Conservation of threatened vascular plants in intensive agricultural landscapes in Canada

Deep in the Canadian province of Saskatchewan, a fifteen-year botanical detective story has revealed a hidden crisis unfolding across one of the most heavily modified agricultural landscapes in the country. A comprehensive study of the Redberry Lake Biosphere Region, published in the journal Nature Conservation, has identified 46 threatened vascular plant taxa surviving in scattered fragments of their former habitat, many of them documented there for the very first time. The findings expose a stark paradox: the zones of a UNESCO biosphere reserve specifically designated for biodiversity protection hold fewer threatened plant species than the surrounding transition area, where conservation is not the primary goal.

The research, conducted by botanist V. Kricsfalusy through systematic field surveys spanning 2010 to 2025, represents one of the most detailed inventories of rare plants ever assembled for a Canadian biosphere region. The Redberry Lake Biosphere Region, designated by UNESCO in 2000 and expanded five-fold from its original 112,000 hectares to roughly 700,000 hectares today, sits on the northern boundary of the Great Plains of North America. It straddles two biomes, the Prairie and Boreal Plain ecozones, encompassing the Aspen Parkland and Boreal Transition ecoregions. Less than 20 percent of the original grassland habitat remains in Saskatchewan, and only 9.8 percent of the province is protected or conserved through various means, making the region a critical refuge for plants on the edge.

The taxonomic results are striking. Of the 46 threatened taxa, comprising 31 species, 5 subspecies and 10 varieties across 19 families and 34 genera, an overwhelming 78.3 percent were recorded in the biosphere region for the first time. The most species-rich families are the orchids (Orchidaceae, with 9 taxa), the sedges (Cyperaceae, with 8), and the grasses (Poaceae, with 4). Among genera, Carex, Cypripedium, and Potentilla make the largest contribution. These 46 taxa represent approximately 7.9 percent of the region’s native flora of 584 taxa, which in turn accounts for about 42.1 percent of Saskatchewan’s entire flora.

Spatial analysis revealed a highly uneven distribution. The majority of species occurrences and richness hotspots are concentrated in the Aspen Parkland ecoregion of the Prairie ecozone. Within that ecoregion, the Hafford Plain ecodistrict recorded the highest number of occurrences, with 153 records across 20 species and a median of 7.65 occurrences per sampling unit. The Whitewood Hills followed with 81 records across 23 species. In the Boreal Plain ecoregion, threatened plants were far less frequent, with the Witchekan Plain showing the highest presence of 9 species. No species at all were recorded in the Meeting Lake Upland and Onion Lake Plain ecodistricts.

Perhaps the most alarming technical finding concerns the extreme rarity of most populations. Out of 1,917 grid cells of 2 by 2 kilometres that make up the region, threatened plants were recorded in only 52, or 2.7 percent of all cells. The majority of species, 34 taxa or 73.9 percent, have just 1 to 5 occurrences. When assessed by Area of Occupancy, 78.3 percent of species were found in only 1 to 3 grid cells. The most widely represented species, Cypripedium parviflorum var. pubescens with 32 occurrences and Almutaster pauciflorus with 30, together account for nearly a third of all documented occurrences. The analysis identified seven richness hotspots with more than five threatened species each, but three of them, at Muskeg Lake, Martins Lake, and Borden Dunes, lie outside the core area and buffer zone designated for biodiversity protection.

Population sizes are similarly skewed toward the small classes. Most threatened plants exist in populations of 1 to 11 individuals, with only seven species containing 51 to 100 individuals. Botrychium campestre var. campestre is known from a single recorded individual, occurring at the northern limit of the species’ North American range. In contrast, Festuca hallii is frequently found in large patches exceeding 1,000 individuals. Small population size is often the direct consequence of recent habitat loss from human activities, though it can also reflect the life strategy of highly specialized organisms restricted to patchy habitats. These small populations exhibit structural and functional disorders including incomplete age spectra, limited potential for self-renewal, and low viability.

Habitat affinity analysis showed that almost half of all threatened plants, 21 species or 45.7 percent, are found in wetlands, particularly moderate-rich fens, marshes and wet meadows. Grassland, sandy, and woodland habitats together account for 17 species. Given that wetlands occupy a substantially smaller portion of the landscape than grasslands, the proportion of threatened plants concentrated there is disproportionately high. In terms of growth form, threatened species belong mostly to herbs (63 percent) and graminoids (28.3 percent), while trees, shrubs, and vines are completely absent from the threatened flora.

The threat assessment identified habitat loss and successional overgrowth as the two most severe pressures, together affecting 22 species or 47.8 percent. Habitats of Cypripedium parviflorum var. pubescens, Botrychium campestre var. campestre, and Corallorhiza striata var. striata are particularly vulnerable to encroachment of woody species during natural succession. Invasive alien species, many introduced with seed crops, livestock feed, or forage plantings, affect eight threatened plants and continue to spread through roadsides and disturbed areas, a process likely to accelerate under climate change. Wetland interventions and recreational land use each target six species. Cypripedium parviflorum var. pubescens faces the most extreme situation, confronting four simultaneous threats.

Conservation status rankings under NatureServe criteria at the subnational level reveal two taxa as S1, Critically Imperiled, seven as S2, Imperiled, and 37 as S3, Vulnerable. Five species are assessed at the national level as N3 and two at the global level as G3. Two S3 species, Cypripedium passerinum and Liparis loeselii, are simultaneously ranked as Vulnerable and Near Threatened under IUCN criteria. In an unexpected twist, two apparently secure species, Fraxinus pennsylvanica and Ulmus americana, are ranked as Critically Endangered and Endangered respectively under IUCN criteria, reflecting global declines of ash and elm from disease and habitat loss.

The gap analysis delivered the study’s most consequential recommendation. The core area holds 64 occurrences of 12 species and the buffer zone 156 occurrences of 19 species, while the transition area contains 123 occurrences of 35 species, meaning the zones designated for biodiversity protection together hold fewer threatened species than the transition area alone. The authors propose establishing Important Plant Areas in the buffer zone to safeguard calcareous fens and meadow marshes, and recognising other effective area-based conservation measures in the transition area, along with micro-reserves and small-scale plant-protected areas. Active management including conservation grazing, clearing, prescribed fire, and invasive species control is needed in the majority of threatened plant habitats. These strategies, the study concludes, are essential for raising public awareness and prompting political action, but smaller-scale interventions by local practitioners remain equally vital for preventing local extinction in a landscape where agriculture has transformed nearly everything.

Subject of Research: Conservation of threatened vascular plants in intensive agricultural landscapes in Canada

Article Title: Conservation of threatened vascular plants in intensive agricultural landscapes in Canada

Article References: Kricsfalusy, V. (2026). Conservation of threatened vascular plants in intensive agricultural landscapes in Canada. Nature Conservation, 63, 37-57. https://doi.org/10.3897/natureconservation.63.177517

Image Credits: AI Generated

DOI: 10.3897/natureconservation.63.177517

Keywords: Conservation, threatened, vascular, plants, intensive, agricultural, landscapes, Canada, scientific research