Ecosystem service, threat and conservation
The grassland ecosystems have been traditionally used as grazing lands (rangelands), supporting nomadic herders for animal production by providing fiber, food for livestock and dung as the main source of fuel. Other ecosystem services include regulating services such as prevention of wind erosion and sand fixation, climate regulation; supporting services such as primary production, conservation of water and soil resources, carbon sequestration and biodiversity conservation; as well as cultural services such as ecotourism. Pastures on Tibetan Plateau are particularly important in a national and even international perspective as the form the main land cover around the headwaters of southern Asia’s major rivers.
Main threats for those grasslands are similar as in most other grassland systems over the world, i.e. climate change and overgrazing, while conversion to crop land has been less common than in steppes of Western and Central Eurasia. The semi-arid region in China was the region where the greatest climate warming trend was observed in China, with the climate becoming warmer and drier with at an accelerating rate. Significant warming and large and potentially even increasing inter-annual variation in precipitation have started to constrain growth of temperate and alpine steppe grasslands, and also affect livelihoods of pastoralists in natural grassland regions. On the Qinghai-Tibetan Plateau, warming increased net primary production and soil respiration, and lead to significant permafrost thawing and glacier melting, which result in substantially increased methane consumption of meadows. Increased precipitation levels were shown to be favorable for alpine meadow due to the increased aboveground biomass.
Management measures to adapt to climate variability and changes in the steppe region include selling livestock, buying fodder, reserving pastures for extreme climate events, housing livestock in stables and looking for other alternative jobs to compensate for economic losses. Local ecological knowledge and community-based institutions are beneficial to improve resource availability and distribution, and to reduce risks caused by climate change.
Over-grazing has been considered as one of the main cause for grassland degradation. However, effects of grazing on communities are strongly mediated by vegetation type and the given climatic context. Large-scale grazing enclosure experiments from Inner Mongolia suggested that grazing reduces community cover, height, species richness, and aboveground biomass in meadows and typical steppes, but not in desert steppes. Vegetation type explains the largest share of the variations in those variables. A summary of a larger number of case studies across Chinese grasslands suggests that locally increased grazing intensity indeed has negative effects on vegetation cover and aboveground biomass, but does not necessarily reduce plant species richness, while effects on soil conditions vary also among grassland types and are site-dependent. In semi-humid alpine meadows, grazing effects on vegetation are more obvious than in semi-arid steppes. These results suggest that managing stocking rates is important in relatively stable alpine meadow systems, while developing management regimes adaptive to the highly variable environment is more important in the steppes. The latter represent examples of non-equilibrium systems in terms of rangeland ecology, where common droughts result in frequent collapses of livestock herds that never reach stable levels.
Grazing has significantly changed plant communities and soil fertility in areas close to herders’ camps across Tibetan grasslands due to the combined effects of mechanical disturbance and heavy nutrient input from livestock. Given the current trend toward reduced mobility of local herders as a consequence of national sedentarization policies, size of these areas could increase, leading to more widespread degradation.
As China advances in environmental conservation, ecology-related laws and regulations have been improved. As an example of important steps taken by the state to protect the environment, the so-called ecological compensation mechanism is becoming widely applied across the Qinghai-Tibet Plateau region. China has initiated a series of ecological compensation mechanisms, including transfer payments for key ecological function zones, forest ecological benefit compensation, grassland ecological protection subsidies and rewards, and wetland ecological benefit compensation. In 2008-2017, the central government made transfer payments of RMB 16.29 billion and RMB 8.35 billion to the key ecological function zones in Qinghai and Tibet, covering 77 key counties and all areas prohibited to development by the state (China SCIO, 2018). Since “green for grass” project (“tui mu huan cao”) started in 2003, central government has invested RMB 255.7 billion until 2016 according to Annual monitoring report of grasslands in 2013.
According to the recent update at end of 2017, there are four Nature reserves of grassland and meadow at national level, and 12 at provincial level, comprising in total ca. 1.65 million km² (165 million ha). The first and largest (about 123, 100 km2) of the 10 pilot national parks in China is located in Qinghai province, encompassing the headwaters of three major rivers. Community engagement and participation in developing localized schemes for natural resource utilization and conservation are given special attention in the ongoing programs for environmental conservation in China. The most prominent examples include:
- Chen, H., Zhu Q.A., Peng C.H., et al.(2013). The impacts of climate change and human activities on biogeochemical cycles on the Qinghai-Tibetan Plateau. Global Change Biology 19, 2940–2955.
- China SCIO (The State Council Information Office of the People’s Republic of China (2018). Ecological Progress on the Qinghai-Tibet Plateau http://subsites.chinadaily.com.cn/ministries/scio/2018-07/31/c2592082.htm
- Foggin, M. (2018). Environmental Conservation in the Tibetan Plateau Region: Lessons for China’s Belt and Road Initiative in the Mountains of Central Asia. Land. 7. 52. 10.3390/land7020052.
- Fu, G., Shen, Z.X. and Zhang, X.Z. (2018). Increased precipitation has stronger effects on plant production of an alpine meadow than does experimental warming in the Northern Tibetan Plateau. Agricultural and Forest Meteorology 249, 11–21.
- Fu, Y., Grumbine, R.E., Wilkes, A., et al. (2012). Climate change adaptation among Tibetan pastoralists: challenges in enhancing local adaptation through policy support. Environmental Management 50, 607–621.
- Grasslands and Grassland Sciences in Northern China (1992) Committee on Scholarly Communication with the People’s Republic of China (U.S.). (1992). Grasslands and grassland sciences in northern China: A report of the Committee on Scholarly Communication with the People’s Republic of China, Office of International Affairs, National Research Council. Washington, D.C: National Academy Press. https://www.nap.edu/read/1942/chapter/6
- Hou, X.Y., Han, Y. and Li, F.Y. (2012). The perception and adaptation of herdsmen to climate change and climate variability in the desert steppe region of northern China. The Rangeland Journal 34, 349-357.
- State Environmental Protection Administration (2017). Report on the state of environment in China. Bejing: Ministry of Ecology and Environment. (in Chinese)
- Su, R., Cheng, J., Chen, D. et al. (2017) Effects of grazing on spatiotemporal variations in community structure and ecosystem function on the grasslands of Inner Mongolia, China. Scientific Report 7, 40, doi: 10.1038/s41598-017-00105-y. https://www.nature.com/articles/s41598-017-00105-y
- Wang, Y., Wesche, K. Vegetation and soil responses to livestock grazing in Central Asian grasslands: a review of Chinese literature. Biodiversity and Conservation (2016) 25: 2401. https://doi.org/10.1007/s10531-015-1034-1 https://link.springer.com/article/10.1007/s10531-015-1034-1
- Wang, Y., Heberling, G., Görzen, E., et al. (2017). Combined effects of livestock grazing and abiotic environment on vegetation and soils of grasslands across Tibet. Applied Vegetation Science 20, 327–339.
- Wang, Y., Lehnert, L.W., Holzapfel, M., et al. (2018). Multiple indicators yield diverging results on grazing degradation and climate controls across Tibetan pastures. Ecological Indicators 93, 1199–1208.