Canadian Boreal Forests: The Great Unknown
Northern Screech Owl Photo: Jim Butler
Bunchberries Photo: Jim Butler
Trembling Aspen Photo: Jim Butler
By Dr. Jim Butler
Forty-eight percent of Canada's land mass is forested, and boreal forest makes up the vast majority of this.
This type of forest, however, remains one of the least understood ecosystems in the world. The current rate of deforestation and ecological modification seriously threatens the forest's biological diversity. Much wildlife will be lost forever, and the boreal forest's complex interrelationships will never truly be understood.
The problem of how we know of boreal forest vertebrates strikes us when we discover Eastern screech owl populations in the Swan Hills of Alberta. Our knowledge of boreal forest invertebrates remains so poor that we can only shrug our shoulders when a spider, Dolomedes striatus, that has not previously been known west of Ontario, is discovered in Wagner Bog Natural Area, a mixed wood boreal forest west of Edmonton. Estimates suggest that two-thirds of the living organisms in the world have not yet been given scientific names. How many new species are yet to be identified in boreal environments? How many extinctions are occurring now from forestry operations?
The impact of forest harvesting on boreal forest wildlife habitats is poorly understood.
While some important boreal wildlife studies have been done, they fall far short of contributing the knowledge base we so desperately need in view of the acceleration of forest resource allocations. Traditionally, most forest-related research has focused on industrial-productivity objectives. With Canadian University scientists largely dependent upon industry funding for their forest-directed research, this is not likely to change. Ontario is spending about $30 million dollars on environmental impact assessments for timber management studies at the present time, but in Alberta, no environmental impact assessment is generally done for forestry operations. Impacts on wildlife are rarely considered beyond concerns for sport animals, such as moose and deer.
What We Do Know...
Boreal forests naturally have a mixed wood composition. Aspen and spruce (the two main species) have different life cycles, not easily regenerated in the mixed mosaic that contributes to the area's remarkable ecological diversity. Mature and old growth forest stands provide many mammals and birds with thermal shelter during cold winters. Aspen hollows out with internal rot at 50 to 60 years, and fires leave many standing dead trees, which are a critical resource for birds that absolutely require cavities in trees for nesting (Hawk Owl), and birds that feed on invertebrates within rotting wood (e.g., many woodpeckers). Old aspen and poplar adjacent to mature conifers form an important interface for many wildlife species who nest in the cavities of the aspen and popular, and return to the old spruce for concealment and thermal cover.
A close linkage exists between woodland caribou and old growth coniferous forests in northern Alberta. Other species which are dependent on old-growth boreal forest include Great Gray Owls, Woodland Caribou, wolves, marten, fisher, Northern Flying squirrels, woodpeckers, cavity-nesting birds and mammals, Golden-crowned kinglets, Brown creepers, or the Blackburnian, Bay Breasted, Cape May and Black-throated Green Warbler, and the Philadephia vireo.
Forest Mismanagement As it Exists Today
Old ideas about old-growth trees die hard in those trained in the narrow objectives of forest harvesting. Leaving a significant portion of older trees (200 years plus by boreal standards) doesn't make sense if you think of forests as tomato patches with older plants going to waste if not collected. Furthermore, the denser wood of older spruce trees is most desired for the market place. The schools which trained this industrial generation measured wildlife benefits only in reference to the sport achieved from better moose and deer browse. Wildlife of little homocentric importance rarely mattered, nor did ecological objectives for sustaining the integrity or composition of the wildlife community.
While some important boreal wildlife studies have been done, they fall far short of contributing the knowledge base we so desperately need in view of the acceleration of forest resource allocations.
The impact of forest harvesting on boreal forest wildlife habitats is poorly understood. Some species, such as certain ungulates (e.g., moose and deer), mice populations (e.g., microtus), and "generalist" bird species which favor clearings (e.g., cowbirds, crows, and starlings) may "benefit" by the creation of a patchwork of early successional landscape on forested lands. The majority of species that occupy old growth, mature, or uneven aged forest stands, however, are almost certainly negatively effected.
Forest fragmentation results from logging of the most accessible and/or more productive sites, leaving remaining forest stands of varying size and degrees of isolation. Generally fragmentation from forest clearing reduces species populations and compositions. It favours the common edge species with small home-range requirements, and selects against species requiring forest core environments and large forage ranges.
Forest wildlife ecologists today are concerned about 'edge effect', the ecological alteration of forest wildlife communities in the interior of the forest surrounding a new clearing. Forest wildlife impacts are acute for a distance of 200 meters beyond the edge of a forest clearing due to an interior invasion of "generalist" open country or edge species. This invasion amplifies competition and predation, displacing many forest interior species. This area of alteration extends for a moderate degree to a full range of 600 meters. Forest interior core species (eg., Brown creepers and Three-toed woodpeckers) are the first to be displaced. Substitution of species from edge effects will significantly alter the forest wildlife community if forest fragmentation is excessive.
Leaving a significant portion of older trees (200 years plus by boreal standards) does't make sense if you think of forests as tomato patches with older plants going to waste if not collected.
New pulp mills in the boreal forest make aspen their central focus. Aspen stands achieve about seventy percent of their maximum volume by the age of twenty years. The internal rot which begins at age 50 or 60 is not desirable to the pulp business, since it reduces the strength and brightness of pulp. The "solution" is to cut aspen in short (e.g. 25 year) rotations for optimum yield, long before they reach their prime for wildlife habitat. Such extensive changes will drastically reduce the numbers of many boreal wildlife species.
Many of the migrant song bird species are already under stress from forest habitat destruction in their wintering grounds in Central America. Cavity-nesting species are particularly threatened by present forestry practices. The creation of successional forest through clear-cut logging does not provide the same habitats as those which are naturally created by fire. Standing dead trees are becoming increasingly uncommon, making it difficult for many species to find suitable nesting locations. Removing dying or dead wood will improverish the forest wildlife by 2/5 to 1/2. Cavities are often so scarce in forests that in one instance a single cavity was found to contain the eggs of a hooded merganser, a goldeneye and a barred owl.
Bay Breasted Warbler Photo: Jim Butler
Pink Ladyslipper Photo: Jim Butler
Campfire-Clearwater River Photo: Jerry Paschen
A close linkage exists between woodland caribou and old growth coniferous forests in northern Alberta. Other species which are dependent on old-growth boreal forest include Great Gray Owls, Woodland Caribou, wolves, marten, fisher, Northern Flying squirrels, woodpeckers, cavity-nesting birds and mammals, Golden-crowned kinglets, Brown creepers, or the Blackburnian, Bay Breasted, Cape May and Black-throated Green warbler, and the Philadephia vireo.
Who Wins, Who Loses, Who Lives, Who Dies
An analysis of the exchange between wildlife "winners and losers" was conducted by several of Alberta's leading wildlife professors and biologists during the 1989 Environmental Impact Assessment process which examined wildlife impacts of the Alberta-Pacific Pulp Mill near Athabasca, Alberta. 309 species of wildlife vertebrate animals were believed to occupy the land and water area allocated exclusively to the world's largest single line bleached kraft mill. Of these, 59 species were seen to be positively affected by the pulp mill and associated logging operations, 27 species were classified as neutral and 229 species (74%) were classified as negatively effected.
Of that total, 13% (40 species) were identified as wildlife species "of special concern" because they were rare, threatened or endangered. This 13% suggests the proportion of wildlife species that would be in trouble in the boreal forest in general; in old growth areas which contain a great many specialized species this proportion can be expected to be still higher. Exact figures are scarce or suppressed but certainly less than ten percent of old growth still remains.
A sense of the individual numbers of wildlife affected is important to realize the true impact of industrial operations upon wildlife. While individual losses are presented as a prime statistic in the impact of human tragedies from earthquakes to plane disasters, we rarely have a sense of its scale during forestry developments.
A thirty-eight hectare area of mixed wood boreal forest was studied to calculate the inventory and populations for all wildlife vertebrates. When the numbers per hectare were extrapolated to the 61,000 sq km. Forest Management Area (FMA) for the AlPac pulp mill near Athabasca, Alberta, the numbers are staggering. The nearly 300 species of land vertebrates resident in this FMA would number over 1.5 billion individuals. Following the 1989 estimate that 74% of these species would be negatively effected, and accepting AlPac's calculations that only half of the land area would be impacted by forestry (disregarding other forms of impact, including fragmentation and edge-effect) the result is that more than 600 million wildlife individuals would be losers, a "trade-off" for the price of "progress." As a reference point, this number represents twice the human population for all of North America. Any event which removed the habitat or homes, twice over, of the entire North American continent would be an event worthy of causing pause.
Forest management is usually based on the interpretation of aerial photographs and concerns preferred commercial tree species, crown closure and height of stand. The decision process lacks important wildlife variables such as understory structure, the presence of critical habitat features such as snags and fallen logs, an inventory of the wildlife community, more extended rotation cycles, and objectives to protect areas of old growth, and sustain the integrity of the wildlife community under principles of ecosystem conservation. Just as society has declared that war is too significant to be left to the decisions of Generals; so the boreal forests are too significant to be left to the decisions of the Forest Industry.
Dr. Jim Butler is a professor of Parks, Wildlife and conservation Biology with the University of Alberta's Department of Forest Science.
