| Paddy field is one of the most important agricultural ecosystems in China. Besides providing food and raw materials, paddy fields also have many important ecosystem service functions, such as cooling temperature in summer, CO2 sequestration, and flood mitigation. With the increasing deterioration of environment and shortage of water resource, the ecosystem service function of paddy field played more important role in the sustainable development of the human society. An integrated evaluation on the ecosystem service value (ESV) of paddy field is significant for the development of rice production in China. Previous studies mostly focused on the evaluation of the current situation of regional ESV. The historical change, influencing factors and compensation mechanism of ESV have not been well documented. Therefore, in this study, we analyzed the change of total amount, structure and density of ESV during 1980-2014 based on the data of rice production, meteorology, investigation and field monitoring. Furthermore, we investigated the impacts of the development of rice cultivation technology, climate change and spatial distribution change on the ESV of paddy field during the last three decades. Additionally, we conducted an empirical research to study the ecological compensation mechanism for paddy field. These results would provide good references for the protection of paddy field and for the sustainable development of rice production in China. The primary results of this study were listed below:(1) A great spatial-temporal variation was existed in the total amount, structure and density of ESV of paddy field during 1980-2014. The total ESV of paddy field presented an increased trend during last three decades. The total amount of ESV in 2014 reached to 2371.25 billion yuan, which was 36.5% higher than that in 1980. The percentage of CO2 sequestration was the highest in six ecosystem service functions, and followed by regulating temperature and greenhouse gas (GHG) emission. The percentage of flood mitigation and GHG reduced during last three decades. The area-and yield-scaled ESV were 7.96-11.18yuan/m2 and 11.21-13.63 yuan/kg, respectively. The area-scaled ESV significantly increased during 1980-2014, while the yield-scaled ESV did not present an obvious increasing trend. The total amount, structure and density of ESV showed great spatial variation in different rice planting regions.(2) The development of rice cultivation technology showed an obvious impact on the ESV of paddy field. The development of rice nurseries decreased the ESV of GHG emission by 5.579 billion yuan. The reduction of the ESV of Zone I to IV was 0.73,1.363,1.19 and 2.367 billion yuan, respectively. The development of irrigation reduced the ESV of GHG emission by 305.12 billion yuan. However, the development of rice transplanting method raised the ESV of GHG emission by 2.06 billion yuan. Increased application of N fertilizer raised the ESV of CO2 sequestration (88.09 billion yuan), O2 production (27.48 billion yuan), chemical pollution (15.76 billion yuan), and GHG emission (47.11 billion yuan). The application of N fertilizer raised more positive ESV than negative ESV.(3) Climate change increased the ESV of temperature cooling, while reduced the ESV flood mitigation in the last three decades. The ESV of temperature cooling presented an increasing trend by the influencing of net radiation, temperature, and wind speed since 1980. The ESV of temperature cooling was enhanced by 13.8%, 45.8% and 83.9% for early, middle and late rice, respectively. However, the ESV of flood mitigation was reduced by 91.5%,89.1% and 81.5% for early, middle and late rice, respectively. The impacts of climate change on the ESV of these two functions showed great spatial variation. The ESV of temperature cooling for Zone I fluctuated during last three decades. While for other three zones, the ESV of temperature cooling was increased by 96.8%(Zone Ⅱ),88.2%(Zone Ⅲ) and 39.0% (Zone IV), respectively. The ESV of flood mitigation was reduced 16.5%,12.5%,12.5%, and 12.0% for Zone I to IV, respectively. Net radiation, Tmean, Tmax and Tmin showed positive correlation with the ESV of temperature cooling, while relative humid showed negative correlation. The correlation of ESV with metrological factors was different among four rice planting zones.(4) North migration of rice production reduced the total amount and density of the ESV of paddy field in China. Its impacts showed great spatial variation. North migration decreased the total ESV of paddy field by 15.8%. The ESV of six functions was reduced by 13.1-27.7% under north migration scenario. North migration significantly mitigated the area-scaled ESV by 14.2%; but its effect on yield-scaled ESV was not significant. The total ESV for Zone Ⅱ,Ⅲ and Ⅳ was reduced under north migration scenario. The area-scaled ESV of 12 provinces in Zone Ⅱ to Ⅳ was reduced. However, only five provinces showed decreased yield-scaled ESV.(5) The guidance and encouragement of local governments played an important role in the protection of the ESV of paddy field. The results of empirical research showed that 90.6% of total 383 respondents were willing to pay the ecological compensation for paddy field. The mean WTP (willingness to pay) is 0.54 yuan/kg. Above half of the respondents would like to pay the ecological compensation in the purchase of rice grain. The WTP positively correlated with the distance of resident to paddy field, the number of party numbers in the family, perception of environment protection, the number of received services of paddy field, and the awareness of the protection of paddy field. However, WTP showed on significant correlation with the gender, age, occupation, and awareness of food security.(6) Based on the above results, we analyzed the ecological compensation region, basic principles, compensation guideline, compensation pathway, and encouragement mechanism for paddy field. The compensation regions can be divided into rice planting areas on mountains and hills, on the plain, and on the shoaly land. The basic principles of compensation were equitable, differential, progressive, and project based. The pathways for compensation are government and market pathways. The government pathways include public ecological compensation policy and green subsidy. And the market pathways include income feedback and carbon trade. The guideline of ecological compensation should be determined based on the ESV of paddy field. More attention should be paid on the encouragement of government, the public, and farmers to construct a whole link to protect the ESV of paddy field. |
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