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Boreal Felt Lichen, Atlantic Population

Background

1.1   Species Assessment Information from COSEWIC

Date of Assessment: May 2002

Common Name: Boreal felt lichen (Atlantic population)

Scientific Name: Erioderma pedicellatum

COSEWIC Status: Endangered

Reason for Designation: A population restricted to regions with a cool, humid, oceanic climate, highly sensitive to atmospheric pollutants such as acid precipitation. It has experienced a dramatic decline of over 90% in occurrences and individuals over the last two decades due, in particular, to air pollution and other sources of habitat loss and/or degradation. Extirpation of the few remaining individuals at three sites is imminent.

Canadian Occurrence: New Brunswick, Nova Scotia

COSEWIC Status History: Designated Endangered in May 2002. Assessment based on a new status report.

1.2   Description

1.2.1      Description of the species

Lichens are distinct symbiotic organisms made up from the association of microscopic algae or cyanobacteria and filamentous fungi. Boreal felt lichen (Erioderma pedicellatum) is a foliose cyanolichen, with distinctive upturned edges that reveal white undersides. The range of colour of the lichen is determined by the hydration of the lichen body called the thallus. It appears bluish grey when moist and dark grey to greyish brown when dry. Boreal felt lichen most commonly measures 2–5 cm in diameter, although it can be up to 12 cm in diameter. This lichen has a generation time of approximately 30 years. Boreal felt lichen is vulnerable to atmospheric pollution. The habitat for boreal felt lichen occurs in cool, moist, maritime climates. New evidence suggests that the genus may be among the oldest of foliose lichens, perhaps well over 400 million years old (Maass and Yetman 2002).

Special significance

Boreal felt lichen has been coined the “panda bear” of the lichens, acting as a symbol of the immediate and very real threat to the world’s boreal forests (Maass and Yetman 2002). The ability of this species to indicate fluctuations in local air quality makes it valuable as an environmental indicator. Boreal felt lichen appears to have a unique and complex relationship with the liverwort Frullania tamarisci ssp. asagrayana (discussed in section 1.2.2), which scientists are only beginning to understand.

Global status 

·       IUCN (International Union for Conservation of Nature and Natural Resources) Red List of Threatened Species: Critically Endangered (Scheidegger 2003)

·       NatureServe Global Conservation Status Rank: G1G2Q (Critically Imperiled/ Imperiled; Q = questionable taxonomy) [1]

·       Rounded global status[2]: G1 (Critically Imperiled)

Provincial status

·       New Brunswick: None

·       Newfoundland and Labrador: Vulnerable (boreal population)

·       Nova Scotia: Endangered 

Populations and distribution

There are two Canadian populations of boreal felt lichen: the boreal population (Newfoundland and Labrador) and the Atlantic population (Nova Scotia and New Brunswick). The 2002 Committee on the Status of Endangered Wildlife in Canada (COSEWIC) Status Report for boreal felt lichen attributes the distinction to “the fact that they occur in different ecological regions and are subject to different degrees of risk” (Maass and Yetman 2002: p. vii). The Atlantic population is currently found only in Nova Scotia and is believed to be extirpated from New Brunswick.

Boreal population of boreal felt lichen

COSEWIC lists the boreal population of boreal felt lichen as a species of Special Concern, although it is the largest and healthiest known population in the world. Newfoundland and Labrador’s population is found mainly in the Avalon Forest and Maritime Barrens ecoregions in the southern half of the island of Newfoundland. The Newfoundland and Labrador Department of Environment and Conservation (2006) is currently preparing a draft management plan for the boreal population of boreal felt lichen. Although the boreal population faces a different degree of vulnerability to threats compared with the Atlantic population, this recovery strategy will provide a valuable tool for recovery planning for both populations.

This document and the recovery strategies discussed within it pertain to the Atlantic population of boreal felt lichen. For more information about the boreal population, consult the COSEWIC Status Report on boreal felt lichen (Maass and Yetman 2002) or visit www.sararegistry.gc.ca/.

Historic distribution of the global population of boreal felt lichen

The first recorded collection of boreal felt lichen occurred in 1902 on Campobello Island, New Brunswick, while the second record of boreal felt lichen was from Norway in 1938 (Clayden 1997). Boreal felt lichen has likely been extirpated from Sweden and Norway (Goward et al. 1998). Significant efforts by researcher Wolfgang Maass yielded numerous new sites in both Nova Scotia and Newfoundland and Labrador (boreal population) during the 1980s.

Historic distribution of the Atlantic population of boreal felt lichen

Maass and Yetman (2002) recorded 46 sites with a total of 169 boreal felt lichen thalli in Nova Scotia between 1980 and 1995 (Figure 1). Surveying from 1995 to 2002 resulted in the location of only 13 boreal felt lichen thalli at 3 of the original 46 sites, suggesting a population decline (Maass and Yetman 2002). By March 2006, only one of the original sites supported boreal felt lichen.

Although the earliest recorded collection of boreal felt lichen in Canada was from New Brunswick, it is the only observation of the species in the province (Clayden 1997). Moreover, the possibility of finding new occurrences of boreal felt lichen in New Brunswick is believed to be low, given the apparent absence of indicator or associated cyanolichen species on conifers along the Bay of Fundy coast (New Brunswick Department of Natural Resources 2006). The Recovery Team is prepared to initiate recovery actions if there are reports of boreal felt lichen or its indicator species in the province.

Current distribution of the Atlantic population of boreal felt lichen

The only known extant sites of the Atlantic population of boreal felt lichen occur in Nova Scotia. As of March 2006, only 1 of the 46 Nova Scotia locations of boreal felt lichen identified by Maass and Yetman (2002) retained the lichen, but 8 new locations (all unknown when the 2002 COSEWIC Status Report was written) have been identified using habitat suitability maps and systematic surveying (Figure 2; Cameron and Neily 2006).

Figure 1. Distribution of the Atlantic population of boreal felt lichen prior to 1995 (from Maass and Yetman 2002).

Figure 1. Distribution of the Atlantic population of boreal felt lichen prior to 1995

Figure 2. Distribution of the Atlantic population of boreal felt lichen as of March 2006 (Nova Scotia Department of Environment and Labour, unpublished data).

Figure 2. Distribution of the Atlantic population of boreal felt lichen as of March 2006

1.2.2      Description of the biological needs of the species

Biological needs, ecological role, and limiting factors

Life cycle

The life cycle of boreal felt lichen is not yet completely understood. In 1996, Christoph Scheidegger hypothesized that the life cycle of boreal felt lichen was linked to the ecological cycle of balsam fir (Abies balsamea) habitat (Clayden 1997; Maass and Yetman 2002). His hypotheses were that there is only one generation of Erioderma thalli per successional cycle of the balsam fir stand; that the growth rate of boreal felt lichen accelerates during the overmature to decaying phase of the forest (a phase lasting approximately 15–25 years) as a result of advantageous light conditions created by canopy gaps left by dead and decaying trees; that the lichen then releases spores to adjacent younger fir stands; and that a new cycle of boreal felt lichen begins within a few hundred metres of the initial population.

Reproduction and symbiosis 

Lichens are formed by the association of a fungus with a bacterium. The bacterium is responsible for producing food for the organism through photosynthesis (Brodo et al. 2001). Boreal felt lichen is a cyanolichen, which means that its photosynthetic partner, or photobiont, is a cyanobacterium. Scytonema is the cyanobacterium associated with boreal felt lichen. Lichens are named for the mycobiont, the fungal partner, so Erioderma pedicellatum is the name that represents both the fungal partner and the lichen. Reproduction of the lichen is achieved sexually, initiated by the chance contact between a group of fungal spores and a strand of Scytonema (Maass and Yetman 2002).

While Scytonema can grow and reproduce independently, there is no evidence that the mycobiont, Erioderma pedicellatum, grows independently (R. Cameron pers. comm. 2006). If the mycobiont does grow independently, it would be theoretically possible for the lichen to regenerate spontaneously after being absent for a period of time, but only if there are Erioderma pedicellatum spores available (R. Cameron pers. comm. 2006). Erioderma pedicellatum produces spores only when in partnership with Scytonema (R. Cameron pers. comm. 2006).  The symbiosis between the photobiont and the mycobiont is complex; owing to the energy consumed by the initial joining of the partners, it is expected that the initial rate of growth is slower than when the lichen becomes visible at 2–3 mm in diameter. Preliminary results of linear growth rate investigations suggest that it takes 7–13 years for thalli to reach maturity once established, but these results are based on only 11 thalli (Cameron and Neily 2006). A more precise understanding of growth rate should emerge with more research.

An intriguing aspect of boreal felt lichen is its relationship with a liverwort, Frullania tamarisci ssp. asagrayana. The co-occurrence of boreal felt lichen and Frullania, coupled with the known occurrence of Scytonema within the water sacs of Frullania, has led some to suggest that the moisture-rich water sacs of Frullania act as a nursery to the lichenization of boreal felt lichen (Scheidegger 1996; Maass and Yetman 2002).

Limiting factors

Boreal felt lichen is biologically limited by the following factors: its globally limited distribution and small population size; its relationship with Frullania tamarisci ssp. asagrayana; its requirement for bark substrates of a specific acidity; the nature of its life cycle (boreal felt lichen does not produce any type of joint fungal–bacterial propagule; therefore, it must reestablish itself each generation from its separate components); and its apparent hypersensitivity to acidification of its substrates and/or to direct adverse effects of air pollutants such as nitrogen oxides and sulphur dioxide. It is necessary to determine whether or not the quality or quantity of forest habitat available is inherently limiting to boreal felt lichen recovery. 

Habitat needs

Boreal felt lichen is relatively specialized in its habitat requirements. Thalli are typically found on north-facing trunks of mature and overmature balsam fir trees (Maass and Yetman 2002; Richardson and Cameron 2004). Suitability of the habitat for occupation by the lichen may be increased if the forest is located on slopes with northern or northeastern exposure. The high relative humidity of these habitats may also be suitable for growth of companion indicator species of beard and hair lichens, such as Usnea species, Alectoria sarmentosa, andBryoria species (S.R. Clayden pers. comm. 2006). Other characteristics of known sites include cool, moist habitat conditions that remain relatively constant throughout the year, such as those adjacent to Sphagnum-rich wetlands that can maintain moisture levels during periods of drought (Maass and Yetman 2002). In Nova Scotia, boreal felt lichen has occasionally been found living on white spruce (Picea glauca) and red maple (Acer rubrum) substrates in mixedwood stands (Maass and Yetman 2002).

Limited observations suggest that boreal felt lichen most often occurs within 25 km of the sea coast at an elevation up to 500 m above sea level. Forest habitat is described by researchers as having low open crown closure due to natural forest dynamics. Many factors that affect the suitability of habitat for boreal felt lichen are not precisely known, including the temperatures and level of humidity that must be maintained within the habitat and the levels to which the lichen can withstand pollutants such as sulphur dioxide and nitrogen oxides. Regardless, clean air and clean water sources are considered important aspects of boreal felt lichen habitat. Thus, there is some critical but as yet undetermined distance surrounding boreal felt lichen habitat that is essential to the lichen’s survival. Structural and functional features of forest habitat believed to be important include moisture retention, forest integrity (total cover, degree of fragmentation or patch continuity, age, composition, etc.), protection from weather events that may cause blowdowns, and the ability to intercept some local air pollution.

Indicator species 

Coccocarpia palmicola and Lobaria scrobiculata (also cyanolichens) usually occur with boreal felt lichen and may be used as indicator species (Cameron and Richardson 2006).

1.3   Threats

Boreal felt lichen is cryptic and difficult to identify. The species lacks charisma, and there is still much unknown about the species and its habitat. Although these threats may be reduced somewhat through education and research, they contribute to the lichen’s vulnerability to physical threats. Physical threats to boreal felt lichen and its habitat are discussed below.

1.3.1   Acid precipitation/air pollution

Acid precipitation is destructive to boreal felt lichen in two ways: it causes immediate damage to the thallus through the uptake of air pollutants (cyanolichens’ nitrogen-fixing enzyme is known to be intolerant of sulphur dioxide), the suggested cause of damage to the holdfast mechanism (observed by W. Maass); and it further acidifies the naturally acidic substrates on which the lichen lives, thereby reducing the buffering capacity of the lichen (Maass and Yetman 2002).

The decline in lichen populations has been documented to have occurred in the 1980s (Maass and Yetman 2002), despite the fact that emissions of sulphur dioxide in Canada and the United States actually decreased over this time due to government actions to reduce acid rain (Environment Canada 2004a). This raises the possibility that the lichen or its associated species are also being impacted by other air pollutants, such as nitrogen oxides (T. Inkpen pers. comm. 2006).

The amount of acid deposition that an area can tolerate is known as its critical load. It is calculated as acid equivalents per hectare per year (eq/ha per year). Most of Nova Scotia is highly or extremely acid sensitive (Figure 3). Airflow dynamics carry air pollutants originating from cities such as Boston and New York along the northeast Atlantic coast, as well as pollutants from coal-burning electricity generating stations in the midwestern United States. These pollutants, in addition to local pollution sources, result in acidified precipitation (Beattie et al. 2002; Richardson and Cameron 2004). Acid fog is created by the collision between the cold air masses over the Gulf of Maine and the Bay of Fundy and the warm, humid, pollutant-bearing air masses coming upward along the Atlantic coast (Cox et al. 1989). Investigation is required to pinpoint local sources.

Figure 3. Critical load exceedance for forest soils in eastern Canada(no harvesting scenario).

Figure 3. Critical load exceedance for forest soils in eastern Canada

Boreal felt lichen populations in Nova Scotia occur in coastal areas subject to extended periods of acid fog, which increases the severity of the threat of acid precipitation to the lichen. The disappearance of boreal felt lichen from New Brunswick has been attributed to the impacts of acid precipitation (New Brunswick Department of Natural Resources 2006).

Initiatives to reduce acid precipitation are already in place through international actions under the Canada–United States Air Quality Agreement and domestic actions under the Canada-wide Acid Rain Strategy for Post-2000 (both documents available at www.ec.gc.ca). It is a recovery priority to better understand the impact of air pollution and acid precipitation on boreal felt lichen. Specific actions to help mitigate this threat are described in more detail in the Recovery section (section 2) and include identifying sources of air pollution and the lichen’s sensitivity to specific pollutants; identifying both local and transboundary sources to determine their relative threats; determining practices to mitigate human disturbances in and surrounding boreal felt lichen habitat; monitoring threats (e.g., acid deposition); and alerting those implementing pollution reduction programs to boreal felt lichen so the species may be used to support their programs.

1.3.2   Forestmanagement

Besides acid precipitation, forest practices are considered the other major threat to the Atlantic population of boreal felt lichen. Forest practices may cause fragmentation, alter the age structure, and simplify the biodiversity of forest stands. In Nova Scotia, even-aged management for spruce-dominated forest stands predominates (Canadian Council of Forest Ministers 2005). Entire locations of boreal felt lichen may be destroyed by large-scale clearcutting, particularly if the presence of boreal felt lichen has not been identified.

The effect of forest fragmentation on epiphytic lichens has been the subject of much work (Esseen and Renhorn 1998; Rheault et al. 2003; Pykala 2004; Richardson and Cameron 2004). When lichens are suddenly at the edge of a forest or in a fragmented forest, there is a reduction in dispersal ability and opportunity to recolonize in cutover areas (Rheault et al. 2003). Large-scale logging also greatly reduces the ability of a forest stand to buffer against times of low humidity (Maass and Yetman 2002). Some researchers suggest that this was the cause of boreal felt lichen extirpation from Vãrmland, Sweden, where logging took place in the immediate vicinity of the park where boreal felt lichen thalli were known to occur (Maass and Yetman 2002).

In 2005, at the oldest known boreal felt lichen site in Nova Scotia, a lone thallus on the west side of the site was lost to a blowdown (Cameron and Neily 2006). Although blowdowns are not an infrequent event, an adjacent clearcut (estimated to have occurred in 2000 or 2001) likely increased the vulnerability of this site to blowdowns and drought.

In Nova Scotia, harvested stands are usually replanted with unsuitable phorophytes that have more acidic bark than balsam fir, such as black spruce (Picea mariana), white spruce, red spruce, and Norway spruce (Picea abies) (Canadian Council of Forest Ministers 2005). Even-aged tree plantations are also not favourable to the establishment of new colonies of Scytonema, Frullania, or juvenile boreal felt lichen because of their low light conditions (Maass and Yetman 2002).

Communication and information sharing with the forestry industry in Nova Scotia are keystones to recovery efforts. Efforts made to alleviate the threat posed to boreal felt lichen by forestry management will be outlined in greater detail in the Recovery section (section 2) and include reviewing literature and best management practices for forest management as they pertain to boreal felt lichen; communicating with stakeholders to develop practical forest practices and recommendations for areas surrounding the lichen and its potential habitats; developing a voluntary stewardship agreement for use with landowners; and offering training to volunteers and foresters to identify boreal felt lichen and potential habitat.

1.3.3   Pestcontrol and the use of harmful aerial sprays

The COSEWIC Status Report for boreal felt lichen outlines the threat posed to a boreal population colony by trichlorfon, a spray reagent approved and considered to eliminate the yellow-headed spruce sawfly (Pikonema alaskensis) in 1998 (Maass and Yetman 2002). Because the thallus of boreal felt lichen does not repel water well, the liquid chemical is able to access and damage the cellular membranes of the lichen (Maass and Yetman 2002). Although a far less harmful agent was chosen (azadirachtin, an extract from the Indian neem tree (Azadirachta indica)), Maass and Yetman (2002) suggested that trichlorfon would most likely have decimated the area colonies.

There are no records of either of these agents being used in Nova Scotia (W. Fanning, NSDNR, pers. comm. 2006), but trichlorfon was used in New Brunswick in the 1970s (Mitchell and Roberts 1984). The most recent record of its use in New Brunswick was in a small-scale experiment in 1996 (N. E. Carter, NBDNR, pers. comm. 2006). Both provinces scrutinize all decisions surrounding the use of aerial sprays.

It is often difficult to predict the relative threats to boreal felt lichen of the aerial spray and the pest itself, and every situation may be different (Maass and Yetman 2002). Awareness of any potential pests in the vicinity of boreal felt lichen sites and participating in consultations to deal with such pests will ensure that boreal felt lichen will be considered when deciding whether, where, and what to spray. Environmental protection agencies must be informed of boreal felt lichen’s presence so it will be protected from such threats.

1.3.4   Climate: Droughts, hurricanes, forest fires, global warming

Based on field observations, boreal felt lichen cannot endure the desiccation that accompanies extreme weather events such as droughts and hurricanes (Maass and Yetman 2002). A severe storm in Guysborough County, Nova Scotia, created a windfall that destroyed one of the boreal felt lichen populations discovered in the 1980s (Maass and Yetman 2002).  

Forest fires may directly destroy boreal felt lichen, and they may also have indirect effects, because nitrogen-fixing lichens (including all cyanolichens) downwind of forest fire smoke can be destroyed by the small concentration of sulphur dioxide contained in the smoke (Maass and Yetman 2002).

Although it is difficult to quantify the effects of global warming on lichens, it is expected that they include reductions in range distributions (Maass and Yetman 2002). Lichens with affinities to particular tree species and lichens that require cool, moist habitats, such as boreal felt lichen, may be particularly sensitive to climate change (Maass and Yetman 2002).

Climatic changes are occurring, and boreal felt lichen may be susceptible to damage from these threats. The best protection against climatic threats that can be offered is to maintain a protective area around lichen sites and to monitor the effects of these events to guide future management decisions. To reduce the impact of climatic threats to boreal felt lichen, human disturbances in and surrounding boreal felt lichen habitat must be mitigated.

1.3.5   Effects of herbivory on the growth of balsam fir seedlings

The 2002 COSEWIC Status Report for boreal felt lichen (Maass and Yetman 2002) discusses the effects of moose browsing on balsam fir, but all observations were reported from Newfoundland and Labrador. In the vicinity of the known Atlantic population locations, there are no recorded observations of moose browsing on balsam fir seedlings. Moose are present throughout both New Brunswick and Nova Scotia, but the mainland population of moose in Nova Scotia is provincially endangered. Any measures to protect boreal felt lichen must carefully consider implications for moose recovery on mainland Nova Scotia. At present, it will be adequate to monitor lichen sites for evidence of herbivory.

1.3.6    Microfauna herbivory

The COSEWIC Status Report for boreal felt lichen recorded that mites and snails have both been observed browsing on boreal felt lichen, and it suggests that they pose only a very minor threat to boreal felt lichen populations (Maass and Yetman 2002). When the Lower Meaghers Grant site was visited in 2004, a boreal felt lichen thallus at the site was being heavily grazed by gastropods (Cameron and Neily 2006). A collected specimen was later identified as Arion subfuscus, a non-native introduction from Europe (Cameron and Neily 2006). It is not clear whether this single instance could be considered a population-level threat. Any additional observations of grazing will be recorded and assessed for evidence that such grazing requires further study or action.

1.3.7    Land development

The development of land for activities such as industry, residences, forestry, and agriculture creates disturbance and landscape alterations and also provides access to remote areas for people (Maass and Yetman 2002). The level of threat to boreal felt lichen from land development fluctuates as new sites are discovered and accessibility to sites changes. Boreal felt lichen habitat is protected by the federal Species at Risk Act and the Nova Scotia Endangered Species Act (NSESA). Specific actions to mitigate this threat include the identification of critical habitat, education, and voluntary stewardship agreements.

1.4   Knowledge Gaps

Knowledge gaps for boreal felt lichen include detailed information on its life cycle, growth rate, life history, genetic diversity, population dynamics, minimum viable population size, sensitivity to individual air pollutants and acid deposition, and sensitivity to specific forest practices. Critical habitat and the importance of unoccupied potential habitat must also be determined. The characteristics and quality of habitat required by boreal felt lichen and the relevant scale of threats to its habitat are not known; it is also not known how these threats to its habitat limit the species’ ability to recover.




[1]For more information see www.natureserve.org

[2]This value uses an algorithm to evaluate Conservation Status Ranks and systematically produces easier to interpret values without qualifiers or ranges (e.g. G1G2 becomes G1)