Recent widespread forest expansion and densification in Southwest China

Abstract

Large-scale afforestation and forest conservation policies have been widely implemented in Southwest China over past decades. These efforts have significantly protected the remaining long-established forests in the region and greatly expanded forested areas. Utilizing nearly 30 years of satellite time-series data, we reveal that the region’s enhanced carbon sequestration (3 × 10¹² g·C annually) is primarily driven by crucial changes in forest structure and age, occurring alongside a nearly 120 % increase in forested land area. We observe that dense forests maintain a rapid growth rate of approximately 2.5 % annually for carbon sequestration in the initial years after establishment. However, this growth rate decelerates with increasing apparent forest age. Meanwhile, the densification (modeled as an increasing forest probability) rate of forests reaches its peak growth during the 10–20 year period, sustaining a high annual growth rate of about 1.8 %. We also find that improvements in forest structure, particularly the increasing of forest canopy density and apparent forest age coupled with a notable reduction in forest fragmentation, are also the main driving factors for the enhanced carbon sequestration capacity. Based on these findings, we conclude that forest restoration policies in Southwest China have been successful not only in facilitating large-scale forest growth in Southwest China but, more critically, in promoting the structural maturation (e.g., densification and reduced fragmentation) that is essential for enhancing the region’s carbon sink capacity and its resilience.