Impact of Human Activities and Climate Change on Grassland Productivity in Xilingol League

Natural grasslands are increasingly subjected to the dual stresses of grazing pressures and climate change. However, the contribution of human activities, especially grassland ecology conservation projects, to grassland improvement remains ambiguous. Utilizing MODIS satellite data in conjunction with the VPM model, the gross primary productivity (GPP) changes in the Xilingol grassland from 2000 to 2020 were assessed. Based on GPP data derived from remote sensing, this study quantitatively assessed the spatiotemporal dynamics of the impacts of climate change and human activities on the productivity of grassland in the Xilingol League. From 2000 to 2020, the grasslands exhibited a greening trend characterized by a significant annual GPP increment of 2.66 gC m–2 yr–1 (P<0.05). Climate change and human activities jointly contributed to this greening trend, with relative contribution rates of 55% and 45%, respectively. However, the relative contributions of climate change and human activities to the trend of GPP varied greatly in different regions. Climate change emerged as the principal driver in the central and eastern regions of Xilingol League with robust grass growth, accounting for more than 65% of the GPP enhancement. Conversely, human activities were the dominant factors in less verdant western regions and the agro-pastoral ecotone, representing more than 60% of the GPP change. Grassland productivity was sensitive to grassland ecological restoration measures, with significant changes in the trends of grassland productivity attributed to human activities in pivotal policy implementation years such as 2005 and 2011. Specifically, measures such as the control of wind/sand sources and returning grazing land to grassland from 2000 to 2005 gradually alleviated the pressure of human activities on grassland productivity, as they significantly improved vegetation growth in high-quality grasslands. Under the forage-livestock balance policy from 2005 to 2011, inadequate compensation for grassland ecological protection led to a significant reduction in GPP, as some herders increased their livestock holdings despite grazing restrictions, and this particularly affected the high-quality grasslands. The implementation of the Grassland Ecological Protection Subsidy and Reward Program from 2011 to 2020 generally promoted the recovery of productivity in eastern and western Xilingol League grasslands, but significant ecological pressure persisted. This study provides theoretical support for optimizing grassland ecosystem management and forming a virtuous cycle of grassland conservation in pastoral areas.