Chen Chi, Park Taejin, Wang Xuhui, Piao Shilong, Xu Baodong, Chaturvedi Rajiv K, Fuchs Richard, Brovkin Victor, Ciais Philippe, Fensholt Rasmus, Tømmervik Hans, Bala Govindasamy, Zhu Zaichun, Nemani Ramakrishna R, Myneni Ranga B
Department of Earth and Environment, Boston University, Boston, MA 02215, USA.
Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.
Nat Sustain. 2019;2:122-129. doi: 10.1038/s41893-019-0220-7. Epub 2019 Feb 11.
Satellite data show increasing leaf area of vegetation due to direct (human land-use management) and indirect factors (climate change, CO fertilization, nitrogen deposition, recovery from natural disturbances, etc.). Among these, climate change and CO fertilization effect seem to be the dominant drivers. However, recent satellite data (2000-2017) reveal a greening pattern that is strikingly prominent in China and India, and overlapping with croplands world-wide. China alone accounts for 25% of the global net increase in leaf area with only 6.6% of global vegetated area. The greening in China is from forests (42%) and croplands (32%), but in India is mostly from croplands (82%) with minor contribution from forests (4.4%). China is engineering ambitious programs to conserve and expand forests with the goal of mitigating land degradation, air pollution and climate change. Food production in China and India has increased by over 35% since 2000 mostly due to increasing harvested area through multiple cropping facilitated by fertilizer use and surface/ground-water irrigation. Our results indicate that the direct factor is a key driver of the "Greening Earth", accounting for over a third, and likely more, of the observed net increase in green leaf area. They highlight the need for realistic representation of human land-use practices in Earth system models.
卫星数据显示，由于直接因素（人类土地利用管理）和间接因素（气候变化、二氧化碳施肥、氮沉降、从自然干扰中恢复等），植被叶面积在增加。其中，气候变化和二氧化碳施肥效应似乎是主要驱动因素。然而，最近的卫星数据（2000 - 2017年）揭示了一种绿化模式，这种模式在中国和印度尤为显著，并与全球农田重叠。仅中国就占全球叶面积净增加量的25%，而其植被面积仅占全球的6.6%。中国的绿化来自森林（42%）和农田（32%），但印度的绿化主要来自农田（82%），森林贡献较小（4.4%）。中国正在实施雄心勃勃的森林保护和扩张计划，目标是减轻土地退化、空气污染和气候变化。自2000年以来，中国和印度的粮食产量增长超过35%，这主要归功于通过使用化肥和地表水/地下水灌溉实现多季种植从而增加了收获面积。我们的研究结果表明，直接因素是“地球绿化”的关键驱动因素，占观测到的绿叶面积净增加量的三分之一以上，甚至可能更多。这些结果凸显了在地球系统模型中切实体现人类土地利用实践的必要性。
