Evaluating the effect of ecological policies from the pattern change of persistent green patches–A case study of Yan'an in China's Loess Plateau

Abstract

Evaluation from landscape pattern change can comprehensively reflect the impact of ecological policies on the ecosystem service function. However, previous assessments based on landscape patterns only considered land cover type and ignored the quality of vegetation cover, which could hardly reflect regional differences in restoration durability and sustainability. Based on the temporal phase characteristics of the vegetation index, this study proposes the concept of Persistent Green Patches (PGPs). Taking Yan'an, a key area for the implementation of ecological projects in the Loess Plateau, as a study area, the effect of ecological policies was evaluated from the pattern change of PGPs from 2000 to 2017 through Morphological Spatial Pattern Analysis (MSPA). It is found that (1) the area of PGPs was increased from 14.45% to 44.26% in Yan'an since the implementation of the ecological projects; (2) the Grain for Green projects can hardly form a short-term increase of PGPs; while the Natural Forest Protection projects can quickly increase the PGPs area, its effect would tend to be saturated or even decrease in the long term; (3) the fragmentation and connectivity of the landscape show that the ecological projects promote the connection between different green patches, and improves the overall connectivity of the PGPs. This study provides a new perspective on evaluating the effect of ecological projects, which is expected to provide a reference for the future optimization of relevant ecological policies and regional sustainable development.