4. Impact Assessments of Land-Use Change and Climate Change on Ecosystem Services of Grassland

The grassland is an important land-use type that plays an important role in the ecosystem service supply in China. It is of great significance to the grassland management to determine the changing trend of grassland productivity and its response to land-use change and climate change. In this chapter, we first examined changes in grassland productivity due to climate and land-use change in the Three-River Headwaters region (TRHR) of Qinghai Province. In the macrocontext of climatic change, we analyzed the possible changing trends of the net primary productivity (NPP) of local grasslands under four representative concentration pathways (RCPs) scenarios (i.e., RCP2.6, RCP4.5, RCP6.0, and RCP8.5) during 2010–2030 with the model estimation, and the grass yield and theoretical grazing capacity under each scenario were further qualitatively and quantitatively analyzed. The results indicate that the grassland productivity in the TRHR will be unstable under all the four scenarios. The grassland productivity will be greatly influenced by the fluctuations of precipitation, and the temperature fluctuations will also play an important role during some periods. The local grassland productivity will decrease to some degree during 2010–2020 and then will fluctuate and increase slowly during 2020–2030. The theoretical grazing capacity was analyzed in this study and calculated on the basis of the grass yield. The result indicates that the theoretical grazing capacity ranges from 4 to 5 million sheep under the four scenarios and it can provide quantitative information reference for decision making on how to determine the reasonable grazing capacity, promote the sustainable development of grasslands, and so forth. Further, we estimated changes in economic returns of livestock production in the TRHR of China. The land surface in TRHR, a typical ecological fragile zone of China, is quite sensitive to the climate change which will destabilize certain ecosystem service valuable to the entire nation and neighboring countries. We analyzed the impacts of climate change and agents’ adaptive behaviors on the regional land-use change with the agent-based model (ABM). First, the main agents were extracted according to the production resource endowments and socioeconomic background. Then, the agents’ land-use behaviors were analyzed and parameterized. Thereafter, the ABM model was built to simulate the impacts of climate change on the regional land-use change and agents’ economic benefits. The results showed that the land-use change was mainly characterized by the increase of grassland and decrease of unused land area. Besides, the agents would get more wealth under the scenario without climate change in the long term, even though the total income is lower than that under the scenario with climate change. In addition, the sensitivity analysis indicated that the model is sensitive to the climatic conditions, market price of agricultural and animal husbandry products, government subsidies, and cost control. Finally, we predicted changes in grassland productivity in China. The results showed that, firstly, the relationship between grassland productivity and climate change, geographical conditions, and human activities was analyzed with the panel data of the whole China during 1980–2010. The result indicated that the temperature and precipitation were very important to grassland productivity at the national scale; secondly, the grassland in China was divided into seven grassland ecological–economic zones according to the ecosystem service function and climate characteristics. The relationship between grassland productivity and climate change was further analyzed at the regional scale. The result indicated that the temperature is more beneficial to the increase of the grassland productivity in the Qinghai–Tibet Plateau and the Southwest Karst shrubland region; thirdly, the increase of the temperature and precipitation can increase the grassland productivity and consequently relieve the pressure according to the climate factors of simulation with the community climate system model v4.0 (CCSM). However, the simulation result indicates that the human pressure on grasslands is still severe under the four RCPs scenarios and the grassland area would reduce sharply due to the conversion from the grassland to the cultivated land. What is more, there is still a great challenge to the increase of total grassland productivity in China.