The Hyrcanian Forest region is rich in relict species, and endemic and endangered species. Although there are concerns about climate change, its influence on tree species in the Hyrcanian forests in the north of Iran is still unidentified. Taxus baccata is among the few conifer species found in the region, and the present study aims to evaluate the potential impact of climate change on the distribution of T. baccata. For this purpose, we used ensemble species distribution modeling with ten algorithms and based on two geographic extents (global and regional) and climate data for different climate change scenarios. For the regional extent, we calibrated the models in Hyrcanian forests including the three provinces in the north of Iran. For the global extent, we calibrated the models on the whole range distribution of T. baccata. In both cases, we applied the models to predict the distribution of T. baccata in northern Iran under current, 2050, and 2070 climates. In regional extent modeling, precipitation of coldest quarter and in global extent modeling temperature seasonality emerged as the most important variables. Present environmental suitability estimates indicated that the suitable area for T. baccata in Hyrcanian forests is 5.89 × 103 km2 (regional modeling) to 9.74 × 103 km2 (global modeling). The modeling suggests that climate change under representative concentration pathways (RCP) 8.5 is likely to lead to strong suitability reductions in the region, with just between 0.63 × 103 km2 (regional modeling) and 0.57 × 103 km2 (global modeling) suitable area in 2070. Hence, T. baccata risks losing most currently suitable areas in the Hyrcanian forests under climate change. The results of the present study suggest there should be focus on conservation of areas predicted to remain suitable through near-future climate change and provide an estimate of the availability of suitable areas for the regeneration of T. baccata and its use in reforestation.

中文翻译：

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未来气候对欧洲红豆杉（Taxus baccata L.）在希尔卡尼亚森林地区（伊朗）分布的潜在影响

希尔卡尼亚森林地区拥有丰富的遗存物种、地方性和濒危物种。尽管人们对气候变化感到担忧，但其对伊朗北部希尔卡尼亚森林中树种的影响仍不明朗。Taxus baccata 是该地区发现的少数针叶树种之一，本研究旨在评估气候变化对 T. baccata 分布的潜在影响。为此，我们使用具有十种算法的集合物种分布建模，并基于两个地理范围（全球和区域）和不同气候变化情景的气候数据。对于区域范围，我们校准了包括伊朗北部三个省在内的希尔卡尼亚森林中的模型。在全球范围内，我们校准了 T. baccata 整个范围分布的模型。在这两种情况下，我们应用这些模型来预测伊朗北部在当前、2050 年和 2070 年气候下 T. baccata 的分布。在区域范围建模中，最冷季降水和全球范围建模温度季节性成为最重要的变量。目前的环境适宜性估计表明，Hyrcanian 森林中 T. baccata 的适宜面积为 5.89 × 103 平方公里（区域模拟）至 9.74 × 103 平方公里（全球模拟）。该模型表明，代表性浓度路径 (RCP) 8.5 下的气候变化可能会导致该地区的适宜性大幅降低，2070 年适宜面积仅介于 0.63 × 103 平方公里（区域模拟）和 0.57 × 103 平方公里（全球模拟）之间. 因此，在气候变化下，T. baccata 有可能失去目前希尔卡尼亚森林中最适合的地区。