Grazing by domestic herbivores is the most widespread land use on the planet, and also a major global change driver in grasslands. Yet, experimental evidence on the long-term impacts of livestock grazing on biodiversity and function is largely lacking. Here, we report results from a network of 10 experimental sites from paired grazed and ungrazed grasslands across an aridity gradient, including some of the largest remaining native grasslands on the planet. We show that aridity partly explains the responses of biodiversity and multifunctionality to long-term livestock grazing. Grazing greatly reduced biodiversity and multifunctionality in steppes with higher aridity, while had no effects in steppes with relatively lower aridity. Moreover, we found that long-term grazing further changed the capacity of above- and below-ground biodiversity to explain multifunctionality. Thus, while plant diversity was positively correlated with multifunctionality across grasslands with excluded livestock, soil biodiversity was positively correlated with multifunctionality across grazed grasslands. Together, our cross-site experiment reveals that the impacts of long-term grazing on biodiversity and function depend on aridity levels, with the more arid sites experiencing more negative impacts on biodiversity and ecosystem multifunctionality. We also highlight the fundamental importance of conserving soil biodiversity for protecting multifunctionality in widespread grazed grasslands.

家养食草动物的放牧是地球上最广泛的土地利用方式，也是全球草原变化的主要驱动力。然而，关于牲畜放牧对生物多样性和功能的长期影响的实验证据却很缺乏。在这里，我们报告了由 10 个实验地点组成的网络的结果，这些实验地点来自干旱梯度上配对的放牧和未放牧草原，其中包括地球上现存的一些最大的原生草原。我们表明，干旱在一定程度上解释了生物多样性和多功能性对长期牲畜放牧的反应。放牧在干旱度较高的草原上大大降低了生物多样性和多功能性，而在干旱度相对较低的草原上则没有影响。此外，我们发现长期放牧进一步改变了地上和地下生物多样性解释多功能性的能力。因此，虽然植物多样性与排除牲畜的草地的多功能性呈正相关，但土壤生物多样性与放牧草地的多功能性正相关。总之，我们的跨地点实验表明，长期放牧对生物多样性和功能的影响取决于干旱程度，越干旱的地区对生物多样性和生态系统多功能性的负面影响越大。我们还强调保护土壤生物多样性对于保护广泛放牧草地的多功能性的根本重要性。