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Objectives: Species with a restricted distribution in isolated populations are the most threatened under climate change. Chihuahua spruce (Picea chihuahuana Martinez) is one of those species. The analyses of past and present environmental conditions where these species have occurred allow us to understand the dynamics of their distribution. Therefore, projecting the results to the future under different climatic scenarios provides a basis for conservation purposes. The objective of this study was to evaluate the influence of climatic variables on the availability of suitable habitat for P. chihuahuana under paleoclimatic, current and future scenarios.

Methods: Paleoclimate data for the Last Glacial Maximum (LGM similar to 22,000 years BP), Holocene Medium (HM similar to 6000 years BP) and climatic data from the 1950-2000 periods were derived from CCSM4 and MIROC-ES models. Carbon dioxide concentration for 2050 and 2070 were derived from CCSM4 y HadGEM2-ES models under four levels of forcing. Data for the different time periods was subjected to the MaxEnt program.

Results: The species distribution models showed a good fit with values of AUC> 0.99 for all time periods. Since the LGM, the potential habitat for P. chihuahuana has been declining, most likely due to global warming. Currently, human activities have exacerbated this decline. Climatic variables that most contributed to the models of suitable habitat were the lowest temperature of the coldest month (Bio6), the precipitation of the coldest quarter (Bio19), the precipitation of the warmest quarter (Bio18), and the annual average temperature (Bio 1). Future scenarios predict a reduction of suitable habitat for P. chihuahuana, or even its disappearance.

Conclusions: Projections into the future locate possible micro refuges under some climatic change scenarios; however, under the highest atmospheric greenhouse gases scenario, suitable habitats for this species will disappear. Depending upon the response by humans to mitigate climatic change, P. chihuahuana may persist longer in those micro refuges, either naturally or with assisted transplanting. On the other hand, if there are no actions to reduce GHG, it is futile to develop conservation programs because there will be no suitable habitat for this species, and it will become extinct. (C) 2019 The Authors. Published by Elsevier B.V.