What is the main cause of grassland degradation? A case study of grassland ecosystem service in the middle-south Inner Mongolia Zhan Wang a,b,c , Xiangzheng Deng a,c,d, ⁎, Wei Song a , Zhihui Li a,c,d , Jiancheng Chen b a Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China b School of Economics & Management, Beijing Forestry University, Beijing 100083, China c Center for Chinese Agricultural Policy, Chinese Academy of Sciences, Beijing 100101, China d University of Chinese Academy of Sciences, Beijing 10049, China abstract article info Article history: Received 25 December 2015 Received in revised form 22 September 2016 Accepted 11 November 2016 Available online 15 November 2016 In this study, we analyze the changes of indicators of ecosystem services and functions, in order to understand the main cause of grassland degradation due to climatic variation or land use changes in the middle-south Inner Mongolia. The soil nutrient and the water supply of supporting service got recovery during 1988–2008. The loss of net primary production declined, and the quality of the retained unconverted grassland (RUG) even in- creasingly degraded from 2000 to 2008. Analytical results show that environmental degradation on the land- use-changed-area is lower than that on the RUG from 2000 to 2008. It illustrates that climatic variation has more negative impacts on grassland ecosystem service, and which is significantly higher than the so-called “overgrazing” induced grassland degradation. Moreover, it cannot be excluded that those species died out on the RUG due to natural selection or competitive evolution in an evolutionary process under the deteriorative weather condition rather than overgrazing. The positive impacts of human activities such as conservation pro- grams and wildlife protection laws also benefit to regional grassland ecosystem obviously in the study area, so that can delay the environmental degradation even if each planet has its life cycle. It indicates that an integrated regional planning involving the considerations of climatic conditions, geographical characteristics, socioeconom- ic factors, and ecological functions and biodiversity can benefit to regional grassland conservation based on mon- itoring and management via scientific methods. © 2016 Elsevier B.V. All rights reserved. Keywords: Ecosystem assessment Ecosystem service Inner Mongolia Grassland Human wellbeing 1. Introduction Many researchers believe that reclamation, deforestation, and overgrazing in recent decades have induced global desertification and grassland degradation that endanger to regional ecosystem services and functions severely (Gang et al., 2014). Inner Mongolia grassland is the largest pasture in China. It has been a long history to accommodate Mongolian herdsmen over hundreds of years. It includes the large areas of Khorchin, Ulan Qab, Erdos, Hulun Buir, and Xilin Gol. However, Khorchin, Ulan Qab, and Erdos had lost many high quality pastures (Bai et al., 2010). According to Ministry of Environmental Protection of the PR. of China in 1999 survey report, the percentage of total area of the grassland degradation was about to 31.8% of the total grassland area. From 60's to 80's in the 20th century, the total grassland area sharply declined from 88 million ha to 78 million ha, and continually decreasing to 69 million ha until the end of 90's. Khorchin is one of the typical areas suffering from severe degradation. Their people lost their pasture with the rate at 3.7% in every year. Until 2005, Khorchin had lost 50% of high quality grassland. The similar issue occurred in Hulun Buir. Its degradation area expanded from 15 to 49%. In Xilin Gol of Inner Mongolia, degradation occurred over 74% of pasture land. Moreover, grassland degradation has occurred in all the regions of Ongniud Banner, Uxin Banner, Evenk Autonomous Banner, Sonid Left and Right Banners, East Ujimqin Banner, and Wulate Middle Banner of Inner Mongolia. Grassland changes are directly influenced by both climatic variation and human activities (Qi et al., 2012). Many researchers also believe that natural hazards due to climate changes have occurred more fre- quently than before. Inner Mongolia has suffered from droughts for re- cent several decades (Tachiiri et al., 2008; John et al., 2013). Because the annual precipitation is around 100–400 mm, and 70% of them occurred in June throughout August during the summer time; these droughts with strong winds usually happen in spring, so that surface soil is blown away easily. For example, there are severe windy days at 8– 9 grade over 10 days per year at northwest of Xilin Gol, and over 50 days per year at the north of the Yinshan Mountains, over 40 days Catena 150 (2017) 100–107 ⁎ Corresponding author at: Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China. E-mail addresses: wangz@igsnrr.ac.cn (Z. Wang), dengxz.ccap@igsnrr.ac.cn (X. Deng), songw@igsnrr.ac.cn (W. Song), lizh.12b@igsnrr.ac.cn (Z. Li), chenjc1963@163.com (J. Chen). http://dx.doi.org/10.1016/j.catena.2016.11.014 0341-8162/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Catena journal homepage: www.elsevier.com/locate/catena