Figure 1. The current global distribution of P. dactylifera. doi:10.1371/journal.pone.0048021.g001 models only enable estimates of a species’ fundamental niche [15] while other reports show that it provides a spatial image of the realized niche [16,17]. CLIMEX has been widely used in many different applications [18]. Taylor [19] used CLIMEX for illustrating the potential distribution of Lantana camara L. by 2070. Yonow [20] employed CLIMEX for mapping the distribution of the Queensland fruit fly. Sutherst [21] applied the same software for modular modeling of pests. The susceptibility of both animal and human health to parasites under future climates has also been studied using CLIMEX [22]. Table 1. CLIMEX parameter values used for L. dactylifera modeling. Mnemonic Values Parameter Limiting low temperature Lower optimal temperature Upper optimal temperature Limiting high temperature Limiting low soil moisture Lower optimal soil moisture Upper optimal soil moisture Limiting high soil moisture Cold stress temperature threshold Cold stress temperature rate Heat stress temperature threshold Wet stress threshold Wet stress rate Heat stress accumulation rate doi:10.1371/journal.pone.0048021.t001 DV0 DV1 DV2 DV3 SM0 SM1 SM2 SM3 TTCS THCS TTHS SMWS HWS THHS 14uC 20uC 39uC 46uC 0.007 0.013 0.81 0.9 4uC 46uC 0.9 20.01 week21 0.022 week21 0.9 week21 Climate Change and Distribution of Date Palms As a consequence of climate change, the distribution of species like date palm will change [3]. It is essential to identify which regions will benefit by having the potential opportunity of cultivating date palms in the future and which may be adversely affected. Governments and agricultural organizations can prepare for this situation in advance and thereby gain significant economic advantages which can enable them to improve their economies. Alternately, regions that could be adversely affected can become aware of the situation and transition their economies. This awareness provides an opportunity to plan for alternative sources of income. With this aim, this study made use of the CLIMEX software package in developing a global model of the climate response of P. dactylifera based on its native and cultivated distribution. This model was then used to illustrate date palm potential distribution using two global climate models (GCM) including CSIRO-Mk3.0 and MIROC-H. These were run with the A2 SRES (Special Report on Emissions Scenarios) emission scenarios for 2030, 2050, 2070 and 2100. The A2 SRES was chosen with the assumption that, in the future, there would be high population growth coupled with slow economic growth and extensive technological change. Methodology CLIMEX Software CLIMEX is a modeling software package that basically operates on an eco-physiological growth model that assumes that species encounter favorable and unfavorable seasons. Growth is maxi- mized during favorable seasons and minimized during unfavorable seasons [23–25]. A major criticism of CLIMEX is that it does not include biotic interactions and dispersal in the modeling process. However, other factors may be incorporated after the CLIMEX modeling has been performed using GIS and RS software [26]. The key assumption behind CLIMEX is that climate is the main determinant of the distribution of plants and poikilothermal animals [27]. CLIMEX enables the user to infer parameters that describe the species’ response to climate based on its geographic PLOS ONE | www.plosone.org 2 October 2012 | Volume 7 | Issue 10 | e48021