Climate Change and Distribution of Date Palms Figure 10. Comparison of the location of cold stress in some selected regions for date palm growth between current time and 2100. These areas were selected on the basis of large changes in cold stress in the future. doi:10.1371/journal.pone.0048021.g010 would not suffer any wet or cold stress in Florida. A comparison between these two models also indicated that, based on the MR GCM, more regions in western Argentina may be suitable for date palm growth compared to the CS projection (Figures 4 and 7). A comparison between the results of CS and MR GCM for southern Africa indicated that P. dactylifera ranges appeared to shift further inland in the future. However, the CS GCM projected that most regions in Angola may be climatically suitable by 2100, but, based on MR GCM, this suitability may be limited to the southern and coastal regions due to an increase in the wet stress in northern and eastern Angola (Figures 5 and 8). There were some divergent results in the projection of suitable areas for date palms in North Africa and Middle Eastern countries between the CS and MR GCMs. For example, both models projected that northern Algeria, Morocco, Western Sahara, Tunisia, northern Egypt, Somalia and Kenya may become climatically suitable for P. dactylifera. Furthermore, both models projected that southern Algeria, eastern Mauritania, northern Mali and western Chad may become unsuitable for this species. In contrast, the CS model projected that by 2100, Mali, Niger, Chad and most parts of Sudan may not be suitable for date palm, while the MR model projected that southern Mali and Niger, eastern Chad and western Sudan may remain climatically suitable for date palms by 2100 (Figures 5 and 8). There were some agreements and disagreements in projection of suitable areas for date palm growth in North Africa and Middle Eastern countries between CS and MR GCMs. For example, both models projected that northern Algeria, Morocco, western Sahara, Tunisia, northern Egypt, Somalia and Kenya may become climatically suitable for P. dactylifera growth. Furthermore, both models projected that southern Algeria, eastern Mauritania, northern Mali and western Chad may be unsuitable for this species. On the other hand, the CS model projected that by 2100, Mali, Niger, Chad and most parts of Sudan may become unsuitable for date palm growth since the MR model projected that southern Mali and Niger, eastern Chad and western Sudan may remain climatically suitable for date palms growth by 2100 (Figures 5 and 8). From the results (Figures 10 and 11), it is evident that currently unsuitable areas such as the western United States, southern Mexico, northern and southern Africa, may become suitable climatically by 2100 through decreasing cold and wet stresses. Iran, Turkey, and Spain are some examples where cold stress may decrease by 2100 (Figure 10). Figure 11 illustrates that wet stress in northern Gabon and eastern Quebec may decrease over the next few decades. The results of the climate change modeling provide an indication of the possible change in the potential future distribution of P. dactylifera. As the climate changes, some areas where P. dactylifera currently occurs may become climatically unsuitable, and as a consequence, the economies in those areas may decline. For example, it was reported that Algeria and Saudi PLOS ONE | www.plosone.org 10 October 2012 | Volume 7 | Issue 10 | e48021