This contribution describes the recent evolution from sector-based environmental management to cumulative effects management (CEM) in Alberta under a new policy direction titled the Alberta Land-use Framework. This paper focuses on the role of models and hypothesis testing in a CEM and performance assurance framework rather than a critique of CEM itself. Two opposing approaches are currently pursued in Alberta to establish the metrics of CEM. Both are outlined and a case is made for reliance on ecologically defined criteria over the potentially dangerous approach of setting socially desired outcomes first. The challenges Alberta regulators face that must be overcome for an ecosystem approach are described under four categories: (1) model suitability, (2) data availability, (3) science representation, and (4) suitability for a regulatory framework. Two case studies are presented that exemplify the success of following an ecosystem modelling approach to CEM and the pitfalls that can occur if the wrong indicators (i.e., ecological end-points that are insensitive to the disturbance) are selected in the CEM approach.