Monitoring an ecosystem at risk: What is the degree of grassland fragmentation in the Canadian Prairies?

Laura Roch, Jochen A. G. Jaeger

Increasing fragmentation of grassland habitats by human activities is a major threat to biodiversity and landscape quality. Monitoring their degree of fragmentation has been identified as an urgent need. This study quantifies for the first time the current degree of grassland fragmentation in the Canadian Prairies using four fragmentation geometries (FGs) of increasing specificity (i.e. more restrictive grassland classification) and five types of reporting units (7 ecoregions, 50 census divisions, 1,166 municipalities, 17 sub-basins, and 108 watersheds). We evaluated the suitability of 11 datasets based on 8 suitability criteria and applied the effective mesh size (m(eff)) method to quantify fragmentation. We recommend the combination of the Crop Inventory Mapping of the Prairies and the CanVec datasets as the most suitable for monitoring grassland fragmentation. The grassland area remaining amounts to 87,570.45 km(2) in FG4 (strict grassland definition) and 183,242.042 km(2) in FG1 (broad grassland definition), out of 461,503.97 km(2) (entire Prairie Ecozone area). The very low values of m(eff) of 14.23 km(2) in FG4 and 25.44 km(2) in FG1 indicate an extremely high level of grassland fragmentation. The m(eff) method is supported in this study as highly suitable and recommended for long-term monitoring of grasslands in the Canadian Prairies; it can help set measurable targets and/or limits for regions to guide management efforts and as a tool for performance review of protection efforts, for increasing awareness, and for guiding efforts to minimize grassland fragmentation. This approach can also be applied in other parts of the world and to other ecosystems.