Ecological Niche Modeling of Influential Minnesota Mammals since the Last Glacial Maximum
Ecological niche modeling (ENM) aims to project species distributions into paleoclimate or future climate conditions by replicating the relationships between species and the climate conditions they currently inhabit. ENMs were created for six fundamental Minnesotan species to show their changing distributions across North America from the Last Glacial Maximum (21 ka) to current climate conditions (1979-2013 avg.). These 6 species are the wolf (Canis lupus), the Eastern gray squirrel (Sciurus carolinesis), the American beaver (Castor canadensis), the American bison (Bison bison), the North American river otter (Lontra canadensis), and the American moose (Alces americanus). These species were selected because of their unique ecological niches and influence on Minnesota ecosystems.
The models were created using species occurrences from the GBIF and iDigBio databases, Maxent software, and 19 bioclimatic variables for each time period from PaleoClim. Each model was trained by using up to 7,000 species occurrences to identify habitable bioclimatic conditions in today’s climate, which then got projected into paleoclimate conditions to model each species’ paleo-distribution. The results show that all six species’ distributions increased significantly in size and shifted northward from the Last Glacial Maximum to today. These models account only for environmental conditions' influence on a species' distribution. Some species, such as C. lupus and B. bison, have undergone great reductions in populations and range due to human influence which is not reflected in these models. Understanding how species have reacted to natural climate change in the past is critical to understanding how species will react to anthropogenic climate change.