Halfway through, it states that

> The annual rate of wetland loss from existing data (10,820 hectares per year) was used to quantify associated carbon emissions for the region.

but I'm not exactly sure what they mean by "the region", and I can't find that number anywhere in the linked report. But 11k hectares is only 167 quarter sections, which really isn't very much—a typical small/independent farmer will usually plant crops in multiple quarter sections every year. For comparison, Alberta+Saskatchewan are 131 million hectares in area, and if "The Prairies" also includes BC and MB, then the total area doubles.

Without looking at any of the data, my guess would be that most of the areas being drained are in the cities (and not farmland), since that's usually the only place where it makes economic sense to drain a wetland. And even the cities tend to preserve the wetlands these days since they're a pretty cheap solution to flood prevention.