Characterizing the contribution of Alberta's grazing lands to large scale structural connectivity

Background/Question/Methods

Across the prairie region of Canada, beef cattle producers are stewards of vast grassland areas and pastures with perennial vegetation cover. These areas potentially play a significant role in maintaining biodiversity and landscape connectivity. Therefore, avoiding the conversion of grassland, e.g., to annual crops, is important for biodiversity management and aligns with land trust stewardship priorities. Here, we aim to (1) quantify the contribution of grazing lands kept through practicing extensive beef production systems to structural landscape connectivity; and (2) determine how the conversion of these grazing lands to annual crops could impact structural landscape connectivity across multiple spatial scales in Alberta, Canada. We modeled structural landscape connectivity with a species-agnostic approach, where landscape resistance to organism movement (ecological flow) is inversely related to the degree of naturalness of landcover types. Specifically, we modeled connectivity as omnidirectional current density. We then calculated the mean current density per county in Alberta to quantify its contribution to large-scale connectivity across the province. We assessed the percent change in mean current density per county between the current land-use map and a scenario where all grazing lands, which are currently preserved through extensive beef production systems, were converted to annual crops.

Results/Conclusions

We found that in counties with large amounts of grazing lands, their conversion to annual crops would result in a decrease in the mean current density. This could be attributed to the reduction in areas of natural land-covers that are permeable to ecological flow. This conversion scenario created new pinch-points in the southeast part of the province. These are areas where ecological flow is severely restricted by human land-use and funneled through a narrow path with lower resistance compared to the surroundings. Interestingly, in parallel, this caused an increase in the mean current density of areas with little or no grazing lands, such as the Rocky Mountains and the Boreal Forest areas, which may be due to the redirection of the current flow between natural regions. These results illustrate the importance of grazing lands kept through practicing extensive beef production systems for maintaining structural landscape connectivity across the agricultural areas of Alberta and its repercussions across the province.