Satellite Observations of the Recovery of Forests and Grasslands in Western China

Abstract

The Grain for Green Program (GGP), which combats and reverses the landscape-scale habitat degradation by converting agricultural lands to forests and grasslands, was launched in 1999 in western China. An assessment of the extent to which the GGP has altered the vegetation cover and ecological functions in these regions is much needed. The present study initially analyzed land use and cover change of forests and grasslands over western China between 2000 and 2015. A variety of satellite-based ecological indicators, including net primary productivity, normalized difference vegetation index, leaf area index, carbon use efficiency, and water use efficiency, were used to reflect the biophysical consequences of the GGP in western China. Results indicated that the spatial extent of forests and grasslands increased by 13.97 x 10(3) and 11.13 x 10(3) km(2), respectively, which were mainly converted from deserts and croplands. The ecosystem functions of forests and grasslands showed an asymmetric response in northwestern and southwestern China. The normalized difference vegetation index and water use efficiency of forests, as well as the net primary productivity and water use efficiency of grasslands, increased significantly over this period. The GGP also has led to an increase in leaf area index and carbon use efficiency of forests and grasslands. The Loess Plateau and the Three Rivers Source area represent the most effectively recovered regions in western China. Rising precipitation rates have contributed to vegetation recovery to some extent, especially in northwestern China, whereas the GGP was the prominent reason for the improvement of ecosystem functions across the entire region of western China. Plain Language Summary Land degradation has caused severe environmental problems in many areas worldwide and severely restrains the sustainable development of numerous local economies. Land degradation also undermines the livelihoods and food security of people, especially in the economically underprivileged regions. Western China has experienced land degradation because of both its geological location and climatic conditions. To combat and mitigate this situation, the Chinese government implemented a series of national-scale ecological policies and programs during the late 1990s and early 2000s. Nearly 20 years have passed since the implementation of these projects. Therefore, it is appropriate to comprehensively assess the biophysical consequences of these programs. The present study aims to evaluate the extent to which the vegetation of western China recovered during the 2000-2015 period based on a variety of remotely sensed data streams. Results indicated that the spatial extent of forests and grasslands have expanded. The ecosystem functions of forests and grasslands showed an asymmetric response in the southwest and northwest regions of western China. These findings may provide guidelines for government agencies and policy makers involved in initiating adaptation strategies designed to adapt to climate change and to manage vegetation production.