Southwestern white pine (Pinus strobiformis) species distribution models project a large range shift and contraction due to regional climatic changes

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<p>Southwestern white pine (Pinus strobiformis; SWWP) is a conifer species that occurs at mid to high elevations in<br />the mountains of Arizona, New Mexico, and northern Mexico. A key component of mixed conifer forests in the<br />region, SWWP is an important species for wildlife and biodiversity. The dual threats of the non-native fungal<br />pathogen that causes white pine blister rust (WPBR) and a warmer, drier projected future climate have created<br />an uncertain future for SWWP. In this study, we used a novel multi-scale optimization approach including an<br />ensemble of four species distribution modeling methods to explore the relationship between SWWP occurrence<br />and environmental variables based on climate, soil, and topography. Spatial projections of these models reflecting<br />the present climate provide an improved range map for this species that can be used to guide field data<br />collection and monitoring of WPBR outbreaks. Future projections based on two emissions scenarios and an<br />ensemble of 15 general circulation models project a large range shift and range contraction by 2080. Changes in<br />the future distribution were particularly extreme under the higher emissions scenario, with a more than 1000 km<br />northerly shift in the mean latitude and 500m increase in the mean elevation of the species’ suitable habitat.<br />This coincided with a range contraction of over 60% and a significant increase in habitat fragmentation. The<br />ability of SWWP to realize its projected future range will depend on colonization at the leading edge of the range<br />shift, including dispersal dynamics, resistance to WPBR, competition with other species, and genetic adaptations<br />to local climate. Our results provide information that can be used to guide monitoring efforts and inform conservation<br />planning for this keystone species.</p>