Abstract
Our objectives were to predict and map the climatic niche for Pinus leiophylla for a period of normalization (years 1961-1990) and future (2030, 2060 and 2090) climates, and to suggest management strategies to accommodate climate changes, and discuss implications for conservation. A bioclimate model predicting the presence or absence of P. leiophylla (lumped with its putative variety P. leiophylla var. chihuahuana ) was developed by using the Random Forests classification tree on Mexican and Unites States of America forest inventory data. The bioclimatic model had an average error of prediction of 4.6 %. The model used six predictor variables, dominated by precipitation variables. Projecting the 1961-1990 climate niche into future climates provided by three general circulation models and two greenhouse-effect gas emission scenarios, suggested that the area occupied by the niche should diminish rapidly over the course of the century: a decrease of 35 % by the decade surrounding 2030, 50 % for 2060, and 76 % for 2090. The most serious habitat reduction occurs at both latitudinal extremes of the species distribution: Chiricagua Mountains, Arizona, Unites States of America in the northern extreme, and at Oaxaca State, Mexico, in the southernmost extreme. There is no indication at all of expansion of suitable climatic habitat northwards. We urge establishing seed banks encompassing seed from provenances sampled from the largest part possible of the natural distribution, and start assisted migration tests, to realign the natural populations with the climate for which they are adapted and that will occur at higher altitudes.