CLIMATIC ADAPTABILITY AND RESILIENCY OF NORTH AMERICAN SAGEBRUSH-STEPPE MAMMALS AND BIRDS

Katherine Burgstahler

doi:10.7273/000007330

Climate change and changing rates of extreme events are altering species distributions. In the Columbia Basin sagebrush (Artemesia spp.) ecoregion of Washington, the intensity, frequency, and extent of wildfire has increased drastically over the last few decades. Wildfire on this landscape, already modified and fragmented by agriculture and other disturbances, may challenge the persistence of wildlife that depend on continuous shrublands and grasslands. Therefore, we examined how fire and habitat characteristics of sagebrush patches influence the distribution of sagebrush-associated, grassland-associated, and generalist mammals and birds across the Columbia Basin. Over four spring-summer field seasons (2021-2024), we surveyed 155 burned and unburned sagebrush sites using a combination of camera traps, avian point count surveys, and vegetation surveys. From these data, we assessed how recent (within 20 years of survey) fire and habitat characteristics affect the site use and abundance of wildlife using occupancy models and generalized linear models. We documented 22 avian and mammalian species during camera trap surveys and 77 avian species during point counts. Despite documenting many species within burned sites (86), we found sagebrush-associated passerines and several other species at higher abundances in unburned sites. Within burned patches, fire age, annual grass cover, and forb cover were important drivers of site use and abundance, and responses to fire and habitat characteristics varied among taxa and degree of specialization. Our findings will guide stakeholders when making short-term modifications to post-fire sagebrush habitat and long-term planning decisions related to fire resiliency for Columbia Basin mammals and birds. Climatically suitable space is shifting poleward and up in elevation for many species. However, the ability of species to track shifting climatic conditions will depend on future anthropogenic land-use patterns. These concerns are particularly important for species inhabiting biomes with substantial historic and expected future land-use changes. Here, we examined changes in suitable space for 11 sagebrush-associated wildlife species inhabiting the highly modified sagebrush-steppe biome of western North America and determined the potential for the Columbia Basin ecoregion (located in the northwest of the biome) to serve as a climatic refugia. We developed climate-based species distribution models of focal species and projected those models under a moderate climate scenario in two future time periods. We used two future land- cover scenarios to calculate the amount of optimal space (suitable climate and land cover) in the Columbia Basin and the intersection of optimal space with currently protected lands. Climatic suitability increased for raptors but decreased for grouse and herbivores in their current range, and the Columbia Basin increased in or retained climatic suitability for most species. Our results support that the Columbia Basin may be a promising climate refugia, especially for two species projected to have increasing optimal space in both land-use scenarios. Finally, protected areas within the Columbia Basin generally cover areas with high overlap of optimal space for species. We provide methods that leverage open-source databases and can be transferred to identify future suitability trends for other species, climate refugia within biomes, and priority areas for biodiversity conservation in other systems.

CLIMATIC ADAPTABILITY AND RESILIENCY OF NORTH AMERICAN SAGEBRUSH-STEPPE MAMMALS AND BIRDS

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