Appendix D: Ecosystem services potential: Boreal forest case study methodology

The boreal forest case study is a proof-of-concept research and development activity conducted by Environment Canada and Natural Resources Canada as part of the MEGS initiative. This issue of Human Activity and the Environment includes results for a single ecosystem service—water purification—that was included in a larger study on the potential to provide 10 services across Canadian boreal forest. This study is undergoing further review and validation.

Ecosystem services included in the case study were selected based on their relevance to broad-scale assessment, federal policy, and the study scope, the importance of the service, and the likelihood of success in spatially mapping the indicator.

The ecosystem potential analyses included the identification of the key service-specific biophysical processes and drivers, their relationships with the targeted ecosystem services, and the development of quantitative models to provide coarse estimation of ecosystem potential for each selected service. The models incorporate biophysical data, such as climatic variables, topography, landscape structure and configuration as well as land cover data. This approach complements the human landscape modification analysis in section 3.2, which covers a broader geographic area, but only uses land cover and land use variables to coarsely evaluate overall ecosystem integrity.

For each individual service, the case study sought out the best available model to assess potential from published and peer reviewed literature and expert opinion. The best available model was selected and modified based primarily on the performance of biophysical models, their ecological relevance in the boreal, the availability of reliable spatially explicit data to reflect the key biophysical process represented in the model and the sensitivity to changes in management decisions.

The spatial extent of this case study was watersheds that fall almost entirely within the Canadian boreal forest region. The watershed was used as the unit of analysis. This selection was based on the fact that watershed delineations are ecologically meaningful and relevant for decision-making and that this spatial resolution was suitable for ensuring both data availability and feasibility of data processing.

For the integrated assessment of the overall spatial variability of service delivery, the project used flower diagrams which allow for the representation of the magnitude of delivery of multiple ecosystem services, without masking the individual contribution of each to the overall service potential.

Water purification: methods, data sources and calculations

The objective of this part of the study was to estimate water purification potential across Canadian boreal forest watersheds based on landscape conditions and related environmental quality indicators.

The methodology selected is consistent with and builds on an analysis conducted across the continental United States by the US Forest Service. 1 , 2  The extent of analysis corresponds to all watersheds that fall completely within Canada’s boreal zone. 3 

The selected predictor variables used to assess the water purification potential index, additional information on the datasets used and associated data sources, as well as the scoring scheme associated with ranges of values within the distribution of observed values by attribute, are provided in Tables 1 and 2 (Appendix D).

Various partitioning techniques were used to identify the score associated with each potential value of an attribute. When there was sufficient knowledge to support the identification of an ecological threshold for a given attribute as it related to water purification, then such information was used to identify relative weighting scores for the observed range of variability. However, for many ecological phenomena, no clear threshold of response to a selected predictive variable has been observed or reported. The other technique used was to break the distribution in observed values into its respective quartiles.

The Water Purification Potential Index (WaPPI) was calculated for 2000 and 2010 using the above predictor variables as follows:

  1. WaPPI = F + A + R + W + B + LD + HF + S + NS

where F equals percent forested land by watershed; A equals percent agricultural land by watershed; R equals weighted percent riparian forest cover; W equals percent wetlands; B equals weighted percent burn area; LD equals linear density; HF equals human footprint; S equals slope; and NS equals nitrogen and sulphur exceedance level.

For comparison purposes, WaPPI was also assessed using a different national dataset for total disturbance (TD) and edge density (ED).

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