Vegetation Greenness Changes in Northeast China Dominated by Climate Change and Ecological Restoration

Vegetation in Northeast China has undergone complex changes under the dual pressures of climate change and human activities. Quantifying long-term vegetation dynamics and identifying their key drivers are critical for regional sustainability, ecological engineering construction, and environmental conservation. Ecological restoration plays a pivotal role in vegetation protection and recovery in this region; however, it has often been overlooked as a core driver in previous studies. This study analyzed the spatiotemporal dynamics of vegetation in Northeast China based on the long-term satellite-based leaf area index (LAI) datasets from 2000 to 2020, investigated the factors driving the spatiotemporal variation in LAI, and quantified the respective contributions of climate change and human activities to its change. The results showed that: (1) The LAI in Northeast China increased at a rate of 0.0292 yr−1 since 2000, with 80.8% of the region showing vegetation improvement, predominantly within ecological restoration zones; however, urbanization induced severe local vegetation degradation. The Natural Forest Conservation Program (NFCP) exhibited the highest LAI growth rate (0.0315 yr−1), followed by the Shelterbelt Program for Liaohe River (SPLR) and the Three-North Shelterbelt Program (TNSP) (0.0313 yr−1 and 0.0294 yr−1, respectively). (2) Land use type, soil type, and evapotranspiration were the primary single drivers of LAI spatial heterogeneity, and the interaction between land use and soil types has the most significant impact on it. (3) Climate change and human activities jointly accounted for 78.4% of the LAI variations across the study area, with the relative contribution of human activities (CHA = 68.9%) being significantly higher than that of climate change (CCC = 31.1%). In the vegetation browning regions of the three ecological restoration zones, the contribution of human activities exceeded 60%. In contrast, the dominant drivers of vegetation greening varied substantially among the zones: greening in the TNSP and SPLR was primarily regulated by climate change (CCC > 50%), whereas in the NFCP it was mainly driven by human activities. This study highlights the key role of human activities (especially ecological restoration programs) in the improvement of vegetation cover in Northeast China, which can help to assess the benefits of ecological restoration in Northeast China, provide references for ecological and environmental management policy formulation, and promote the construction of regional ecological civilization.