Climate Change and Distribution of Date Palms Figure 2. The Ecoclimatic Index for P. Dactylifera, modeled using CLIMEX for current climate. doi:10.1371/journal.pone.0048021.g002 range or phenological observations [23]. The Ecoclimatic Index (EI) is a general annual index of climatic suitability based on weekly calculations of growth and stress indexes. It is scaled from 0 to 100, and theoretically, species can establish if EI .0. In CLIMEX, the annual growth index (GIA) describes the potential for population growth during favorable climate conditions. The GIA index is determined from the temperature index (TI) and moisture index (MI) which represent the species’ temperature and moisture requirements for growth. The user can describe the probability of survival of the species during unfavorable conditions using four stresses: cold, heat, dry and wet. Therefore, based on available distribution data, this software was used to develop a model of the potential distribution of P. dactylifera under current and future climate scenarios. Distribution of Date Palms (P. dactylifera) The Global Biodiversity Information Facility (GBIF) [28] was used to gather information on P. dactylifera distribution and this information was supplemented by other date palm literature [8,12,14,28–41] (Figure 1). The GBIF database contained 583 records for P. Dactylifera; however, 342 records did not have geographic coordinates and were removed, leaving 241 records. Duplicate records were also removed. Thus, 163 records from the GBIF database and 49 records obtained from the literature review were used in parameter fitting. These 163 records were geo- graphically representative of the known distribution of date palms as shown in Figure 1. Climate Data, Climate Models and Climate Scenarios In this study, the CliMond 109 gridded climate data were used for modeling [42]. Five climatic variables were utilized to represent historical climate (averaging period 1950–2000). These were average minimum monthly temperature (Tmin), average maximum monthly temperature (Tmax), average monthly pre- cipitation (Ptotal) and relative humidity at 09:00 h (RH09:00) and 15:00 h (RH15:00). These variables were also used to typify potential future climate in 2030, 2050, 2070 and 2100. The potential distribution of date palms under future climate was modeled using two Global Climate Models (GCMs), CSIRO- Mk3.0 [42] and MIROC-H (Center for Climate Research, Japan), with the A2 SRES scenario [42–44]. These two GCMs were part of the CliMond dataset and were selected from 23 GCMs based on the following criteria: – All required variables, including temperature, precipitation, sea level pressure and humidity for CLIMEX were available – Small horizontal grid spacing in both GCMs – Better representation of observed climate at local scales, compared to the other GCMs [45]. In the remainder of this paper, MR and CS are used as the abbreviation of MIROC-H and CSIRO-Mk3.0, respectively. The MR model predicts that temperature will increase by approximately 4.31uC, while the CS model predicts a rise of 2.11uC by 2100. There are also differences in rainfall patterns for CS and MR models. For example, the CS model predicts a 14% decrease in future mean annual rainfall, whereas the MR model predicts a 1% decrease [46,47]. The A2 scenario was selected to characterize one of the possible climate scenarios during 2030, 2050, 2070 and 2100. The A2 scenario covers different factors including demographic, economic and technological forces driving GHG emissions; this scenario assumes neither very high nor low global GHG emissions PLOS ONE | www.plosone.org 3 October 2012 | Volume 7 | Issue 10 | e48021