotic plant species. Landscaping adjacent to one bear's-foot saniclepopulation is heavily irrigated and may be affecting populations and limiting suitable habitat where the species may have once existed (Donovan and Douglas 2000).

1.6.9 Climate change

Climatic change may cause warmer summers and more compressed spring periods than existed formerly. These effects may combine with hydrological changes to cause the gradual disappearance of relict populations that no longer enjoy the climatic conditions that favoured their establishment.

1.6.10 Re-introduction of fire

Further research is needed to determine whether reintroducing fire is a viable restoration option. Increased fuel loading will cause fires to be hotter and more catastrophic than the more frequent, cooler fires that would have occurred prior to fire suppression.

The direct response of species at risk to controlled burns is not known but hot fires will likely kill invertebrates (Nicolai 1991, Swengel 1996 and Siemann et al. 1997 in Fuchs 2001). Individual species autecology and the timing of the burn will determine the degree of effect. Taylor's checkerspot pupae and larvae generally remain near the ground in cold or rainy weather and after they enter summer diapause (resting phase) (Guppy pers. obs. of Mill Bay population 2003; Hellman pers. comm. 2005; Ross pers. comm. 2004). The direct affect of a cool surface burn, completed at the appropriate time of the year, on the larvae or pupae of Taylor's checkerspot is not known. Guppy (pers. comm. 2004) suggests that burns may directly kill many eggs, larvae or pupae of the island marble; eggs and larvae are found on the foodplants (15-80cm above the ground) (Miskelly pers. obs. 2004), which are vulnerable to fire and pupae are above the soil surface but attached to objects near the ground. Fires, at least in the short-term, may also eliminate or limit larval foodplants of both butterfly species.

Although frequent burns appear to suppress adult exotic grasses such as Kentucky bluegrass (Poa pratensis) and orchardgrass (Dactylis glomerata) (MacDougall 2002), many exotic species, including Scotch broom and common velvet-grass (Holcus lanatus) are favoured by fire and readily colonize any post-burn mineral soil that is exposed. While Scotch broom can increase after a single fire, it is not favoured by repeated burns. The presence of these exotic species, can in turn increase the flammability of ecosystems (D'Antonio and Vitousek 1992).

1.6.11 Threats with livestock grazing

Livestock were formerly grazed on Discovery, Trial, Chatham, Strongtide, VanTreight, and Griffin Islands. Intensive grazing coupled with cultivation and the introduction of exotic species dramatically altered Garry oak ecosystems, including maritime meadows (MacDougall et al. 2004). Grazing likely shifted the species composition, vegetation structure and nutrient cycling of these ecosystems (Hatch et al. 1999; Bartolome et al. 2004). Feral goats continue to graze Brown Ridge on Saturna Island. Site-specific consideration of the impacts of livestock grazing on maritime meadows will be needed before altering particular management regimes, as grazing can suppress shrub invasion (hence reduce other threats to the species of concern).

Livestock grazing tips the competitive balance of communities in favor of unpalatable species and, if grazed at the wrong time of year (i.e. spring), may decimate palatable species such as seaside birds-foot lotus. Grazing favours sod-forming grasses and overgrazing can also play a major role in the establishment and eventual dominance of exotic forage species (Saenz and Sawyer 1986 in Fuchs 2001) (refer to Threat 2). Grazing tramples butterfly larvae and may eliminate larval foodplants. Depending on the timing of grazing, island marble eggs and larvae may be consumed. Therefore, if grazing is to be ongoing in these ecosystems, knowledge of the phenology of plants and invertebrates (in particular lepidopterans) will be required to minimize damage to important life cycle stages.

1.6.12 Cutting and hand pulling of invasive plants

Managing invasive species may also affect species at risk. Habitat restoration for both butterfly species, which feed on exotic host plants, should focus on reintroductions of native foodplants rather than retaining exotic host plants such as ribwort plantain (Plantago lanceolata) for Taylor's checkerspot and introduced weedy mustards for island marble.

The issue of providing suitable habitat for butterfly species through maintenance or encouragement of exotic host plants was considered. Such actions may be further considered in the development of a recovery action plan.

Hand pulling, or cutting invasive shrubs and piling and removal of slash material may trample plant species at risk. These activities may also damage all butterfly life stages and their foodplants. Many invasive plants are particularly adapted to colonize disturbed soils and the soil disturbance associated with invasive species removal may increase invasion by seedlings (Knops et al. 1995; Kotanen 2004). Ineffective control techniques (e.g. cutting young broom at stem level) may also threaten populations.

Other invasive species management tools include mowing (Threat 7) and prescribed burning (Threat 10).

1.6.13 Maintenance activities

Maintenance activities around radio towers (e.g. Seacoast Communications lease on Trial Island, on Department of National Defence lands and in parks) can damage species at risk. Potential threats include mowing (Threat 7), herbicide application, trampling, placement of heavy wires across the ground, stockpiling of materials and garbage, facility maintenance and transport of heavy materials and equipment from dock to facilities (Penny and Douglas 2001).

1.6.14 Herbivory

The concentration of native grazers and their herbivory patterns have changed with increased urbanization and habitat loss. Roosevelt elk (Cervus elaphus roosevelti), which were formerly more common in Garry oak and associated ecosystems, are now rarely encountered only in less populated areas of Vancouver Island. Columbian black-tailed deer (Odocoileus hemionus columbianus) are now more densely concentrated on a smaller landbase than formerly. Development, decreased hunting, and fewer carnivores than formerly in populated areas have increased the density of deer populations. An increased food supply from agriculture, irrigation, and exotic plants provide a food source for deer later in the season than formerly available. In some areas, dogs may discourage ungulate populations. Deer do not live on Trial Island and are rare on Alpha and Griffin Island.

Ungulates browsing on shrubs, formerly associated with frequent low-intensity fires, favours the persistence of meadow species. Shrubs that survive fire are browsed sufficiently to shift the competitive balance further in favour of meadow species. Tall, palatable forbs with elevated meristems (growing tips) suffer greatly from grazing. Unpalatable species, low-growing forbs and grasses (which do not have elevated meristems) gain a competitive advantage. Changing herbivory patterns may cause positive or negative effects to species at risk depending on the palatability of the species (or their foodplants) and the palatability of competing vegetation.

The effect of native invertebrate predators is not known. Insect seed predators, especially pre-dispersal seed predators that can destroy seed production from entire inflorescences, may seriously affect reproductive capabilities (Bigger 1999). Threat 11 discusses threats associated with livestock grazing.

1.6.15 Pesticides

Invasion by exotic gypsy moth has led to aerial spraying of Bacillus thuringiensis ssp. kurtaski(Btk) for control. Btk is lethal to most butterfly and moth larvae, and Taylor's checkerspot and island marble larvae are actively feeding during the early spring when Btk is likely scheduled for application (Wagner and Miller, 1995; Nealis pers. comm. 2003). Btk at toxic concentrations can drift for over two miles from target spray areas (Whaley et al. 1998). Refer to GOERT (2002) for approaches for dealing with this threat (p.36).

1.6.16 Cultivation of non-native plants

Cultivation of non-native plants (e.g. lawns and horticultural plants) adjacent to occurrences of species at risk may introduce new invasive species, increase herbicide use, alter moisture regimes, and decrease native foodplants for butterflies. Horticultural plants may also escape from cultivation and become naturalized further adding to the problem of invasive species. Planting and maintenance of lawns and ornamental horticultural plants next to occurrences of bear's-foot sanicle in Saxe Point Park may have eliminated suitable habitat for this species (Matt Fairbarns, pers. obs.).

1.6.17 Marine pollution

The Strait of Juan de Fuca is the most active shipping lane on the Pacific Coast north of San Francisco. The threat of oil tanker collisions and oil spills is prominent. In December 2003, a freighter was only 3 minutes of running aground on Trial Island (Victoria Times-Colonist 2003), a site for 5 of the 7 plant species in this strategy and one of the former locations for Taylor's checkerspot.

Much of the maritime meadow habitat occurs next to the intertidal zone and is affected by saltspray during storm events and may be vulnerable to marine pollution. More research is needed to determine the current and potential effects of diffuse marine pollution and a catastrophic point source spill on species at risk.

1.6.18 Invasive invertebrates

The effect on nutrient cycling and ecosystem productivity by introduced earthworms requires further research (Fuchs 2001). Likewise, the effect of herbivory by the introduced black slug (Arion rufus) and seed predation by introduced insects on the species addressed in this recovery strategy is not known.

1.6.19 Invasive alien invertebrates

There has been minimal research on the effect of introduced vertebrates on species at risk in Garry oak ecosystems (GOERT 2002). Rabbits (Sylvilagus floridanus and Oryctolagus cuniculus) and rats (Rattus sp.) are found in maritime meadows and likely eat vegetation and seeds. Introduced birds such as the European starling (Sturnus vulgaris) and house sparrow (Passer domesticus) feed on invertebrates and may affect butterflies at risk. The effect of opossums (Didelphis virginiana) in Garry oak ecosystems on Denman and Hornby Islands has not been investigated.