Predicted Shifts in Small Mammal Distributions and Biodiversity in the Altered Future Environment of Alaska: An Open Access Data and Machine Learning Perspective

Abstract

Climate change is acting to reallocate biomes, shift the distribution of species, and alter community assemblages in Alaska. Predictions regarding how these changes will affect the biodiversity and interspecific relationships of small mammals are necessary to pro-actively inform conservation planning. We used a set of online occurrence records and machine learning methods to create bioclimatic envelope models for 17 species of small mammals (rodents and shrews) across Alaska. Models formed the basis for sets of species-specific distribution maps for 2010 and were projected forward using the IPCC (Intergovernmental Panel on Climate Change) A2 scenario to predict distributions of the same species for 2100. We found that distributions of cold-climate, northern, and interior small mammal species experienced large decreases in area while shifting northward, upward in elevation, and inland across the state. In contrast, many southern and continental species expanded throughout Alaska, and also moved down-slope and toward the coast. Statewide community assemblages remained constant for 15 of the 17 species, but distributional shifts resulted in novel species assemblages in several regions. Overall biodiversity patterns were similar for both time frames, but followed general species distribution movement trends. Biodiversity losses occurred in the Yukon-Kuskokwim Delta and Seward Peninsula while the Beaufort Coastal Plain and western Brooks Range experienced modest gains in species richness as distributions shifted to form novel assemblages. Quantitative species distribution and biodiversity change projections should help land managers to develop adaptive strategies for conserving dispersal corridors, small mammal biodiversity, and ecosystem functionality into the future.

Fig 1. Study area map.

Depiction of the study area composed of the state of Alaska. Ecoregion boundaries are shown for reference.

Fig 2. Varclus correlation tree.

Projected 2100 community arrangements for 17 species of small mammals in Alaska based on a varclus correlation analysis in R. Brackets aggregate species into 2100 community groups, while colors indicate species membership in 2010 community groups.

Fig 3. Distribution change maps.

Predicted distribution change for each of the 17 modeled species of small mammal in Alaska: a) northern red-backed vole (Clethrionomys rutilus), b) northern collared lemming (Dicrostonyx groenlandicus), c) brown lemming (Lemmus trimucronatus), d) long-tailed vole (Microtus longicaudus), e) singing vole (M. miurus), f) root vole (M. oeconomus), g) meadow vole (M. pennsylvanicus), h) yellow-cheeked vole (M. pennsylvanicus), i) cinereus shrew (Sorex cinereus), j) pygmy shrew (S. hoyi), k) montane shrew (S. monticolus), l) American water shrew (S. palustris), m) tundra shrew (S. tundrensis), n) barren-ground shrew (S. ugyunak), o) Alaska tiny shrew (S. yukonicus), p) northern bog-lemming (Synaptomys borealis), q) meadow jumping mouse (Zapus hudsonius). Red = areas of distribution loss, green = areas of distribution gain, and yellow = areas of persistence.

Fig 4. Species richness change maps.

Predictive species richness maps based on composites of binary (presence/absence) maps for 17 species of small mammals for the years a) 2010 (modified from [39]; S1 File) and b) 2100. Maps also depict net change in c) species richness (ΔBio) and d) relative indices of occurrence (ΔRIO). Warm colors indicate net gains in RIO (relative index of occurrence) and species richness, whereas cool colors indicate net loss of RIO and species richness.

Fig 5. Species richness graphs.

Histograms depicting the frequency of pixels for the number of species in a) 2010, b) 2100, as well as the net change in c) species richness, and d) relative indices of occurrence.