Factors Affecting Ecological Resilience of Reclaimed Oil Sands Uplands

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  • This literature review provides an understanding of ecological resilience as a concept to promote successful land reclamation in Alberta’s mineable oil sands region by exploring four key issues: Defining ecological resilience for boreal forest ecosystems, and assessing whether this definition can be applied to reclaimed oil sands landscapes or requires modification. Resilience is an emergent property of ecosystems. It is an outcome of their inherent capacity for self-organization – the interaction between structure and process that leads to system development. Resilience constitutes the relative susceptibility of a given community to switches into alternative states as a result of the interaction between autogenic (competition, for example), allogenic (fire, wind, harvesting, and climate, as examples) and biogenic (insect epidemics, diseases, as examples) processes. In principle, the concept of resilience could have considerable utility in designing reclamation systems for the oil sands. One application of the concept, the length of time that a system takes to return to equilibrium following perturbation (engineering resilience), is to use rates and patterns of development from the natural forested ecosystems in the region as a benchmark. Hence, the resilience of reclaimed systems would be evaluated with respect to the extent to which these patterns and rates are congruent. Several metrics in the current version of the Guidelines for Reclamation to Forest Vegetation in the Athabasca Oil Sands Region (indicator species and similarity indices, for example) suggest the utility of this approach has been recognized, though not necessarily within the context of resilience. Ecological resilience, the amount of perturbation a system can withstand before it moves into a different state, is pertinent because it constitutes the conceptual basis for designing practices that confer resilience in reclaimed ecosystems. Examples of these practices include minimizing chronic stress (acid deposition, for example), ensuring the rooting zone is conducive to plant establishment and productivity, and a functionally diverse community (both and above and belowground). Resilience in natural and reclaimed ecosystems are mirror images. Applying the concept in natural systems is to pose the question, “how much can self-organizing capabilities be perturbed and still achieve desired outcomes”? In the case of reclamation the question becomes, “how much of the self-organization capabilities of a system must be created to achieve desired outcomes?” Describing a range of ecological and anthropogenic disturbances a reclaimed oil sands upland site might experience In terms of the ecological disturbances a reclaimed oil sands upland site might experience, these are fire, insects and pathogens, drought, wind, site dominance (invasion) by non-local species (native and non-native), and climate variability. Anthropogenic disturbances include erosion, issues associated with soil structure and related physical properties, salinity and sodicity, contaminants (bitumen, naphthenic acids), excessively high and low soil pH, and climate change. Describing physical, chemical and biological characteristics of reclaimed upland sites that would confer resilience to the range of ecological and anthropogenic disturbances identified above Three approaches are described for addressing the physical, chemical and biological characteristics (structure, composition, function) of reclaimed upland sites that would confer resilience to the range of ecological and anthropogenic disturbances identified above. From the general to the specific, these approaches focus on (a) general ecosystem attributes, (b) on functions that need to be maintained, and (c) attributes that confer resilience against specific perturbations or stressors. Describing reclamation and management practices necessary to generate ecological resilience in oil sands upland landscapes Managing for resilience is to implement reclamation practices and procedures that maximize the probability a given desired state will emerge or persist over the time period of interest. The underpinning of resilient ecosystems is a rooting zone conducive to plant establishment and productivity, with a functionally diverse community (both above and belowground) to maximize the potential that development will be maintained along desired trajectories. To create resilient ecosystems, management must focus on both mitigative and adaptive strategies. Mitigative actions confer resilience by eliminating or reducing exposure to chronic stresses (nitrogen and sulfur deposition or salt intrusion, for example). The adaptive approach focuses on traits that allow plant species to tolerate chronic stress or that predispose them to changes in the disturbance regime (fire or climate change, for example). To measure resilience one needs to define the time scale over which a system is resilient, with the choice of scale dependent of the issue under investigation. In the case of reclamation, relevant scales could vary from several decades (the time period over which a reclamation certificate might be awarded) to a century, or more. In principle, resilience could be predicted from models that incorporate the critical processes driving ecosystem productivity and community development but in practice, this is likely not practical due to data limitations. Nevertheless, models can play a useful role in identifying indicators that may signal ecosystem resilience and vulnerability. The review identifies the top three characteristics that confer ecological resilience in oil sand upland landscapes. These are 1. Species diversity, with a particular emphasis on functional diversity 2. A quality rooting zone 3. Minimize nitrogen and sulfur deposition. Designing and assessing resilience in reclaimed oil sands ecosystems will likely require a combination of empirical measures informed by model outputs. Models can be used to project the long-term consequences of a given reclamation prescription while specifying which particular ecosystem attributes are relevant to a monitoring program and the time frame when the requirements for a reclamation certificate could be met. In that respect, model outputs, ecological measures, and checklists which identify management activities, decisions and interventions should be developed collectively, and comprise a decision support system that can address the question ‘Does this reclaimed upland site possess or is capable of developing, characteristics of a resilient ecosystem?’

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    Attribution 3.0 International