NDVI-derived forest area change and its driving factors in China

China harbors diversified forest types, from tropical rainforest to boreal coniferous forest, and has implemented large-scale reforestation/afforestation programs over the past several decades. However, little information is available on changes in China’s forest area and the causes. In this study, we used the classified forest distribution thematic map derived from Normalized Difference Vegetation Index (NDVI) datasets and a revised IPAT model to examine China’s forest area change and the possible driving factors from 1982 to 2006. Overall, NDVI-derived forest areas were numerically consistent with those reported in the 3rd, 4th, 5th, and 6th National Forest Inventories, respectively. Over the past 25 years, China’s forest area was estimated to have an average of 169.18 million hectares with an annual increase of 0.15 million hectares (c.a. a total net increment of 3.60 million hectares), which is equivalent to 0.089% of the relative annual change rate. However, a large difference in the changing rate and direction of forest area at the province level was found; for instance, forest area has declined in 10 provinces, mainly in Northeastern and Southern China, while 21 provinces showed an increase. The changes were most likely attributed to the policy regarding the import and export of timber and affluence (per capita gross domestic product), and both contributed more than 80% of the total contribution of the six factors of the revised IPAT model.

中国拥有涵盖热带雨林至北方针叶林的多样森林类型，并在过去数十年间实施了大规模的造林与再造林工程。然而，当前关于中国森林面积变化及其成因的相关信息仍较为匮乏。本研究借助基于归一化差分植被指数（Normalized Difference Vegetation Index, NDVI）数据集生成的分类森林分布专题图，以及修正后的IPAT模型，探究了1982至2006年间中国森林面积的变化情况及其潜在驱动因子。总体而言，通过NDVI反演得到的森林面积数值，分别与第三、四、五、六次全国森林资源清查结果基本一致。在过去25年间，中国森林面积的年均值约为1.6918亿公顷，年均增长0.15百万公顷（总净增量约3.60百万公顷），相对年变化率为0.089%。但省级尺度上的森林面积变化速率与方向存在显著差异：例如，中国东北与华南地区的10个省份森林面积出现下降，而21个省份的森林面积呈增长态势。上述变化主要归因于木材进出口政策与人均富裕程度（人均国内生产总值）两类驱动因子，二者在修正后IPAT模型的六大影响因子总贡献占比中超过80%。