Unveiling China's natural and planted forest spatial-temporal dynamics from 1990 to 2020

Understanding the spatial-temporal dynamics of both natural and planted forests is critical for sustainable forest management and assessing ecological benefits or impacts. In 2020, China's forest area encompassed approximately 220 million hectares, accounting for around 5 % of the global forest area. Furthermore, China boasts the largest planted forest area worldwide. However, knowledge regarding the spatial-temporal dynamics of China's natural and planted forests has remained elusive. To fill this gap, we first generated wall-to-wall natural and planted forest maps at 30-m resolution for China every -five years from 1990 to 2020 by using 447,730 images from Landsat-4/5/7/8/9 surface reflectance archive and 656,920 field samples, which were a combination of crowdsourced data and expert knowledge. Secondly, we analyzed the spatial-temporal dynamics of natural and planted forests at multiple -scales from 1990 to 2020. The resultant maps achieved an overall accuracy ranging from 77.33 %+/- 0.67 % to 81.78 % +/- 0.59 % and revealed opposite trends in the areas of natural and planted forests from 1990 to 2020. During these three decades, China's planted forest area increased by 447,500 km2 while the natural forest area decreased by 219,100 km2. The spatial-temporal dynamics of China's natural and planted forests result from China's vast forest management programs in addition to social and economic factors. Variations of these factors at different scales not only determined the primary goals of protecting natural forests and expand planted forests but also resulted in increasing forest areas for many consecutive years by planting forests that offset the loss of natural forests. Our maps provide timely and valuable insights into the benefits and impacts of natural and planted forests in China, which are both closely linked to sustaining human well-being.