Climate Change and Distribution of Date Palms Figure 9. The climate (EI) for P. dactylifera in current time and projected using CLIMEX under the MIROC-H GCM running the SRES A2 scenario and for 2030, 2050, 2070 and 2100 for Australia and China. doi:10.1371/journal.pone.0048021.g009 stress is currently the main limiting factor in Canada, most parts of the United States (excluding Florida and California), Peru, Chile, and Ecuador, south-eastern Australia and most areas of China (Figures 7, 8 and 9). The same results were found for central to western Mali as a consequence of heat stress, which imposes a significant limitation for date palm establishment. Additionally, due to wet stress, P. dactylifera cannot be successfully grown in areas of eastern South America, such as central Guatemala, Colombia, Uruguay, and southern Chile, nor in parts of southern Africa including Angola, Zambia, Zimbabwe, and northern Madagascar. Wet stress also causes Germany, Poland, Ireland, northern Portugal, Azerbaijan, Georgia, southern India, Thailand, Burma, Bhutan, eastern Nepal, Spain and southern eastern Australia to be unsuitable for the establishment of this species. Thus, cold and wet stresses impose significant limitations for expanding the global distribution of date palm in 2030 and beyond. The current and projected distribution of cold and wet stresses can be seen for selected regions in Figures 10 and 11, respectively. In the United States, the cold and wet stresses shift northward, meaning there may be larger areas available that are not affected by the aforementioned stresses and therefore more are conducive to date palm cultivation. Our modeling showed that cold and wet stresses will no longer be the limiting factors in large parts of the United States. Discussion Suitable climatic areas for P. dactylifera under present and future climate scenarios using CLIMEX were modeled in this study. The differences in the outcomes from the two GCMs emphasize the uncertainties associated with the state of climate modeling associated with greenhouse emission patterns [14]. It is clear that different models may produce different results. It should also be highlighted that suitability projections are only potential distribu- tions based on climatic factors and not predicted future distributions [14]. Thus, it is highly recommended that any projection of future suitable areas based on CLIMEX should also incorporate non-climatic factors such as land-use type, soil type, soil drainage and soil-nutrients [11]. Here, our model provided a good fit to the present global distribution records of date palm on the southern coast of Mexico and south-western North America, regions that were used to validate the model. In this study, both CS and MR GCMs projected that in the Americas, some regions including the south-western coast of Mexico and North America, eastern Brazil, south-eastern Bolivia, northern Venezuela, Cuba, northern Colombia and Paraguay will become more climatically suitable towards 2100. However, the MR GCM projected Florida becoming more climatically suitable than the CS GCM between 2030 and 2100 due the projection of a greater increase in temperature and smaller decrease in the amount of rainfall in the MR GCM [46,47]. Thus, date palms PLOS ONE | www.plosone.org 9 October 2012 | Volume 7 | Issue 10 | e48021