Multi-species management plan for Athabasca Sand Dunes 2013: chapter 2

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4. Threats

4.1 Threat Assessment

Threats are similar for all the species of special concern in the Athabasca Sand Dunes. Therefore, the threats are not presented separately by species.

^a Level of Concern – indicates whether the threat is an overall high, medium, or low concern for recovery of the species, taking into account extent, occurrence, frequency, severity, and causal certainty.
^b Extent – indicates whether the threat is widespread, localized, or unknown across the species range.
^cOccurrence – indicates whether the threat is historic (contributed to decline but no longer affecting the species), current (affecting the species now), imminent (is expected to affect the species very soon), anticipated (may affect the species in the future), or unknown.
^dFrequency – indicates whether the threat is a one-time occurrence, seasonal(either because the species is migratory or the threat only occurs at certain times of the year), continuous(on-going), recurrent (reoccurs from time to time but not on an annual or seasonal basis), or unknown.
^eSeverity – indicates whether the level of severity of the threat is high (very large population-level effect), medium, low, or unknown.
^f Causal Certainty – indicates whether the best available knowledge about the threat and its impact on population viability is high (evidence causally links the threat to stresses on population viability), medium(correlation between the threat and population viability, expert opinion, etc.), or low (assumed or plausible threat only).

4.2 Description of Threats

Acid Deposition

The impact of acid deposition in Canada has been thoroughly reviewed by the Meterological Service of Canada (MSC 2004). Most evidence of significant impacts on ecosystems comes from eastern Canada, where higher pollution levels coincide with large areas of sensitive ecosystems. However, increases in emissions of sulphur dioxide (SO₂) and nitrogen oxides (NO_x) from oil sands operations in the Fort McMurray, Alberta area, (about 300 km to the southwest), as well as other sources, are raising concerns that impacts could increase in the northern parts of the Prairie Provinces (Whitfield et al. 2010). Much of northern Saskatchewan is geologically sensitive to acid deposition, but MSC (2004) found that there is insufficient data on deposition rates and ecosystem sensitivity to evaluate impacts.

According to MSC (2004), the most important effect of acid deposition on terrestrial ecosystems is reduction in soil fertility because of leaching of base cations. Other indirect effects of soil acidification include increased plant uptake of metals such as iron and aluminum, which can reach toxic levels (MSC 2004). Direct effects of acid deposition on foliar surfaces are only evident at levels which are rarely found in Canadian environments (MSC 2004). Potential impacts are evaluated by determining whether levels of acid deposition exceed the critical load (i.e. the load below which there are no significant harmful effects to sensitive biological components). In soils, the critical load depends on the supply of base cations as well as other factors. The soils of the Precambrian Shield generally have low critical loads, meaning that they could be adversely affected by relatively low levels of acid deposition (MSC 2004). WBK and Associates (2006) presented maps of estimated acid deposition in the Prairie Provinces in 1995, 2000, and 2010 (projected). Acid deposition for sulfur and nitrogen was estimated to be relatively low in the Lake Athabasca area compared to many other regions in the Prairie Provinces. In spite of the fact that aerial deposition of base cations (which have a neutralizing effect) is also low, this area was mapped in the lowest class of potential acid input (acid deposition minus base deposition) in all three years: 0.00 – 0.10 keq H⁺/ha/yr, which is below the critical load estimated for sandy soils supporting jack pine forests in Alberta (Foster et al. 2001). WBK and Associates (2006) also compared acid input to soil-based critical load, for Alberta only. In the northeast corner of the province, adjacent to the Athabasca Sand Dunes in Saskatchewan, acid deposition was estimated to be 0-30% of the critical load in all three years. Similarly, Aherne (2008) found that most soil map units in Alberta had deposition below the critical load. However, Whitfield et al. (2010), using the most recent atmospheric deposition data and regionally calibrated rates of base-supply from weathering, found that several sites near the Athabasca Sand dunes already exceed the critical load. While the earlier results suggest that acid deposition is not high enough yet to cause concern, the more recent study indicates a significant impact on soils. Moreover, future expansion of oil sands operations will increase the downwind deposition of acids (Whitfield et al. 2010).

In the Fort McMurray, Alberta area, where acid deposition levels are considerably higher than they are further north, monitoring of vegetation plots showed no measurable effects on forest health (AGRA 1999, AMEC 2002, 2003). These plots were on sandy soils with low buffering capacity, as are the soils in the Athabasca Sand Dunes. Despite this research, the effects on the Athabasca endemic species in particular are not yet known. Preliminary investigations at the University of Saskatchewan suggest that root growth rates of Athabasca Thrift would be substantially impaired following germination on an acidified substrate (Lamb et al. 2011). Lamb et al. (2011) also suggested that acid deposition is likely to threaten Mackenzie Hairgrass, because it commonly germinates on open sand following precipitation events.

Climate Change

The most serious concern related to climate change is the effect on growing conditions for plants. Presumably the endemic plants are adapted to the prevailing range of temperatures and other climatic var.ables in the region. If the climate were to rapidly become much warmer, as is predicted, the endemics might find themselves increasingly maladapted. While this is a threat to a wide range of organisms, the Athabasca endemics may be particularly vulnerable because of low genetic diversity and restricted ranges. Two cases have been studied in which the sand dune endemics have less genetic diversity than their more widespread relatives: Felt-leaf Willow (Salix silicicola) vs. Alaska willow (S. alaxensis) (Purdy and Bayer 1995a), and Mackenzie Hairgrass (Deschampsia mackenzieana) vs. Tufted Hairgrass (D. cespitosa) (Purdy and Bayer 1995b. By contrast, Large-headed Woolly Yarrow (Achillea millefolium ssp. megacephala ) maintains more var.ability than its widespread relative, Common or Woolly Yarrow (A. millefolium ssp. lanulosa) (Purdy and Bayer 1996). Those species with reduced genetic diversity may have reduced capacity to shift their physiological tolerances to adapt to warmer climates. Small population size may further increase the vulnerability of these species to habitat change. Moreover, because their ranges are so restricted, there is no potential for northward migration of southern ecotypes that are already adapted to warmer climates, and there are few active dune habitats to the north to which the existing populations could migrate. A warming, drying climate trend could create more habitat if currently vegetated dune fields become active, but it could also reduce the already limited area of wet inter-dune slacks which are thought to be important for establishment of the endemics

Continuing gene flow with wide-ranging relatives could be one means by which the endemics could overcome this restriction. Gene flow is prevented between Felt-leaf Willow and Alaska Willow because their current ranges do not overlap, and between Mackenzie Hairgrass and Tufted Hairgrass because the former is a tetraploid (i.e. having four sets of chromosomes) that is reproductively isolated from its diploid (i.e. having two sets of chromosomes) progenitor (Purdy et al. 1994, Purdy and Bayer 1995a, 1995b).

Future climate change could alter the hydrology of Lake Athabasca and its connecting streams through effects on precipitation, snowmelt, or ice-damming of rivers during spring runoff (Leconte et al. 2006, Pietroniro et al. 2006, Toth et al. 2006) with possible effects on activity or stability of the dunes (see Altered Hydrology). However, the impact of these hydrological changes on the dune landscape will depend on their magnitude. When climatic scenarios for doubling of atmospheric CO₂ were applied to a hydrological model of the Peace-Athabasca system, the changes in the average level of Lake Athabasca were on the order of a few tens of centimetres, which would be unlikely to affect the amount of dune activity (Leconte et al. 2006, Pietroniro et al. 2006, Toth et al. 2006). Climate change could also alter wind patterns, which might change the dynamics of the dunes.

Recreational Activities and Other Human Disturbance

COSEWICassessments of the endemic species have emphasized the threat from physical habitat disturbance and trampling (Harms 1998, 1999a-e, Argus 1999a). Factors mentioned as contributing to this threat include:

• Increasing tourism, including ecotourism trips and canoe trips down the William and McFarlane Rivers with visitors camping in the Park and hiking on the dunes. Park regulations designate campsites and acceptable activities on the dunes, but the effectiveness of these regulations is unknown.
• Increasing research activities by scientists or park staff.
• All-terrain vehicle traffic by residents of the Lake Athabasca region, despite regulations against it, which may not be enforceable.
• Recreational boat traffic from the Fort McMurray area using the Athabasca River to access Lake Athabasca and the dunes (Bihun 1998).
• The winter road on the west side of the park, which provides snowmobile access from the Cluff Lake, Saskatchewan area, possibly leading to disturbance of the dunes or the endemic plants by snowmobile traffic. At one time there was also a concern that this route would be developed as an all-weather road, but the construction of the road from Points North to Stony Rapids, Saskatchewan makes another road to Lake Athabasca unlikely (Argus 1999a).
• Proximity of the general area to uranium mining in Saskatchewan. Geophysical surveys were done in the area in 1997-98 (Argus 1999a). If mining did become economically feasible, it could take place up to the edge of the Provincial Park, which borders the active dunes. The greatest concern with mine development would be increased visitor traffic to the dunes. However, in the case of an organized entity like a mine, it should be possible to restrict off-site travel by workers.
• Administrative inability to control access, even if regulations are in place, because of lack of staff or resources.
• Possible future loss of political will to protect the Park because of pressure from resource industry or tourism interests.
• Sensitivity to disturbance of the gravel pavements, on which tracks remain visible for years. Disturbance of the gravel veneer could increase the rate of surface erosion. This is the habitat most important for Athabasca Thrift.

However, the severity of the threat posed by recreational activities and other human disturbances may be moderated by two factors:

• The dunes are in an isolated location, with low visitation because access is difficult and expensive for most people. The 2009-2010 surveys found only three ATV tracks, which were relatively straight indicating an individual traveling to a destination rather than joyriding (Lamb et al. 2011). No impacts from camping or other activities were observed.
• The endemics are disturbance-adapted species. The dunes, which are their main habitat, are inherently unstable substrates which are constantly disturbed by natural wind erosion. Adaptation to this disturbed habitat is what differentiates the endemics from their wide-ranging relatives. In this context, the threat posed by visitor-induced disturbance is less than it would be for disturbance-sensitive species.

Invasive Alien Species

This is a possible threat, but one for which there is no evidence at present. One of the consequences of increased traffic into the Athabasca Sand Dunes could be the introduction of invasive alien plants. In many biomes, alien plants have become invasive in natural plant communities, crowding out the native species. However, the risk of significant invasion in the Athabasca Sand Dunes is unknown. In northern biomes, while alien weeds can be found in human-disturbed habitats such as roadsides, there appear to be few cases of invasion into natural communities (Mosquin 1997, Simberloff 2001, Sumners and Archibold 2007). Most invasives are intolerant of shade, so are more likely to appear in open habitats (including floodplains, burnovers, and cutovers) than in closed forests. Invasion of the Athabasca Sand Dunes would clearly not be limited by shade. In the prairies of southern Saskatchewan, the introduced forage grass Crested Wheatgrass (Agropyron cristatum) and the introduced invasive alien forb Leafy Spurge (Euphorbia esula) have invaded some active dunes and threatened to stabilize them (Godwin and Thorpe 2006). Over the long term, climate change could make invasions like this more likely in the north.

There are apparently no alien plant invasion problems in the Athabasca Sand Dunes at present (Lamb and Guedo 2012). The species list from the Saskatchewan Research Council (SRC) study of the dunes in the 1970s included Kentucky Bluegrass (Poa pratensis) (which could be of either native or alien origin) and the annual Lamb’s Quarters (Chenopodium album) (Abouguendia et al. 1981). Field surveys in 2009-2010 recorded no potentially invasive species either on the dunes or on the beaches of Lake Athabasca (Lamb and Guedo 2012). Additional alien plants recorded on disturbed sites in the Uranium City area on the north side of the lake include Smooth Brome-grass (Bromus inermis), White Sweet-clover (Melilotus alba), White and Alsike Clover (Trifoliumrepens, T. hybridum), Scentless Chamomile (Matricaria maritima), and Dandelion (Taraxacum officinale) (Harms 1982). ATV traffic is a possible vector for introduction of these invasive alien plants to the dunes because of seed-bearing mud on the tires of ATVs. Moist dune slacks are perhaps the most likely habitat for establishment of alien plants.

Seed Collection

According to Argus (1998a) there is an interest in using sand dune endemics for reclamation of oil sand operations. Companies have collected seed from the Park, a practice which Argus considered incompatible with protection of these species and is an illegal practice according to Saskatchewan’s “The Parks Act”. However, a factor that moderates this threat is that such collection is likely to involve small amounts of seed intended for propagation, not bulk quantities intended for direct use. Menges et al. (2004) suggested that 10% of the seed crop could be harvested once every 10 years to ensure at least a 95% probability of population persistence for most species of perennials.

Altered Hydrology

The threat posed to the Athabasca Sand Dunes by hydrological change was apparently one of the major concerns during the SRC study in the 1970s (Abouguendia et al. 1981). According to David (1981) the extent of active dunes in the Athabasca Sand Dunes is controlled by the height of the water table, because of the stabilizing effect of saturation with water. The water table is in turn affected by the height of Lake Athabasca, which is continuous with the shallow surface aquifer of the dunes. Therefore, rising lake levels would result in increased stabilization of dunes. The effect would be greatest in areas that already have a low proportion of active dunes because of shallow depth to the water table, whereas the large William River dunes would be little affected because of their high topographic position (David 1981). Rising water tables would flood dune slacks, increasing the proportions of hydric^[2] and mesic^[3] habitats and reducing xeric^[4] habitats (Abouguendia et al. 1981). Falling lake levels would result in gradually increasing dune activity (David 1981), which would increase the habitat for species of active dunes (Abouguendia et al. 1981). However, Argus (1998) pointed out that reducing the extent of wet dune slacks would also eliminate important seedbeds for the endemic plants. Abouguendia et al. (1981) suggested that the least favourable situation would be alternating high and low lake levels, which would cause unstable conditions leading to reduced vegetation cover and species diversity. Argus (1998) suggested that water control structures on the rivers feeding Lake Athabasca could have deleterious effects such as increasing shoreline erosion.

The level of Lake Athabasca is controlled by the complex hydrological relationships of the Peace-Athabasca Delta at the west end of the lake. If the level of the Peace River is low, Lake Athabasca drains freely into it, whereas if the river is high it impedes the outflow, resulting in high lake levels. Since 1968 the Peace River has been controlled by the Bennett Dam in northern British Columbia, and in the past this was suspected of causing a shift to low lake levels. However, a time series from 1934 to 1996 shows that maximum annual lake levels fluctuated from high to low (over a range of about 3 metres), both before and after construction of the dam (Prowse et al. 2006). If anything, the dam appears to have moderated these fluctuations somewhat (Prowse et al. 2006), reducing any concern about adverse affects of alternating high and low lake levels.

Over a longer time period, studies using paleolimnological methods have shown that Lake Athabasca was relatively low during the “Late Medieval Drought” from 1100 to 1600, relatively high during the “Little Ice Age” from 1600 to 1900, and declined again during the 20^th century (Wolfe et al. 2008, Sinnatamby et al. 2009). These authors argued that natural, climate-driven changes overwhelm any effect of dam construction on lake levels. The fact that the sand dune endemics have survived through naturally var.ing levels over the centuries tends to moderate concerns over any effects of water development.

5. Management Objective

The endemic plants of the Athabasca Dunes have small populations mainly because they are restricted to a habitat of small spatial extent. There is no evidence showing that these plants have declined in area of occupancy or population size. They are in a remote location with limited human impact, so are mainly affected by natural processes. While a number of threats have been identified, these are largely potential or speculative threats, with no concrete evidence that they are currently affecting populations of these species.

In this context, the management objective is to maintain the current population density (as indicated by the results in Table 3) and the current area of occupancy (as indicated by the results in Table 4) of each of the seven species of special concern. Achievement of this objective would be assessed by future resurvey of the same transects as used in the 2009-2010 survey, or a similar survey effort, with a statistically significant decrease in density or area of occupancy indicating that the objective had not been met.

6. Broad Strategies and Conservation Measures

6.1 Actions Already Completed or Underway

The main provincial action to protect these plants (as well as other ecosystem values) was the establishment of the ASDPP in 1992. This park encompasses almost the entire known ranges of the seven species of special concern. Within the Saskatchewan provincial park system, it is classified as a “wilderness park”, and is to be “used primarily for the preservation of natural landscapes in a natural state and the pursuit of outdoor recreational activities that are consistent with that use” (Bihun 1998, Parks Branch 1988). Endemic plants, along with other wildlife, inside the Park are protected under The Parks Regulations, 1991.

A draft management strategy was developed for ASDPP in the 1990s (Bihun 1998) and continues to be used by the Government of Saskatchewan to manage the Park. This strategy lists the endemic plants, as well as the active sand dunes, braided river channels, and desert pavements, as unique features which ASDPP was established to protect. The strategy outlines specific measures aimed at controlling visitor impacts and protecting against human-caused disturbances.

A quantitative survey of the Athabasca endemics was conducted in 2009-2010, by a cooperative effort among Saskatchewan Tourism, Parks, Culture and Sport, Saskatchewan Environment, Environment Canada, and the University of Saskatchewan. The results of this survey have been analyzed and reported by Lamb et al. (2011), and show locations where each species was observed as well as population density by habitat type. This survey provides an excellent foundation for future monitoring.

6.2 Broad Strategies

Strategy 1: Develop and implement a monitoring strategy to detect future changes in area of occupancy, population size, and threats from human disturbance, and invasive alien species. There is currently no information on trends in occupancy or population size of the Athabasca endemics.  The 2009-2010 survey (Lamb et al. 2011) provides baseline quantitative data, and will form the basis for development of a monitoring plan to detect changes from that baseline. 

Strategy 2: Fill in information gaps to broaden our knowledge of the ecology of these species, the biophysical features and geographic extent of their habitats and the severity and causal certainty posed by var.ous threats. Refer to to Lamb et al. (2011) for priorities for future research activities.

Strategy 3: Manage Athabasca Sand Dunes Provincial Park to maintain habitat for, and to conserve, these seven species. Reports on the Athabasca endemics have recommended conservation measures such as regulating and controlling movements of visitors, and prohibiting use of ATVs (Argus 1999a, Harms 1998, 1999a, 1999b, 1999c, 1999d, 1999e). Such measures are already included in the draft Park Management Strategy (Bihun 1998). In addition, the reports have recommended providing a buffer zone around the Park, particularly south of the William River dunes, to prevent mining or recreational developments (Argus 1999a, Harms 1998, 1999a-e), and the Athabasca Sand Dunes Provincial Park Management Strategy recommended increasing the size of the park for this purpose (Bihun 1998).

Strategy 4: Communicate acid deposition and climate change threats to policy-makers. These threats are beyond the control of the agencies responsible for managing species at risk. However, at higher levels in the government hierarchy, policies are being developed to address them. If research provides more specific evidence of threats to the Athabasca endemics from these causes, then this information may inform policy-makers and should be communicated to them.

Strategy 5: Conduct public outreach with local residents, visitor groups, and the general public regarding the species of special concern. There is a need for public education on the Athabasca Sand Dune endemics, particularly among local people in the Lake Athabasca area, tourists and ecotour operators. It is unlikely that protection of these species can be achieved by enforcement alone, given the limited government resources in the area. This makes it especially important that local people be convinced of the need to protect the species and their habitat, and for outside users, including researchers, ecotourists and canoe trippers, to understand the value of the species and the sensitive habitat (particularly the desert pavements) and their potential impact even during a short period.

6.3 Conservation Measures

7. Measuring Progress

The performance indicator presented below will provide a way to define and measure progress towards the achievement of the management objective. Success in implementing this management plan will be evaluated every five years on the basis of the following performance indicator:

• the current population density and area of occupancy are maintained for each of the seven species of special concern.