Maintaining the Portfolio of Wetland Functions on Landscapes: A Rapid Evaluation Tool for Estimating Wetland Functions and Values in Alberta, Canada

Abstract Wetland loss in Alberta, Canada is ongoing despite a policy of no net loss of wetland area that has been in place since 1993. The Government of Alberta (GOA) recently replaced the no-net-loss policy (1993) with a policy of no net loss of wetland function (2013). The GOA commissioned the development of an Alberta Wetland Relative Value Evaluation Tool (ABWRET) to implement the no net loss of wetland function policy. However, the assessment of the more than one million wetlands in Alberta using the “on-the-ground” ABWRET-Actual is not reasonable or realistic, and so a “from-the-sky” ABWRET-Estimator was developed. Together, these ABWRET tools provide planning and regulatory tools to reduce the risk of wetland loss in Alberta. The ABWRET tools assess the following four wetland functions: hydrologic health (HH), water quality (WQ), ecologic health (EH), and human use (HU) for every wetland in the developed and populated area of Alberta. Subfunctions were identified for each function and include: water storage and stream flow support subfunctions for HH; water cooling, sediment retention, phosphorus retention, and nitrate removal subfunctions for WQ; and organic nutrient export, fish habitat, invertebrate habitat, amphibian habitat, water bird nesting habitat, songbird, raptor and mammal habitat, and plant and pollinator habitat subfunctions for EH. The ABWRET-Estimator divides the province into functional units called relative value assessment units (RVAUs) so that wetlands in similar landscapes could be assessed against each other to provide relative estimates of wetland function within that geographic region. Wetland function was assessed for each RVAU by the ABWRET-Estimator using 73 process-based indicators that were estimated using existing geographical information system and remote sensing data. Indicators were standardized from 0 to 1 and combined to establish subfunction scores using models derived from expert opinion and literature review. The subfunction scores were then combined into an overall function score by taking the highest subfunction score for a given function. The overall relative wetland value score for each wetland was then estimated using a weighted average approach of the function scores. Using this information, wetlands were then assigned an a, b, c , or d score based on their relative wetland value score percentile, where a score of a indicated a high functioning wetland. The a, b, c, or d score was then modified based on estimates of historic wetland loss within each RVAU. Function scores were raised by one letter in RVAUs where a high amount of wetland loss has historically occurred to increase wetland protection. Conversely, the relative wetland value score letters were lowered by one letter (not less than d ) in RVAUs with the lowest loss of wetlands to reduce wetland protection. The GOA has a powerful set of tools to implement its new wetland policy. Planners can use the ABWRET-Estimator tool to reduce risk of loss of wetland functions by supporting informed wetland planning and management decisions at both local and watershed scales. Regulators can use the ABWRET-Estimator tool to avoid the loss of high-functioning wetlands when evaluating proposed development activities. A commitment to continuous improvement of the ABWRET tools together with routine monitoring of potential changes in wetland functions will contribute to the reduction of further loss of wetland functions and their associated services for Albertans.