Climate Change and Distribution of Date Palms Figure 7. The climate (EI) for P. dactylifera in current time and projected using CLIMEX under the MIROC-H GCM GCM running the SRES A2 scenario and for 2030, 2050, 2070 and 2100 for the North and South America continent. doi:10.1371/journal.pone.0048021.g007 East. The lower (SM1) and upper (SM2) optimum moisture thresholds were set at 0.013 and 0.81, respectively, to improve species growth in Egypt, Saudi Arabia, Iran, India, and some countries in Africa [11]. The upper soil moisture threshold (SM3) was set at 0.9 because this species and its fruit can be negatively affected by high soil moisture [11]. Additionally, this value provided an appropriate fit to the observed distribution. All CLIMEX parameters are summarized in Table 1. Results Current Climate The present distribution of native and cultivated P. dactylifera is illustrated in Figure 1. A comparison between the modeled global climate appropriateness (Figure 2) with the recognized distribution of this species showed that there was a good match between the Ecoclimatic Index resulting from the CLIMEX model and the current distribution of P. dactylifera. The modeled results indicated that the western areas of the United States, western Mexico, southeast Spain, Morocco, Portugal, central Sudan, Egypt, eastern Mozambique, central and western United Arab Emirates, southern Iran, eastern Pakistan and large parts of Australia have suitable climatic conditions for P. dactylifera. Although large parts of central southern Africa were modeled to have suitable climatic conditions for P. dactylifera in its current known distribution, limited data were available from these regions. This could be due to a shortage of reports from these areas. Biotic factors such as competition or lack of dispersal opportunities could preclude this species from occurring in these areas. There is also a possibility that date palm has not been grown as an economically important crop in those regions. The current and potential distribution of P. dactylifera in North America, Mexico, and the Caribbean was used for model validation as shown in Figure 3. These regions were not used for model fitting. In Mexico and North America, the model projects much of the southern and south-western coast to be climatically suitable. There was a reasonably good fit between the model predictions and the actual recorded distribution data. Future Climate The results of the two global climate change models (GCMs) including CSIRO-Mk3.0 (CS) and MIROC-H (MR) with the A2 emission scenarios for the potential distribution of P. dactylifera for 2030, 2050, 2070 and 2100 are illustrated in Figures 4, 5, 6, 7, 8 and 9. For ease of discussion, the global distribution is subdivided into three regions: North and South America, Africa and Middle East, and Australia and South Asia. a) Results from CS model. In North and South America (Figure 4), the CS GCM projected much of the south-western coast of Mexico and North America, eastern Brazil, south-eastern Bolivia, northern Venezuela, Cuba, northern Colombia, and Paraguay to be more climatically suitable for P. dactylifera by 2030; this expansion steadily increased by 2050, 2070 and 2100. PLOS ONE | www.plosone.org 7 October 2012 | Volume 7 | Issue 10 | e48021