G.G.E. Scudder and I.M. Smith. 1998. Introduction and Summary in Smith, I.M., and G.G.E. Scudder, eds. Assessment of species diversity in the Montane Cordillera Ecozone. Burlington: Ecological Monitoring and Assessment Network, 1998.

INTRODUCTION AND SUMMARY

G.G.E. Scudder
Department of Zoology
University of British Columbia
Vancouver, B.C.
V6T IZ4
and
I.M. Smith
Biological Resources Program
Agriculture and Agri-food Canada
Central Experimental Farm
Ottawa, Ontario
K1A 0C6

INTRODUCTION

PREVIEW

The purpose of this report is to present the results of a series of investigations of the status and dynamics of species diversity and biogeography for selected taxa belonging to some of the major phylogenetic groups in the Montane Cordillera Ecozone. We include diverse taxa of fungi, cryptograms, vascular plants, arthropods and vertebrates whose species represent a wide range of structural and functional roles within the ecosystems of the Ecozone. We have recruited experts to summarize available information on the status of species diversity for each taxon and to assess the factors influencing changes in distributions and community composition in the Montane Cordillera from the end of the Wisconsinan Glacial Maximum to the present. Our synthesis of the resulting information and interpretations is aimed at strengthening the knowledge base for analyzing the dynamics of species level biodiversity in the Montane Cordillera. Our ultimate goal is to improve understanding of the relationship between species diversity in the Ecozone and the capacity of biological communities there to self-organize, self-regulate and adapt to human intervention.

The Montane Cordillera Ecozone extends from the eastern Rocky Mountains in Alberta to the western slope of the Cascades in British Columbia, and from the latitude of the Skeena Mountains in northern British Columbia to the United States border. It is Canada’s sixth largest ecozone, covering more than 49 million hectares. The Montane Cordillera is probably our most complex ecozone, with landscapes ranging from alpine tundra to dense coniferous forests, grasslands, riparian woodlands, dry sagebrush and Canada's only true desert, reflecting the exceptional diversity of topography and climate.

Modern species and community biodiversity in the Montane Cordillera developed through a complex process of recolonization by plants and animals following the retreat of the Cordilleran Ice Sheet beginning about 12000 years ago. Post-glacial repopulation apparently began somewhat earlier in this Ecozone than in more eastern parts of Canada. Cold-adapted species from periglacial refugia invaded first, followed by warmer-adapted species moving north along river valleys and intermontane trenches. Invasion of the Ecozone by plants and animals from peripheral refugia was episodal and correlated with climatic fluctuations throughout the Holocene.

14000 bp:      12000 bp:      10000 bp:  

During the historic period, tundra and taiga habitats have been restricted to high elevations, coniferous forests have dominated the lower slopes of mountain ranges, and grasslands and riparian woodlands have occupied intermontane plateaus and valleys. Extensive watersheds have developed throughout the Ecozone including more than 11000 lakes, 7 major river systems, and countless mountain streams, ponds and springs. Species arriving from neighbouring ecozones progressively enriched the diversity of Montane Cordillera communities, many of which comprise species assemblages that occur together nowhere else. Several of the taxonomic groups considered in this study have more species represented in the Montane Cordillera than in any other Canadian Ecozone, and all include species reported from Canada only in this Ecozone.

Evidence from paleontological and anthropological studies shows clearly that humans have interacted with other species in the Montane Cordillera throughout the postglacial period. Human hunters may have influenced the decline of some of the large mammals that disappeared from the Ecozone and certain plants and animals associated with human settlements were introduced and dispersed during the Holocene. The effects of human activities on species diversity increased following the arrival of Europeans during the seventeenth century. Early exploration and settlement of the Montane Cordillera during the eighteenth and nineteenth centuries was largely in response to the search for animal pelts, with well documented impact on populations of large, fur-bearing mammals. Human impacts have accelerated dramatically during the twentieth century. Old growth forests have been transformed into intensively managed stands, native grasslands have been extensively grazed or overgrazed, fertile bench lands and valley bottoms have been irrigated and converted to orchards and vineyards and transportation corridors have proliferated. Aquatic habitats have been dammed, diverted and channelized, degraded by riparian deforestation and agricultural run-off and polluted by industrial and municipal wastes. Transformation of landscapes and watersheds for agricultural, forestry, mining, hydroelectric, recreational and urban development has strongly and indiscriminately influenced the distributions and abundance of many species, resulting in reductions of native biota and introduction and spread of many exotics. As in the case of the Mixedwood Plains, recent human activities in the Montane Cordillera have resulted in a substantial increase in the both the total number of species inhabiting the Ecozone and the risk that many native species will be extirpated.

About 90% of the area of the Montane Cordillera Ecozone is in the province of British Columbia and the remaining 10% in western Alberta (Lowe et al. 1996). Some 70% of the area is forested, about 27% non-forested, and 3% is covered with water. The majority (92%) of the forested area is in timber productive forest, mostly of the softwood type.

The Ecozone comprises two ecodivisions, four ecoprovinces, 17 ecoregions and 59 ecodistricts (ecosections) (Ecological Stratification Working Group 1996) as summarized in Table 1. For the most part, it is rugged and mountainous in the south and east, and incorporates a major interior plateau to the west (Fig. 2). This plateau, largely consisting of the Nechako-Fraser-Thompson Plateaus, extends through the centre of British Columbia. It attains a maximum width of about 300 km at latitude 54° N, and a maximum length of about 650 km from near the 49th parallel to the Peace River reservoir (Farley 1979). Lying at an average elevation of 600-1200 m, the plateau consists of rolling upland, dotted with lakes, and mantled with varying thickness of glacial deposits.

The eastern mountainous system consists of several ranges separated by valleys. It encompasses two distinct physiographic regions, the Columbia Mountains plus Rocky Mountain Trench, and the eastern Rocky Mountains plus the Rocky Mountain Foothills. The highest elevations generally occur in the south, where summits may reach 3300 m above sea level. Examples include Mt. Assiniboine at 3618 m, Mt. Columbia at 3747 m and Mt. Robson at 3954 m.

Between latitudes 54° N and 56° N, the topography is more subdued, and even the higher peaks are generally less than 2100 m. Although most major river valleys run in a north-south direction, the mountain ranges of the eastern system are broken by several passes. The major ones, used by both rail and road are the Crowsnest Pass at 1357 m, the Kickinghorse Pass at 1622 m, the Rogers Pass at 1323 m, and the Yellowhead Pass at 1131 m.

Such a complex topography, results in large differences in temperature and precipitation across the Ecozone. The plateau area through the centre of British Columbia, being in the rain-shadow of the Coast Mountains, has a mean annual precipitation in some areas less than 30 cm. However in the Selkirk Mountains mean annual precipitation is 250-350 cm in some areas, with 150-250 cm in much of the Rocky Mountains.

Most of interior British Columbia is strongly influenced by both continental and maritime air, the latter being more prevalent in the south. In consequence, the southern interior valleys experience winter temperatures much less rigorous than those in the north. The warmest summer temperatures are recorded in the southern interior valleys, where, in the extreme South Okanagan, the mean daily temperature in July is over 22° C.

The complex topography and climate is reflected in the vegetation. The biogeoclimatic ecosystem classification system in British Columbia results from a synthesis of vegetation, climate and soil data (Pojar et al. 1987). Fourteen distinct biogeoclimatic zones are now recognized in the province (Meidinger and Pojar 1991), 13 of which are represented in the Montane Cordillera ecozone.

ALPINE TUNDRA. Essentially a treeless region characterized by harsh climate and occurring on the high mountains. The long, cold winters and short, cool growing seasons create conditions too severe for the growth of most woody plant, except in dwarf form. Hence this zone is dominated by dwarf shrubs, herbs, mosses and lichens. Owing to the severe climate, this zone is extremely sensitive to disturbance, the disturbed landscapes requiring decades or even centuries to recover to their natural states.

SPRUCE-WILLOW-BIRCH. This is a subalpine zone occurring in the severe climate in the north of the Ecozone. It occurs below the alpine tundra but above the boreal forest zones. At lower elevations, the zone is characterized by open forests of primarily white spruce and subalpine fir. Upper elevations are dominated by deciduous shrubs, including scrub birch and willow.

BOREAL WHITE AND BLACK SPRUCE. An extension of the extensive Belt of coniferous forest occurring across Canada, this zone occupies the valleys in the northern part of the Ecozone. Winters are long and cold and the growing season short, with the ground remaining frozen for much of the year. Where flat, the landscape is typically a mosaic of black spruce bogs, and white spruce and trembling aspen stands.

SUB-BOREAL PINE SPRUCE. This zone occurs on the high plateau of the west central interior of British Columbia, in the rain shadow of the Coast Mountains. The zone is characterized by many even-aged lodgepole pine stands, the result of an extensive fire history. A minor amount of white spruce regeneration occurs. Lichens and/or feathermosses usually dominate the understory. Pinegrass and kinnikinnick are also common.

SUB-BOREAL SPRUCE. This zone occurs in the central interior of British Columbia on gently rolling plateaus. Although the climate is severe, the winters are shorter and the growing season longer than in the boreal zones. Hybrid Engelmann-White spruce and subalpine fir are the dominant trees, although there are extensive stands of lodgepole pine In the drier parts of the zone, the result of numerous past fires. Wetlands are abundant dotting the landscape in poorly drained areas.

MOUNTAIN HEMLOCK. This is a subalpine zone occurring at high elevations on the coast. The growing season is short and the annual snowfall is high. Trees are absent where the snow pack remains late in the spring, or where the ground freezes under the snow. In the upper elevations forests thin out into open parkland, where trees are clumped and interspersed with sedge or mountain-heather communities. At lower elevations, the forest is continuous with Mountain hemlock and amabilis fir the dominant species.

ENGELMANN SPRUCE-SUBALPINE FIR. This is a subalpine zone, occurring at high elevations throughout much of the interior of British Columbia. The climate is severe, with short cool growing seasons and long cold winters. Only those trees capable of tolerating extended periods of frozen ground occur in this zone. The landscape at upper elevations is an open parkland, with trees clumped and interspersed with meadow, heath and grassland. Engelmann spruce, subalpine fir, and lodgepole pine are the dominant trees. Rhododendron and false azaleas are common understory shrubs. In wetter areas, where snowfall is more abundant, mountain hemlock occurs.

MONTANE SPRUCE. This zone occurs in the south central interior of British Columbia at middle elevations, and is most extensive on plateau areas. Winters are cold and summers moderately short and warm. Engelmann and hybrid spruce, and varying amounts of subalpine fir, are the characteristic tree species. Owing to past wildfires, successional forests of lodgepole pine, Douglas-fir and trembling aspen are common.

BUNCHGRASS. This grassland zone is confined to the lower elevations of the driest and hottest valleys of the southern interior of British Columbia. Bluebunch wheatgrass is the dominant bunchgrass on disturbed sites. At the lower elevations big sagebunch is common, particularly on overgrazed areas. Ponderosa pine and Douglas-fir occasionally occur in draws and on coarse textured soils, although the dry climate restricts their growth.

PONDEROSA PINE. This is the warmest and driest forest zone, confined to a narrow band in the driest and warmest valleys of the southern interior of British Columbia. It often borders the Bunchgrass Zone along its lower or drier limits. Ponderosa pine is the dominant tree, which requires frequent ground fires for its survival. Douglas-fir is common on the colder and moister sites. Where not overgrazed, the understory includes abundant grasses such as Bluebunch wheatgrass and rough fescue.

INTERIOR DOUGLAS-FIR. This is the second warmest forest zone of the dry southern interior of British Columbia, occurring in the rain shadow of the Coast, Selkirk and Purcell Mountains. Douglas-fir is the dominant tree. Fires have resulted in even-aged lodgepole pine stands at higher elevations in many areas. Ponderosa pine is the common seral tree at the lower elevations. Pinegrass and feathermoss dominates the understory. Soopolallie and kinnikinnick are common shrubs. Along its drier limits, the zone often becomes savannah-like, supporting bunchgrasses, including rough fescue and Bluebunch wheatgrass.

INTERIOR CEDAR-HEMLOCK. This zone occurs at lower to middle elevations in the interior wet Belt areas of British Columbia. Winters are cool and wet, and summers are generally warm and dry. Western hemlock and Western red cedar are characteristic trees, but spruce (White-Engelmann hybrids) and subalpine fir are common. Douglas-fir and lodgepole pine are generally found on the drier sties. Wet sites generally have a dense undergrowth of devil's club and/or skunk cabbage.

COASTAL WESTERN HEMLOCK. This is the typical rainforest of the low elevations on the coast, and just enters the Ecozone in the northwest corner. Western-hemlock and amabilis fir are the dominant trees in old growth forest.

Vold (1992) has summarized the representation of the biogeoclimatic and ecosections of the Montane Cordillera in British Columbia. Table 2 summarizes this composition at the ecoprovince level, and shows them to be very different.

The Interior Douglas-fir zone dominates the Southern Interior ecoprovince, the Engelmann Spruce-Subalpine Fir zone dominates the Southern Interior Mountains, and the Sub Boreal Spruce zone dominates the Sub-Boreal Interior. In the Central Interior ecoprovince, Sub-Boreal Spruce is slightly more dominant than Sub-Boreal Pine-Spruce, the latter only being represented in this ecoprovince.

Boreal White and Black Spruce zone is only present in the Sub-Boreal Interior, and Bunchgrass and Ponderosa Pine zones only occur in the Southern Interior ecoprovince.

Fire is a natural ecological process, especially in the dry interior forests of British Columbia. In the past, fire suppression was seen as a standard method for dealing with forest fires. Today, foresters view fire as an essential instrument of forest regeneration, contributing to a greater diversity of flora and fauna (Anon 1998). Forest fires are expected to increase with climate change over the next 50-100 years (McBean and Thomas 1992; Perry 1992).

During this century, fire prevention, along with urbanization, domestic livestock grazing, forest harvesting and the building of road networks have changed the landscape substantially. Fire suppression activities have increased the average fire interval dramatically (Table 3). The historical fire frequency in the dry interior varied between 7 and 20 years. In more recent times, most sites have not had fires for 30 to nearly 90 years (Daigle 1996). Excluding fire has altered the forests in a number of ways, including increased tree density, changed forest floor litter from a leaves-herb-needles mix to a primarily needles-twig mix, and changed species composition such as to favour shade tolerant trees and cause the shrub and herb vegetation to be less diverse (Daigle 1996). As a consequence, we can expect fire suppression to have changed diversity considerable over the last century.

Table 4 summarizes data from Vold (1992) on the Ecozone in British Columbia, with respect to protected area, roaded and roadless percentages of the ecoprovince areas. In this analysis, roadless areas are defined as being greater than 1000 ha in size, and greater than 1 km from a road. Over 50% of the Central Interior, Southern Interior Mountains and Southern Interior ecoprovinces are roaded. In the Southern Interior ecoprovince, which is 90% roaded, some areas such as the South Okanagan Basin and South Okanagan Highland ecosections are 100% roaded, as is the East Kootenay Trench ecosection (see Harding and McCullum 1994; Northcote 1998). Indeed, these are the only three ecosections in the whole of British Columbia that are 100% roaded.

While the Interior Douglas Fir zone is the dominant ecosystem in the East Kootenay Trench and South Okanagan Highlands ecosections, the Bunchgrass zone is dominant in the South Okanagan Basin ecosection (Vold 1992). In all three of these ecosections, there are no large areas (greater than I 000 ha) in park or wilderness (Vold 1992). Table 4 shows that as of 1992, only 2% of the Southern Interior and Sub-Boreal Interior ecoprovinces were in park or wilderness.

General ecosystem protection needs in the four ecoprovinces in British Columbia have been outlined by the Endangered Spaces Campaign Initiative of the Canadian Parks and Wilderness Society (CPAWS 1992, 1993, 1994). Currently, biodiversity conservation in the province is being planned to accommodate two complementary strategies, namely a network of protected areas, and the use of integrated resource management outside the protected areas (Scudder 1995).

The need and selection of protected areas within British Columbia over the past few years have included a Protected Areas Strategy (PAS), the Commission on Resources and the Environment (CORE) and now Land and Resource Management Plans (LRMP). These more integrative efforts replaced earlier (pre 1990) separate initiatives setting aside parks, ecological reserves, wilderness areas and wildlife management zones (Table 5).

The figure below summarizes the current status of regional and subregional land use planning in British Columbia, with the superimposed outline of the four ecoprovinces of the Montane Cordillera ecozone on this planning map. It is clear that the current regional and subregional planning process does not, and cannot, consider the ecozone as a whole. The result is that landscape ecosystem conservation planning in the ecozone is being done in a fragmented manner.

At the subregional level, some local landscape level planning is evident in the designation of land use. For example, in the Cariboo-Chilcotin Land Use Plan, where there are 17 protected areas joined by special management zones, in which integrated resource use, including conservation, is mandated.

However, taken as a whole, the protected areas in the province and Montane Cordillera ecozone are scattered and fragmented and do not form a coordinated landscape plan with secure core areas and corridors as now recommended by conservation biologists (Noss 1992).

As noted by Soulé and Sanjayan (1998) even though 12% of the total area of the province may soon be protected, many ecosystems - such as interior Douglas fir and the bunchgrass ecosystems - will have far less than 12% representation, whereas other economically less valuable and less diverse vegetation types will have more than 12%.

The interior Dry Belt in the Montane Cordillera ecozone, which comprises interior Douglas fir (IDFxh1, IDFxh2), Ponderosa Pine (PPxh1, PPxh2) and Bunchgrass (BGxh1, BGxh2) ecozones, and contains most of the Red listed (endangered or threatened) and Blue listed (vulnerable) vascular plants and vertebrates (Harper et al. 1994; Straley and Douglas 1994), and most of the potentially rare and endangered terrestrial and freshwater invertebrates (Scudder 1994, 1996), has very few protected areas. What areas are protected in this Dry Belt are too few, too scattered and too isolated for effective biodiversity conservation (Scudder 1993).

This fact is well illustrated in the Cariboo-Chilcotin subregion, where very few protected areas are mapped on the Dry Belt. Detailed analysis also shows that a number of those within the Dry Belt are actually water bodies with recreational attributes.

As noted by Scudder (1995) and Soulé and Sanjayan (1998), while the first goal of the provincial PAS is to protect viable, representative examples of natural diversity, the measure of diversity in the PAS is limited to an assessment of an area’s richness, and this is richness as it applies to natural, cultural heritage, and recreational values. In other words, diversity in this context is not synonymous with biological diversity and richness is not just species richness (Scudder 1995). Political pressures have led to the substitution of recreational and economic criteria for an earlier, biologically based, process of reserve selection (Soulé and Sanjayan 1998).

The selection of this protected areas network in the province and the Montane Cordillera ecozone has not so far been based on any systematic process involving decisions based on the principles of complimentarity and irreplaceability (Pressey et al. 1994; Margules et al. 1994). As a result, here in the ecozone, as elsewhere in the world, the larger protected areas are poorly allocated for protecting the species-rich, endemic or rare taxa (Pimm and Lawton 1998).

Although some of the protected areas have been selected using vertebrates as focal or indicator taxa or surrogates, it is clear that this strategy is unsound, and holds little promise as a biodiversity conservation planning tool and strategy (van Jaarsveld et al. 1998; Pimm and Lawton 1998). In spite of the fact that there is generally little overlap between richness hotspots and rarity hotspots, and little overlap between taxa using measures of richness and rarity (Pendergast et al. 1993; van Jaarsveld 1998), complimentarity algorithms, used wisely can be effective planning tools, and can bring about cost effective protected areas and reserve selection (Pimm and Lawton 1998; Ando et al. 1998).

Biodiversity conservation in the Montane Cordillera ecozone is not in good shape, and should be assessed further and closely monitored. With less than 2% of the Dry Belt in the southern areas of the ecozone protected, and with little hope of increasing this percentage, as judged by recent LRMP decisions in the relevant subregions, many of the officially designated rare species in the ecozone, plus many now on the B.C. provincial Red list seem doomed to extirpation or extinction.

The 12% protected areas target has no scientific basis (Scudder 1995). This target is politically expedient, and it is certain that targets based on ecological knowledge would be much higher, but politically unacceptable (Soulé and Sanjayan 1998). In the few detailed studies available, the typical estimate of the land area needed to represent and protect most elements of biodiversity, including wide-ranging animal species, is about 50% (Soulé 1987; Gilpin and Soulé 1986; Soulé and Sanjayan 1998).

Studies of the requirements for grizzly bear conservation in the ecozone suggest that about one-third of the area of British Columbia is needed for the maintenance of a minimum viable population (Noss et al. 1996). Furthermore, the range and movements of this species in the Pacific Northwest involves several areas of political jurisdiction. Although specific conservation plans are in place for this species and other large carnivores, future monitoring of these major predators in the ecozone is essential.

However, large vertebrate predators are not surrogates for protecting the rest of the endangered biodiversity in the ecozone. The range map for the grizzly bear is totally outside the Dry Belt area in which most other endangered species occur.

There is an urgent need for macrogeographic integrated landscape planning in the Dry Belt in the ecozone. Such planning is already underway in the Northern Continental Divide ecoregion in Alberta (D. Olson, pers. comm.), and a similar study is in the planning stage for the South Okanagan Basin ecodistrict (K. Freemark, pers. comm.).

Olson & Olson, a planning and design consulting firm in Calgary, is leading a multidisciplinary regional study in the Border Ranges and adjacent areas in the southern east slopes of the Rocky Mountains. The aim is to develop planning tools that can be used to evaluate ecological and socio-economic impacts on landscape biodiversity. Using sophisticated GIS applications, a suite of simulation, analysis and design tools are being developed. The study is examining the history of the region, as well as the process that underlie landscape function. Models are being developed that project potential alternative scenarios, and that identify the associated impacts of those alternatives over time. Based upon the principles of landscape ecology and sustainable ecosystem development, these models may be the only effective way to conserve biodiversity (White et al. 1997), and at the same time maintain sustainable ecosystem development in the Montane Cordillera ecozone. In the South Okanagan Basin ecodistrict, habitat renewal (Sinclair et al. 1995) is going to become a major task in the years to come.

SUMMARY

GENERAL CONCLUSIONS

The chapters that follow document that species diversity is changing at various rates in different taxa and guilds and in the different Montane Cordilleran ecoregions. Many forest dependent species with reticulate distributions on mountain ranges are vulnerable to fragmentation of ranges brought about by the opening of transportation corridors for resource extraction or recreational development. Extensive clear-cutting, selective reforestation and fire suppression are interacting to change the species composition of forested ecoregions. Many grassland species that occur throughout the interior basins and ranges of western North America reach the northern limit of their distributions in the southern plateaus and valleys of the Southern Interior. Conversion of habitat in this ecoprovince for agricultural and residential development is transforming the landscape on a massive scale. Numerous native species associated with sage and bunch grass habitats survive as isolated populations that are becoming unsustainable. Many aquatic plants and animals associated with lentic habitats in the Ecozone, especially saline lakes and ponds, are also found only in the valleys of the Southern Interior. Species inhabiting streams and springs have restricted and often highly disjunct distributions at higher elevations. In both cases, habitat degradation has profoundly affected regional species distributions and now threatens populations of species found nowhere else in Canada.

RECOMMENDATIONS

In order to support societal priorities to use biological resources sustainably and to protect the habitats of threatened populations, species and communities in the Montane Cordillera Ecozone, we recommend that resources be focused on research and monitoring in areas where the impacts of human activities are intensifying, especially in the ecoregions of the Southern Interior Ecoprovince. We further recommend that the capacity to interpret and use species diversity information throughout the Ecozone be strengthened by:

1. Standardizing the recording and storage of taxonomic, spatial and temporal data associated with specimens and species.
2. Increasing the comprehensiveness of baseline information on species, communities and ecosystems.
3. Enhancing access to this information in electronic formats.
4. Integrating and extending monitoring programs on species, communities and ecosystems.
5. Improving analytical tools for assessing spatial and temporal changes in species diversity, community and ecosystem structure and habitat availability.

We thank Michelle MacKenzie for her essential role in assembling and organizing this report. Research for this study was provided by funds from the EMAN program of Environment Canada, and research grants to G.G.E. Scudder from the Natural Sciences and Engineering Research Council of Canada. We thank D.A. Demarchi (B.C. Ministry of Environment, Lands and Parks), D. Olson (Olson & Olson, Calgary), K. Freemark (Canadian Wildlife Service, Environment Canada) for their assistance. L. Lucas prepared some of the figures and tables, and assisted in manuscript preparation.

• REFERENCES
• TABLE 1
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