Cedrus distribution change: past, present, and future

Cedrus Trew (Pinaceae) includes four species, which are disjunctively distributed in the Mediterranean region and western Himalaya. Understanding the historical distribution of Cedrus and the driving factors can provide valuable information for the conservation of these species. In this study, we collected current distribution data and pollen fossil records for Cedrus. We used MaxEnt to simulate the distribution of Cedrus in the Mediterranean region and western Himalaya during the Last Glacial Maximum (LGM), the middle Holocene (MH), present and future in response to different climate scenarios. Our simulation results indicate that winter precipitation is the key factor that determines the distribution of Cedrus, followed by winter temperature. The results also show that summer precipitation had a more important impact in the Mediterranean region than in the western Himalaya. The results indicate that climate change exerts a significant impact on the distribution of Cedrus in the Mediterranean, but not as much as in the western Himalaya. This could be attributed to the greater availability of microclimates (climate niche space) in the latter region. The availability of microclimates associated with the complex topography in the western Himalaya. The simulated results are generally consistent with fossil data. In the Mediterranean region, the suitability of the habitats for Cedrus decreased continuously from the LGM to the year 2070, with a distinct drop from the LGM to the MH. In the western Himalaya, the potential suitability of habitats for Cedrus increased from the LGM to the MH, but might fluctuate in the future. In general, this study identifies the key climate factors restricting the natural distribution of Cedrus. It shows that the distribution of Cedrus would be reduced in response to global climate change in the future, which indicates an urgent need for the protection and management of Cedrus populations.