Changes in habitat quality of nature reserves in depopulating areas due to anthropogenic pressure: Evidence from Northeast China, 2000-2018

The increasing human impact on the global environment has led to biodiversity decline and species extinction. The establishment of nature reserves is recognized as the most effective way to minimize human disruption and curb continuing threats to the Earth's life support system. Many areas in the world are currently witnessing depopulation trends. How does anthropogenic pressure change within nature reserves in these areas? How will this change affect the quality of their habitats? As a typical depopulating area and a main distribution area of China's nature reserves, Northeast China is an ideal region for exploring these scientific issues. In this research, we mapped anthropogenic pressure and habitat quality within 93 nature reserves in Northeast China from 2000 to 2018 and explored their correlation. We found that in Northeast China-a typical depopulating area-the anthropogenic pressure within nature reserves has been greatly eased and the habitat quality has improved. Along with depopulation, the anthropogenic pressure in more than half of the protected area in Northeast China declined between 2000 and 2018. Net primary production increased in almost all nature reserves, and fractional vegetation cover improved in three quarters of nature reserves. However, the vegetation aggregation index showed a downward trend. The overall performance of the national nature reserves surpasses that of the local nature reserves. Pearson's correlation coefficient showed a statistically significant negative correlation between habitat quality indices and anthropogenic pressure categories. The highest negative correlation was observed between the vegetation aggregation index and land use intensity. Based on the propensity score matching approach, we classified nature reserves in Northeast China according to their conservation effectiveness relative to matched unprotected control sites. Finally, recommendations such as transferring governmental protection investment, broadening funding sources, and joining in international evaluation networks are proposed.