Canadian Boreal Zone Research Articles

Long-term environmental changes in the Canadian boreal zone: Synthesizing temporal trends from lake sediment archives to inform future sustainability

Covering 55% of Canada’s total surface area and stretching from coast to coast to coast, the Canadian boreal zone is crucial to the nation’s economic and ecological integrity. Although often viewed as relatively underdeveloped, it is vulnerable to numerous stressors such as mining, forestry, and anthropogenic climate change. Natural archives preserved in lake sediments can provide key insights by quantifying pre-disturbance conditions (pre-1850 CE) and the nature, magnitude, direction, and speed of environmental change induced by anthropogenic stressors over the past ∼150 years. Here, we paired a review of paleolimnological literature of the Canadian boreal zone with analyses of published sediment core data to highlight the effects of climate change, catchment disturbances, and atmospheric deposition on boreal lakes. Specifically, we conducted quantitative syntheses of two lake health indicators: elemental lead (Pb) and chlorophyll a. Segmented regressions and Mann–Kendall trend analysis revealed a generally increasing trend in elemental Pb across the boreal zone until ∼1970 CE, followed by a generally decreasing trend to the present. Snapshot comparisons of sedimentary chlorophyll a from recent and pre-industrial sediments (i.e., top-bottom sediment core design) revealed that a majority of sites have increased over time, suggesting a general enhancement in lake primary production across the boreal zone. Collectively, this body of work demonstrates that long-term sediment records offer a critical perspective on ecosystem change not accessible through routine monitoring programs. We advocate using modern datasets in tandem with paleolimnology to establish baseline conditions, measure ecosystem changes, and set meaningful management targets.

Influence of competition on root architecture and root anchorage of young hybrid poplar plantations on waste rock slopes

ABSTRACT Root systems are crucial to tree and soil stability in terms of mechanical support, but are rarely considered in revegetation studies. This study aimed at determining the effect of planting density and herbaceous hydroseeding on the root architecture and mechanical resistance to uprooting of planted hybrid poplars on waste rock piles. The study took place at an open pit gold mine in the Canadian boreal zone where a hybrid poplar plantation was established in 2013 on soil-covered waste rock slopes (33%). Four treatments were randomly distributed in three replicated blocks: 4 × 4 m, 2 × 2 m, 1 × 1 m between trees and 2 × 2 m + h, corresponding to trees spaced at 2 × 2 m with hydroseeding. Lateral uprooting tests of four-year-old hybrid poplars were conducted in the direction of the slope. Maximum resistance to the uprooting force was observed in the 2 × 2 m treatment. Root systems were more symmetrical, deep, branched, and had higher root diameters in the 2 × 2 m and 4 × 4 m treatments. In contrast, the treatments with greater intra- or interspecific competition showed shallower, asymmetrical root systems with smaller roots. Therefore, competition significantly reduced tree anchorage.

Sequential droughts: A silent trigger of boreal forest mortality.

Despite great concern for drought-driven forest mortality, the effects of frequent low-intensity droughts have been largely overlooked in the boreal forest because of their negligible impacts over the short term. In this study, we used data from 6876 permanent plots distributed across most of the Canadian boreal zone to assess the effects of repeated low-intensity droughts on forest mortality. Specifically, we compared the relative impact of sequential years under low-intensity dry conditions with the effects of variables related to the intensity of dry conditions, stand characteristics, and local climate. Then, we searched for thresholds in forest mortality as a function of the number of years between two forest surveys affected by dry conditions of any intensity. Our results showed that, in general, frequent low-intensity dry conditions had stronger effects on forest mortality than the intensity of the driest conditions in the plot. Frequent low-intensity dry conditions acted as an inciting factor of forest mortality exacerbated by stand characteristics and environmental conditions. Overall, the mortality of forests dominated by shade-tolerant conifers was significantly and positively related to frequent low-intensity dry conditions, supporting, in some cases, the existence of thresholds delimiting contrasting responses to drought. In mixtures with broadleaf species, however, sequential dry conditions had a negligible impact. The effects of frequent dry conditions on shade-intolerant forests mainly depended on local climate, inciting or mitigating the mortality of forests located in wet places and dominated by broadleaf species or jack pine, respectively. Our results highlight the importance of assessing not only climate-driven extreme events but also repeated disturbances of low intensity. In the long term, the smooth response of forests to dry conditions might abruptly change leading to disproportional mortality triggered by accumulated stress conditions. Forest and wildlife managers should consider the cumulative effects of climate change on mortality to avoid shortfalls in timber and habitat.

Stand-Level Fuel Reduction Treatments and Fire Behaviour in Canadian Boreal Conifer Forests

Stand-level fuel reduction treatments in the Canadian boreal zone are used predominantly in community protection settings to alter the natural structure of dominant boreal conifer stands such as black spruce (Picea mariana (Mill.) BSP), jack pine (Pinus banksiana Lamb.) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia). The aim of these fuel treatments is to inhibit the development of fast-spreading, high-intensity crown fires that naturally occur in boreal forest ecosystems. We document fuel treatment design standards used in boreal forests in Canada and review data requirements and methodological approaches for investigating fuel treatment effects on fire behaviour. Through a series of illustrative examples and summaries of empirical observations, we explore the implications of data and modelling assumptions used to estimate fire behaviour in fuel-treated areas and identify insights about fuel treatment effectiveness in boreal conifer stands. Fuel treatments in black spruce, jack pine and lodgepole pine stands were generally effective at reducing modelled and observed fire behaviour and inhibiting crown fire development and spread under low to moderate fire weather conditions. Evidence suggests that fuel treatments in these fuel types will be ineffective when rates of spread and wind speeds are very high or extreme. High surface fuel loads combined with the relatively short stature of boreal conifer trees can further undermine fuel treatment efforts. Priority areas for future study include examining alternatives for managing surface fuel loads in treated stands, exploring the viability of alternative horizontal fuel reduction protocols such as clumped fuel configurations, and integrating suppression and containment strategies within the fuel treatment planning and design process.

Atmospheric change as a driver of change in the Canadian boreal zone1

Global anthropogenic emissions of greenhouse gases and hazardous air pollutants have produced broad yet regionally disparate changes in climatic conditions and pollutant deposition in the Canadian boreal zone (the boreal). Adapting boreal resource management to atmospheric change requires a holistic understanding and awareness of the ongoing and future responses of terrestrial and freshwater ecosystems in this vast, heterogeneous landscape. To integrate existing knowledge of and generate new insights from the broad-scale impacts of atmospheric change, we first describe historical and present trends (∼1980–2015) in temperature, precipitation, deposition of hazardous air pollutants, and atmospheric-mediated natural disturbance regimes in this region. We then examine their associations with ecosystem condition and productivity, biological diversity, soil and water, and the carbon budget. These associations vary considerably among ecozones and likely undergo further changes under the emerging risks of atmospheric change. We highlight the urgent need to establish long-term, boreal-wide monitoring for many key components of freshwater ecosystems to better understand and project the influences of atmospheric change on boreal water resources. We also formulate three divergent future scenarios of boreal ecosystems in 2050. Our scenario analysis reveals multiple undesirable changes in boreal ecosystem structure and functioning with more variable atmospheric conditions and frequent land disturbances, while continuing business-as-usual management of natural resources. It is possible, though challenging, to reduce unwanted consequences to ecosystems through management regimes focussed on socio-ecological sustainability and developing resilient infrastructure and adaptive resource-management strategies. We emphasize the need for proactive actions and improved foresight for all sectors of society to collaborate, innovate, and invest in anticipation of impending global atmospheric change, without which the boreal zone will face a dim future.

Managing risks to Canada’s boreal zone: transdisciplinary thinking in pursuit of sustainability1

The policy landscape is changing as Canada considers its energy future. The Canadian boreal zone has a large amount of natural resources, giving Canada options in terms of its energy future. However, the sustainability of the boreal zone has been deemed at risk because of the cumulative effects of intensifying natural resource activities (forestry, mining, oil and gas, and renewable energy) on ecosystems in the face of the uncertainty associated with climate change. As Canada considers the future of the boreal zone, there will be additional challenges to ensure that we do not further disadvantage marginalized human populations living in the boreal zone who are at high risk of the consequences of climate change. In response to these challenges, the Boreal 2050 project was initiated to understand the risk of failing to achieve the future sustainability of the boreal zone using the ISO 31000 risk management framework. First, we identified the major drivers of the risks to the sustainability of the boreal zone, which include atmospheric change, the demand for provisioning and nonprovisioning ecosystem services, demographics and societal values, industrial innovation and infrastructure, and governance. Second, we analyzed the risk of failing to achieve a sustainable boreal zone using scenario analysis, where we framed four plausible future scenarios around two axes of change: the global economy’s energy and society’s capacity to adapt. Third, we evaluated the risk and determined that present governance systems are driving Canada towards failing to achieve a sustainable boreal zone. To ensure the future sustainability of the boreal, we need to shift from an oil/gas/coal-producing country to a renewable energy leader and shift from using a top-down strategy where Canadians have a low capacity to adapt towards a mixture of top-down and bottom-up participatory strategies where Canadians—particularly Indigenous peoples living in the boreal zone—have a higher capacity to adapt. To facilitate this shift in governance, substantive changes will be required in institutional arrangements designed to protect boreal ecosystems.

Reimagining energy in the Canadian boreal zone: policy needs to facilitate a successful transition to a low-carbon energy future1

Canada will be unable to meet its greenhouse gas pledges—of reducing greenhouse gas emissions by 30% over 2005 levels by 2030—without transitioning away from the current high-carbon economy. This transition will bring new challenges, especially to the Canadian boreal zone. The boreal zone continues to experience intensive natural resource activities including the extraction of forest, mining, oil and gas, and renewable energy products, which in combination with climate change, is placing the future sustainability of the boreal zone at risk. We explored policy options to reduce the risk to the future sustainability of the boreal zone in light of the inevitable energy transition to either a higher or a lower dependence on carbon and the uncertainty of society’s capacity to adapt to change. Current policies are putting us on a path towards failure to achieve sustainability of the boreal zone. While current policies may be moving us towards a low-carbon future, they lack a shared vision of what the energy transition will be and engagement by those members of society most impacted; they are top-down, prescriptive, and fragmented, and they lack capacity, accountability, and enforcement. Together these limitations create barriers to society’s capacity to adapt to the low-carbon future. Sustainability of the boreal zone will not only require a transition to a low-carbon economy but will require policies that overcome these barriers and create a higher capacity for society to adapt.

Demographics and social values as drivers of change in the Canadian boreal zone1

The boreal zone, a vast region with abundant natural resources and related industries, has both provisioning and nonprovisioning ecosystem services that draw some people, while warding off others. It is an area that arguably affects many Canadians in different ways and represents a wide range of tangible and intangible values. Changes in demographic patterns over time shed light on the development of the social-ecological landscape of the boreal zone, and elucidate potential changes in the future. Using past and current demographic data, we explore population size, immigration and emigration, and birth and death rates within and outside the boreal zone. We also explore links between demographics, social values, and important factors of change in the boreal zone, and present three contrasting scenarios predicting the state of this zone in 2050. We pay particular attention to the Indigenous population, generational differences, international immigration, and the urban–rural divide. Fertility rates and immigration influence population demographics within and outside the boreal zone, respectively, alluding to potential divergences in social values and between communities located within and outside the boreal zone. The boreal zone is currently comprised of many smaller towns and communities scattered across the landscape, yet it is equally important to consider the influences of larger cities located outside the boreal zone, particularly in terms of governance, population movements, and political power. Considered together, these factors provide insight on social cohesion and connectedness, demand for goods and services, and changes in boreal-centric activities.

Governance as a driver of change in the Canadian boreal zone1

The Canadian boreal forest is primarily public land, owned and managed by provincial governments on behalf of the public interest. Boreal forest governance consists of a complex patchwork of federal and provincial legislation, policies, tenures, and delegated authorities designed to achieve multiple (and often conflicting) social, ecological, and economic objectives. We examine the implications of boreal governance arrangements for sustainable management of ecosystem services. The paper shows how current multi-level governance arrangements that evolved from Canada’s Constitution Act are not effective at managing the cross-scale and cross-sectoral challenges of ecosystem services and have created a crisis of legitimacy for forest decisions. We show how the rise of nonstate arrangements, marketization, and decentralization are partly a response to governance gaps for ecosystem services as well as a reflection of global trends in forest governance. Past trends related to governance themes (the role and scope of government, the level of integration and coordination, Indigenous empowerment, and geopolitical influences) are used to motivate future governance scenarios.

Industrial innovation and infrastructure as drivers of change in the Canadian boreal zone1

Much of Canada’s industrial sector is driven by natural resources and relies heavily on provisioning services supplied by the boreal zone. However, the sometimes intensive processes used by resource-based industries and their associated infrastructure have significantly altered the region, creating concerns over the future socio-ecological health of the boreal zone. Addressing these concerns will require industries reliant on natural resources from the boreal zone to innovate their processes, management, and infrastructure to improve extraction efficiency while contributing to society’s increasing expectations related to sustainability. Here, we explore past, current, and future trends in industrial innovation and infrastructure in the boreal zone for forestry, mining, pulp and paper, oil and gas, and renewable sources of power generation. We assess the role of innovation on the future socio-ecological state of the boreal zone by considering interactions between innovation in industry and infrastructure and other key drivers of change in the boreal, such as atmospheric changes, changing demands for nonprovisioning and provisioning ecosystem services, governance, and demographics and social values. We present future scenarios highlighting three divergent trajectories of change in boreal ecosystems based on past and current states of innovation in industry and infrastructure. We suggest that minimizing impacts of natural resource extraction activities in the boreal zone will only be possible through innovation directly focused on reducing the human footprint on the landscape. Innovation in the information technology sector related to process, management, and end products within these industries and placing greater emphasis on cross-sectoral collaboration will be key to achieving this goal.

Demand for provisioning ecosystem services as a driver of change in the Canadian boreal zone1

The Canadian boreal zone provides extractive goods and services (provisioning ecosystem services (PrES)) to domestic and global markets and makes a significant contribution to the Canadian economy. The intensity and location of these extractive activities, however, may positively or negatively affect the availability of other benefits that the Canadian and global society receive from the boreal. Where PrES compete, managing these activities along with their impacts to boreal ecosystems becomes a balancing act between the need for resource extraction and the continued availability of the other benefits from ecosystems. Management measures and policies are more likely to succeed if they are designed with foresight, which means accounting for how demand, a key driver of change in the boreal, may change in the future. To help this process, we present three divergent, yet plausible future scenarios based on the analysis of: (i) the capacity of the boreal to provide wood products, fossil fuels, metals and minerals, and hydropower and other renewables; (ii) past trends (1985–2015) and key events in the demand for these PrES; (iii) the interaction of demand for PrES with other drivers of change to the boreal zone; and (iv) the synergies and trade-offs between PrES. We find that historically and currently the capacity of the boreal to provide these PrES exceeds the amount currently supplied. However, the capacity of different PrES and location of extractive activities are spatially dispersed creating a spatial and temporal patchwork of associated risks to local ecosystem integrity and the supply of non-PrES. In addition, these scenarios suggest that the future of boreal PrES is very uncertain and highly dependent on how other drivers of change (namely governance and geopolitics, societal values and climate change) play out in the future. Given the spatial complexity, we find that the cumulative effect of these drivers (e.g., climate change) will determine what paths unfold for different areas of the boreal, and we conclude that careful consideration and planning must be given to ensure that the balance between PrES and non-PrES is maintained.

Demand for nonprovisioning ecosystem services as a driver of change in the Canadian boreal zone1

The Canadian boreal zone provides ecosystem services from local to global scales. Either directly or indirectly, demands for these services have and will continue to serve as drivers of change in the region. Here we present evidence for past, present, and potential future demand for maintaining nonprovisioning ecosystem services (NPrES), defined as indirect and nonmarketable services obtained from ecosystems as a driver of change in the boreal zone. Our evidence of demand stems from federal and provincial policies, actions by Indigenous peoples, and nongovernmental initiatives that aim to maintain the sustainability of natural resource extraction and ecosystem condition of the boreal. Presently, the demand for NPrES influences decisions related to natural resource development (e.g., forestry) that in turn impacts the condition of the boreal zone. Informed by the present conditions and past trends, three future scenarios to the year 2050 are presented that contrast in their trajectory—status quo, increased demand for NPrES, and decreased demand for NPrES. We also summarize the interactions among other drivers of change in the boreal and the synergies and trade-offs among the different types of demand for NPrES. Ultimately, sustainability of the boreal zone and the ecosystem services it provides will result from a complex suite of interacting drivers of change, where the balance of demands for provisioning and NPrES will continue to influence regional conditions.

Past and projected future changes in moisture conditions in the Canadian boreal forest

Spatial data for the Climate Moisture Index and the Palmer Drought Severity Index were generated from gridded temperature and precipitation data for the Canadian boreal zone over the period 1951–2010. Annual values for the indices for 2011–2100 were generated from projections of future climate derived from four general circulation models forced by three greenhouse gas emissions scenarios. Linear regression models between the indices and time were fitted to examine long-term trends. Results indicated that several large regions of the Canadian boreal forest experienced substantial drying during 1951–2010. Future projections indicated a general trend toward drier conditions during the 21stcentury. Overall, the analysis indicated more frequent and/or more severe droughts across managed western and central portions of the boreal forest in coming decades. These projections of indices are relevant to forest management because soil moisture availability is an important determinant of forest distribution, tree health, and regeneration success. Knowledge of the range of potential future changes in drought occurrence and intensity will aid forest managers and decisionmakers in incorporating climate change considerations into forest management planning and practices.

How do natural disturbances and human activities affect soils and tree nutrition and growth in the Canadian boreal forest?

There are concerns about the effect of increasing resource extraction and other human activities on the soils and vegetation of the boreal zone. The review covers published papers between 1974 and 2012 to assess the effects of natural disturbances and human activities on soils and tree nutrition and growth of the Canadian boreal zone. Changes in soil and foliar nutrients following disturbance were also analyzed by meta-analysis. When sufficient replicated studies were not available for a given disturbance or nutrient, response assessments or narrative summaries are presented. The majority of fertilization studies in the boreal zone showed a positive tree growth response to nitrogen (N) and phosphorus (P) fertilization either individually or in combination. Large amounts of N may be lost through volatilization following fire depending on the severity and frequency of the fire. This may contribute to N limitation in the boreal zone. Available soil P and extractable calcium (Ca) and magnesium (Mg) increased in the surface horizons following fire. In contrast, extractable P decreased following harvest. Harvesting had no effect on total or inorganic N except in mixedwoods where total N decreased in the surface organic horizon following harvest. These are potential areas of concern given tree growth responses to N and P fertilization. Potassium (K) in the forest floor did not change following fire or harvesting; thus, K availability for tree nutrition should not be at risk, since its cycle is rapidly restored. Mercury (Hg) cycling may be altered in the boreal zone as a result of flooding and if fire return intervals and intensities increase. Interactions of multiple disturbances may increase the risk of nutrient depletions, but there is currently little information on these interactions in the boreal zone. Evidence to date suggests the soils of the Canadian boreal zone have not been adversely affected except in localized areas. However, there is the risk of nutrient loss if soils are not considered in our forest management strategies, particularly where multiple disturbances may interact. The potential for off-site movement of nutrients and contaminants into the atmospheric and aquatic ecosystems, in addition to on-site environmental issues, is also a concern.

Anticipating the consequences of climate change for Canada’s boreal forest ecosystems

Canadian boreal woodlands and forests cover approximately 3.09 × 106 km2, located within a larger boreal zone characterized by cool summers and long cold winters. Warming since the 1850s, increases in annual mean temperature of at least 2 °C between 2000 and 2050 are highly probable. Annual mean temperatures across the Canadian boreal zone could be 4–5 °C warmer than today’s by 2100. All aspects of boreal forest ecosystem function are likely to be affected. Further, several potential “tipping elements” — where exposure to increasing changes in climate may trigger distinct shifts in ecosystem state — can be identified across the Canadian boreal zone. Approximately 40% of the forested area is underlain by permafrost, some of which is already degrading irreversibly, triggering a process of forest decline and re-establishment lasting several decades, while also releasing significant quantities of greenhouse gases that will amplify the future global warming trend. Warmer temperatures coupled with significant changes in the distribution and timing of annual precipitation are likely to cause serious tree-killing droughts in the west; east of the Great Lakes, however, where precipitation is generally nonlimiting, warming coupled with increasing atmospheric carbon dioxide may stimulate higher forest productivity. Large wildfires, which can cause serious economic losses, are expected to become more frequent, but increases in mean annual area burned will be relatively gradual. The most immediate threats could come from endemic forest insect pests that have the potential for population outbreaks in response to relatively small temperature increases. Quantifying the multiple effects of climate change will be challenging, particularly because there are great uncertainties attached to possible interactions among them, as well as with other land-use pressures. Considerable ingenuity will be needed from forest managers and scientists to address the formidable challenges posed by climate change to boreal ecosystems and develop effective strategies to adapt sustainable forest management practices to the impending changes.

Controls on CH4 and CO2 emissions along two moisture gradients in the Canadian boreal zone

Controls on the emission of CH4 and CO2 along moisture gradients in the northern study area of the Boreal Ecosystem‐Atmosphere Study (BOREAS), west of Thompson, Manitoba, were examined in the summer of 1994. A transect stretching from three forested upland sites to an open graminoid fen contained within a black spruce (OBS) palsa was compared with a similar transect from upland lichen and Sphagnum moss sites to wetland mire and pond sites adjacent to an active beaver pond (BP). Mean seasonal CH4 (dark CO2) fluxes were −0.51 (7.99), −0.14 (10.3), 0.15 (8.68), and 2.83 (8.22) mg/m2/d (g/m2/d) from the OBS feather moss, lichen, sphagnum moss, and fen sites. Mean seasonal CH4 (dark CO2) fluxes were −1.58 (9.16), 2.03 (7.62), 1144, and 153 mg/m2/d (g/m2/d) from the BP lichen, sphagnum moss, mire, and pond sites. Rates of CH4 oxidation typical of uplands were observed at all sites except for the BP mire and pond. CH4 efflux was observed in all sites. Rates varied by 4 orders of magnitude along the transition from the driest uplands to moist uplands to inundated wetlands. A high water table appears to be necessary for a strong CH4 source. Low soil temperatures inhibit high CH4 flux rates despite inundation. The potential for the conversion of upland sites from net sinks to sources of CH4 by minor changes in the water table was observed. Prediction of CH4 fluxes by plant community analysis appears to require knowledge of the thermal and hydrologic regime of particular sites over the course of the summer period. Dark CO2 fluxes, by contrast, appear more uniform across similar plant community types.

Spatial variation in composition and richness of fish communities in a southwestern Australian river system

AbstractThirteen species of fish were recorded from the non‐tidal reaches of the Murray River system, southwestern Australia. Of these, nine were indigenous species. Although this system occurs in a zone of moderate to high rainfall, the species richness of this system is comparable to that of much harsher environments, such as the Canadian boreal zone or the Nevada desert. Species richness tends to increase in a downstream direction, and most changes in species composition are due to addition, rather than replacement of species. Stream order was strongly and significantly positively correlated with species richness (P < 0.001), but was in effect functioning as a composite variable. Stepwise multiple regression analysis showed that stream width, pH range, distance from the main stream, distance from the estuary, barriers and stream gradient together explained more than 80% of the variation in species richness. The variables, barriers, distance from the main stream and distance from the estuary, support island biogeography type explanations for variations in species richness, while the variable, stream width complies with the river continuum concept. A predictive model for species richness of any given reach of a lower west coastal stream in Australia was tried using variables that can be gathered almost entirely from detailed topographic maps and aerial photographs.