Forest expansion in Cypress Hills Interprovincial Park

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The distributions of forests and grasslands in semi-arid regions are changing, both locally and globally, as a result of fire, drought, livestock grazing, and other factors. In Canada, shifts between these two vegetation types are particularly notable in Cypress Hills Interprovincial Park, a 400 sq. km protected area straddling the southern Alberta-Saskatchewan border. The park is situated on an elevated plateau within the Prairies, and contains a mixed landscape of rough fescue grassland and forests dominated by lodgepole pine, trembling aspen, and white spruce. Over the past century trees and forests have expanded into former grassland areas, reducing overall biodiversity and the amount of forage available to cattle. Working in partnership with park agencies in both Alberta and Saskatchewan, this project will characterize how and where forest expansion is occurring across Cypress Hills. Using field data and historical aerial photographs, we will determine whether the rate of forest expansion has changed across multiple time periods (1970s-1990s; 1990s-2010s), which characteristics of the physical environment are most strongly associated with forest expansion, where the risk of further land cover change is highest, and what factors are expected to limit the rate of forest expansion in the future. Our findings will be incorporated into new management plans that set out specific objectives related to the maintenance of grassland and forest cover. Park managers may prescribe new vegetation management practices or changes to grazing activity if forest expansion is expected to adversely impact ecosystem functions and services over time, including ecosystem diversity, carbon sequestration, and the provision of forage. The research will provide specific benefits to park managers, cattle producers, and visitors in Cypress Hills, as well as more general benefits related to biodiversity conservation and carbon sequestration for Canadians everywhere.