Using ArcGIS’s Habitat Suitability Model tool, models were developed to understand how the suitability of big sagebrush habitat will change under different climate-warming scenarios. A model based on the current distribution of big sagebrush was developed using five abiotic environmental variables, including temperature and precipitation. The model was rerun with climate projection data of future temperature and precipitation conditions in 2080 to determine how habitat suitability for the plant will change. Overall, the results agreed with my initial predictions. It was found that areas currently inhabited by big sagebrush will generally become less suitable under more extreme warming conditions and that regions beyond the northern edge of the range will become more suitable as cold stress is alleviated.

There are several limitations to the project that likely influenced the results. First, the projected didn’t account for any biological factors that may be influencing the species’ range. Only abiotic factors, such as elevation, temperature, and precipitation were evaluated. Biotic and ecological factors such as predation, competition, disease, pollination, and dispersal were all ignored. While some of these factors may be influential on the species’ range, there is little data that can be utilized to account for them in a GIS project. Understanding how the species’ range is controlled by different biotic interactions would require transplant experiments that exclude these biotic interactions (e.g., using mesh exclosures to prevent predation on some plants and observing how fitness changes). Without such information, it is impossible to conclude how interactions between big sagebrush and climate warming will be altered by other biological factors.

A second limitation is that the project didn’t account for occurrences across the entire range of big sagebrush, as it only focused on populations within British Columbia. Plants in southern parts of the range (e.g., Baja California) likely have a higher thermal optimum than plants in British Columbia. If the big sagebrush plants in B.C. have a higher thermal optimum more similar to their southern counterparts (which may be possible if little local adaptation has occurred in B.C.), there may be different results in the projected outcomes of habitat suitability. For example, the plant’s highest occupied mean annual temperature in B.C. was 10.6˚C. However, plants in Oregon and California likely have higher thermal tolerances (i.e., greater than 10.6˚C) that would have influenced the data utilized for the fuzzy transformation. However, using only British Columbian occurrences was an acceptable simplification for the project, as capturing the entirety of the range would have required a synthesis of many data sources from different jurisdictions and would have required much higher processing power to perform the same analysis. Additionally, this step was justified because it was assumed that local adaptation has occurred and that the plants in B.C. are the northernmost populations that would undergo important range shifts. Field work and genetic analysis would be needed to understand the extent to which big sagebrush populations across the range are evolutionarily related.

Understanding the extent to which organisms can and will undergo range shifts under climate warming is a vitally important ecological and conservation question. This project represents a method of examining how habitat suitability changes under these novel conditions. Additionally, analyses like this could be used to inform assisted migration – a technique by which plants are manually transplanted to northern or higher-elevation regions to ensure that the species can continue surviving under climate warming (Hewitt et al., 2011). Models such as this could easily be expanded to include more variables and more species, creating quantifiable predictions of habitat changes. It is our responsibility to be stewards of the ecosystems on our planet, and understanding the impacts that humans are having on the natural world is the first step towards protecting it.