Driving forces of grass-livestock balance shifted from human activities to climate change on the top of the earth

Abstract

Climate change and intensive grazing are threatening key functions of grassland ecosystems, including biodiversity, soil retention, and supporting pastoralist livelihoods. However, where and to what extent these factors impact grassland ecological balance on the top of the earth remained unclear. This study focused on the alpine grassland ecosystems in and around the Mount Qomolangma National Nature Reserve (MQNNR), coupled with remote sensing and socio-economic data to evaluate the state of grass-livestock balance during 2000–2019, and revealed the actual contributions of climate, soil attributes, and human activities to the grassland carrying capacity (GCC) changes by employing ridge regression and structural equation modeling. The results showed that the multiyear mean grass-livestock pressure index (GLPI) for the study area was 0.62, indicating that the grasslands generally provided sufficient forage for livestock. However, 21.5 % of the area remained at risk of overgrazing, predominantly in valley regions with high human activity. During 2000–2019, approximately 42.3 % of the region experienced a significant increase in GCC, notably in Ngamring, Tingri, and Dinggye. Post-2007, the makeable improvement in GCC was accompanied by a gradual decline in the actual stocking rate, which further alleviated grazing pressure. Furthermore, climate change, soil conditions, and population pressure were the primary drivers of GCC changes, and their contributions to GCC rise/declined area differed significantly across time. Over time, the dominant factors influencing GCC change trend in more than 85 % of the study regions have shifted from human activities to climatic factors, especially the positive contribution from better moisture conditions. This study provides new insights for grassland management and sustainable development, aiding in addressing grassland ecological problems and safeguarding the well-being of pastoral communities and ecological security.