三峡库区蓄水前后农田生态系统服务与环境压力分析

Analysis of farmland ecosystem services and environmental pressures in the Three Gorges Reservoir Area,before and after impoundment

农田生态系统是人类赖以生存的基础,重大工程影响下农田生态系统服务的响应与反馈对指导工程影响区的社会经济发展具有重要意义。基于三峡工程蓄水前后(2002,2011)的农业生产数据,评估了库区农田生态系统服务价值,并对其在蓄水前后的变化特征与环境压力进行了分析。结果表明:(1)三峡库区蓄水后,农田生态系统各项服务价值均增加,总价值增加了16.81%,增加部分主要为产品供给、休闲旅游和气体调节,相对于生产功能与生活功能,生态功能价值增加幅度较小;(2)总价值的变化是自然与包括三峡工程在内的人类活动综合影响的结果,其增加原因主要与常用耕地面积增加、种植结构调整、化肥农药施用强度增加,以及休闲旅游发展和科研投入加大有关,部分区县,尤其是常用耕地面积下降的区县,种植结构调整、化肥农药施用强度的增加起主导作用,按1990年不变价计算,库区蓄水淹没耕地损失的农田生态系统服务价值约为4.24亿元/a,其中产品供给价值1.37亿元/a;(3)化肥农药施用强度增加,化肥施用增产效益下降,是维持与提高库区农田生态系统产品供给服务所带来的环境压力,而农田生态系统服务除受到化肥农药施用强度增加对其自身的抑制外,还受到总人口增加与农业人口减少、耕地资源逐年减少和蓄水淹没高质量耕地的制约。

Farmland ecosystems are fundamental to human survival, and the response and feedback of farmland ecosystem services to the impacts of major projects are of vital importance for guiding regional social and economic development. Based on agricultural production data of the Three Gorges Reservoir Area （TGRA） before and after impoundment （ 2002, 2011 ）, the Ecosystem Service Value （ESV） of farmland in the TGRA was estimated; changes in its characteristics and environmental pressures were also discussed. The results show that （ 1 ） after impoundment, each ESV of farmland increased, and the Total Value increased by 16.81%; the values of product supply, leisure tourism and gas regulation dominated the increase of the Total Value; compared with product supplying and life ensuring, the value of ecological regulating showed a relatively small increase. （2） The change in the Total Value was the result of natural and human activities, including the Three Gorges Project; the increase in Regularly Cultivated Land, planting structure adjustment, increased use intensity of chemical fertilizer and pesticide, development of leisure tourism, and increased scientific research input were the major reasons for the increase of the Total Value. For some counties, especially those with decrease in Regularly Cultivated Land, planting structure adjustment and the increased use intensity of chemical fertilizer and pesticide might be the main reasons for the increased farmland ESV. After being normalized to the consolidated value of year 1990, the inundation of cultivated land decreased the farmland ESV by 424 million yuan per year, among which the value of product supply was 137 million yuan peryear. （3） The increased use intensity of chemical fertilizer and pesticide, and the decreased contribution of chemical fertilizer to crop yield were the environmental pressures imposed by maintaining and promoting the product supply of the farmland ecosystem in the TGRA. Moreover, the farmland ESV was not only influenced by the above- mentioned environmental pressures, but also by the increase in population, the decrease in agricultural population, the decrease in land resources, and the inundation of high-quality cultivated land.