Net change in grassland landcover and conservation implications for grassland birds in Ontario, Canada

In North America, grassland bird populations have declined more steeply over the past half-century than birds breeding in any other biome. Grassland bird populations are declining in part due to habitat loss from changes in land use, including conversion to row crops, urban development, and energy development. We assessed changes in grassland landcover (primarily agricultural) over a recent 8 year period across southern Ontario, Canada. We (1) quantified net change (loss and gain) of grassland landcover, (2) identified primary landcover types converted from and to grassland, (3) assessed potential ecological and economic drivers of net change in grassland landcover, and (4) assessed how grassland loss and net change in grassland related to changes in abundance of three grassland bird species. We selected the best-supported general linear model quantifying relationships between ecological and economic factors and net change in grassland landcover. Based on Annual Crop Inventory data, the net area of grassland decreased by 18% from 2011 to 2019. Grassland was most frequently converted to oilseed (primarily soybean), urban landcover, and broadleaf forest. The best predictor of net change in grassland landcover over the 8 year period was the amount of natural landcover (e.g., forest, shrubland, wetland) in the landscape at the beginning of the period, which had a positive association, resulting in smaller losses and gains in some areas. Additional predictor variables in the best-supported model included: urban cover, distance to road, soil quality for agricultural production, land price, beef price, and corn price. However, statistical relationships between net change in grassland landcover and predictor variables were weak (adjusted R2 of the best-supported model was 0.09). Regional changes in relative abundance of Bobolinks (Dolichonyx oryzivorus), Eastern Meadowlarks (Sturnella magna), and Savannah Sparrows (Passerculus sandwichensis) were not correlated with grassland loss or net change in grassland across a 27 km grid. Although we identified some factors associated with net change in grassland landcover, relationships were weak, suggesting future research is needed to identify primary drivers of net change in grassland landcover to inform strategies to maintain and enhance breeding habitat for grassland birds in Ontario.