Colonial management drives ecological change following exclusion of Indigenous stewardship in a Stoney Nakoda montane grassland, Canadian Rocky Mountains

Background/Question/Methods

In the Canadian Rocky Mountains, landscape patterns have changed dramatically over the last 150 years. Traditional Indigenous burning practices had kept Rocky Mountain landscapes open, diverse and productive for millennia. Management transitions shift landscape vegetation patterns, and areas previously stewarded by Indigenous Peoples are undergoing successional change. In a montane valley of the Stoney Nakoda Nations, we hypothesized that Indigenous burning practices maintained open grasslands and an abundance of early-seral species. Under current Kootenay Plains Ecological Reserve and provincial management regimes, we predicted a successional transition from grasslands to shrub-dominated and forested areas, with the decline of culturally important forbs. Using oblique photographs taken in 1924 paired with 2021 satellite imagery, we compared past and present landscape vegetation cover and quantified landscape succession. We then tested the role of management on grassland retention, and the role of environmental variables on vegetation succession. At the plot level, we examined differences in vegetation class cover and plant community structure between surveys conducted in 1981, 1995 and 2020.

Results/Conclusions

Nearly half (47%) of the landscape surveyed showed seral progression in vegetation class which was not explained by topography, geology, or climate warming under a binomial regression framework. Grassland area decreased four-fold between 1924 and 2021; grassland retention was strongly related to management zoning with greater losses in the Ecological Reserve than on lands under Stoney Nakoda management. Indigenous burning practices in montane areas produce patterns of small open areas; hundreds of small patches have disappeared on the present landscape. Vegetation plots surveyed in 1981, 1996, and 2020 in the Kootenay Plains Ecological Reserve reveal changes to vegetation class, plant community composition and culturally important forbs. In plots previously composed largely of forbs and graminoids (mean cover of 35% and 32 %), shrubs have become the dominant groundcover (increase from 0.4% cover to 32% cover). Declines in historic vegetation include a loss of culturally important food and medicine plants to the Stoney Nakoda Nation. A weight of evidence approach suggests these results follow a removal of Indigenous Peoples and stewardship from the landscape. We demonstrate that the past century of colonial environmental management has altered ecological processes that were maintained on this landscape for millennia by Indigenous stewards.