This study focuses on heat stress conditions for dairy cattle production in West Africa under current and future climatic conditions. After testing the accuracy of the dynamically downscaled climate datasets for simulating the historical daily maximum temperature (Tmax) and relative humidity (RH) in West Africa for 50 meteorological stations, we used the dataset for calculating the temperature-humidity index (THI), i.e., an index indicating heat stress for dairy cattle on a daily scale. Calculations were made for the historical period (1981–2010) using the ERA-Interim reanalysis dataset, and for two future periods (2021–2050 and 2071–2100) using climate predictions of the GFDL-ESM2M, HadGEM2-ES, and MPI-ESM-MR Global Circulation Models (GCMs) under the RCP4.5 emission scenario. Here, we show that during the period from 1981 to 2010 for > 1/5 of the region of West Africa, the frequency of severe/danger heat events per year, i.e., events that result in significant decreases in productive and reproductive performances, increased from 11 to 29–38 days (significant at 95% confidence level). Most obvious changes were observed for the eastern and southeastern parts. Under future climate conditions periods with severe/danger heat stress events will increase further as compared with the historical period by 5–22% depending on the GCM used. Moreover, the average length of periods with severe/danger heat stress is expected to increase from ~ 3 days in the historical period to ~ 4–7 days by 2021–2050 and even to up to 10 days by 2071–2100. Based on the average results of three GCMs, by 2071–2100, around 22% of dairy cattle population currently living in this area is expected to experience around 70 days more of severe/danger heat stress (compare with the historical period), especially in the southern half of West Africa. The result is alarming, as it shows that dairy production systems in West Africa are jeopardized at large scale by climate change and that depending on the GCM used, milk production might decrease by 200–400 kg/year by 2071–2100 in around 1, 7, or 11%. Our study calls for the development of improved dairy cattle production systems with higher adaptive capacity in order to deal with expected future heat stress conditions.

中文翻译：

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未来西非奶牛生产是否会面临热应激的挑战？

本研究侧重于当前和未来气候条件下西非奶牛生产的热应激条件。在测试了用于模拟西非 50 个气象站的历史日最高温度 (Tmax) 和相对湿度 (RH) 的动态缩减气候数据集的准确性后，我们使用该数据集计算了温湿度指数 (THI)，即，一个指示奶牛每天热应激的指数。使用 ERA-Interim 再分析数据集对历史时期（1981-2010）进行了计算，并使用 GFDL-ESM2M、HadGEM2-ES 和 MPI-的气候预测对未来两个时期（2021-2050 和 2071-2100）进行了计算。 RCP4.5 排放情景下的 ESM-MR 全球环流模型 (GCM)。在这里，我们表明，在 1981 年至 2010 年期间，对于 > 西非地区的 1/5，每年严重/危险高温事件的频率，即导致生产和繁殖性能显着下降的事件，从 11 天增加到 29-38 天（在 95% 置信水平上显着） ）。在东部和东南部观察到最明显的变化。在未来的气候条件下，根据所使用的 GCM，与历史时期相比，发生严重/危险热应激事件的时期将进一步增加 5-22%。此外，预计严重/危险热应激的平均时间长度将从历史时期的约 3 天增加到 2021-2050 年的约 4-7 天，甚至到 2071-2100 年增加到 10 天。根据三个 GCM 的平均结果，到 2071-2100 年，目前生活在该地区的约 22% 的奶牛种群预计将经历约 70 天左右的严重/危险热应激（与历史时期相比），尤其是在西非南半部。结果令人震惊，因为它表明西非的乳制品生产系统受到气候变化的大规模危害，并且根据所使用的 GCM，到 2071-2100 年，牛奶产量可能会减少 200-400 公斤/年，大约 1, 7 或 11%。我们的研究呼吁开发具有更高适应能力的改良奶牛生产系统，以应对预期的未来热应激条件。因为它表明西非的乳制品生产系统受到气候变化的大规模危害，并且根据所使用的 GCM，到 2071-2100 年，牛奶产量可能会减少 200-400 公斤/年，下降幅度约为 1%、7% 或 11% . 我们的研究呼吁开发具有更高适应能力的改良奶牛生产系统，以应对预期的未来热应激条件。因为它表明西非的乳制品生产系统受到气候变化的大规模危害，并且根据所使用的 GCM，到 2071-2100 年，牛奶产量可能会减少 200-400 公斤/年，下降幅度约为 1%、7% 或 11% . 我们的研究呼吁开发具有更高适应能力的改良奶牛生产系统，以应对预期的未来热应激条件。