Pastures and rangelands underpin global meat and milk production and are a critical resource for millions of people dependent on livestock for food security^1,2. Forage growth, which is highly climate dependent^3,4, is potentially vulnerable to climate change, although precisely where and to what extent remains relatively unexplored. In this study, we assess climate-based threats to global pastures, with a specific focus on changes in within- and between-year precipitation variability (precipitation concentration index (PCI) and coefficient of variation of precipitation (CVP), respectively). Relating global satellite measures of vegetation greenness (such as the Normalized Difference Vegetation Index; NDVI) to key climatic factors reveals that CVP is a significant, yet often overlooked, constraint on vegetation productivity across global pastures. Using independent stocking data, we found that areas with high CVP support lower livestock densities than less-variable regions. Globally, pastures experience about a 25% greater year-to-year precipitation variation (CVP = 0.27) than the average global land surface area (0.21). Over the past century, CVP has generally increased across pasture areas, although both positive (49% of pasture area) and negative (31% of pasture area) trends exist. We identify regions in which livestock grazing is important for local food access and economies, and discuss the potential for pasture intensification in the context of long-term regional trends in precipitation variability.

牧场和牧场是全球肉类和奶类生产的基础，并且是数以百万计依赖牲畜以确保粮食安全的人们的重要资源^1,2。牧草生长高度依赖气候^3,4，尽管气候变化的确切位置和程度尚不明确，但它可能容易受到气候变化的影响。在这项研究中，我们评估了气候对全球牧场的威胁，并特别关注年内和年间降水变化的变化（分别为降水集中指数（PCI）和降水变化系数（CVP））。将全球植被绿色度的卫星测量值（例如归一化差异植被指数； NDVI）与关键气候因素相关联，可以发现CVP是全球牧场上植被生产力的重要但经常被忽视的制约因素。使用独立的库存数据，我们发现CVP较高的地区比可变性较低的地区支持的牲畜密度较低。在全球范围内 牧场的年降水量变化（CVP = 0.27）比全球平均陆地表面积（0.21）大25％。在过去的一个世纪中，尽管牧草面积的正增长趋势（占牧草面积的49％）和消极趋势（占牧草面积的31％）均存在，但牧区的CVP总体上有所增加。我们确定牲畜放牧对当地粮食获取和经济至关重要的区域，并在降水变化的长期区域趋势的背景下讨论牧草集约化的潜力。