淡水生物多样性保护背景下长江流域河流干扰度分析及展望

Analysis and Prospect of River Disturbance Index in the Yangtze River Basin Under the Background of Freshwater Biodiversity Protection

全球正面临着严峻的淡水生物多样性危机,维持河流的自然流淌性是国际公认的保护淡水生物多样性的重要措施。长江作为中国第一大河,是世界淡水生物多样性最丰富的水系,但水生态系统退化已成为其最突出的问题之一。识别长江流域自然流淌河流的数量、分布及与淡水生物多样性的关系对于长江大保护具有重要意义。本研究针对长江流域的宏观空间尺度,采用“河流干扰指数”方法,识别出长江流域潜在自然流淌河流长度约占流域干支流总长度的24%,即7311 km,其流域面积占长江流域总面积的21.6%,约39万平方公里。综合相关文献,得到上述研究结果与以鱼类、两栖及底栖动物为代表的长江流域现有淡水生物多样性及与长江流域自然保护地体系的关系。最后探讨长江流域面向淡水生物多样性保护未来亟待开展的工作,并分析河流干扰度评价与自然流淌河流保护的应用前景。

The world is facing a severe freshwater biodiversity crisis.Maintaining free-flowing status of rivers is one of the internationally recognized important measures to protect freshwater biodiversity.As the largest river in China,the Yangtze River is one of the water systems with the richest freshwater biodiversity in the world,but the degradation of the water ecosystem has become one of its most prominent problems.Identifying the number and distribution of free-flowing rivers in the Yangtze River watershed and their relationship with freshwater biodiversity have important meaning for the conservation of the Yangtze River.The concept of free-flowing rivers(FFRs)proposed by the World Wide Fund(WWF)for nature means that“A free-flowing river or stretch of river occurs where natural aquatic and riparian ecosystem functions and services are largely unaffected by anthropogenic changes to fluvial connectivity,allowing an unobstructed exchange of material,species and energy within the river system and beyond.”.The two key measures of protecting free-flowing rivers and restoring river connectivity play an important supporting role in freshwater biodiversity.The method of river disturbance index(RDI)is derived from the concept of wilderness continuum spectrum and River Continuum Concept(RCC)theory.The changes in hydrology,geomorphology and biological processes of rivers are considered to be the key to identify the natural flow state of rivers.The river disturbance index emphasizes the recognition of human factors that change the natural process of the river from the perspective of integrated watershed management.Based on the macro-spatial scale of the Yangtze River,this study uses the method of“river disturbance index”to identify t hat t he length of t he potential f ree-flowing r ivers.T he steps include:(1)Collect spatial data influencing the free-flowing characteristics of rivers in the Yangtze River,establish a Data set containing disturbance of river hydraulic facilities and land use in watershed,and calculate the weight;(2)Based on the superposition of internal and external river disturbance in each sub basin of the Yangtze River,the total river disturbance index in the sub basin is calculated.By this method,we can make the continuous spectrum of river disturbance index.At both ends of the continuum spectrum are completely undisturbed state(RDI=0)to serious disturbed state(RDI=1).By setting a reasonable threshold,the free-flowing river can be identified.In the end,it’s found out that the length of the potential free-flowing rivers accounts for about 24%(7311 kilometers)of the total Yangtze River watershed,and its watersheds area accounts 21.6%(390000 square kilometers).According to the analysis results,the middle and lower reaches of the Yangtze River watershed are affected by human activities such as water pollution,water conservancy projects and river channel concretization,which indicates high level of human disturbance.The river continuity and the integrity of water ecosystem are greatly threatened,and the freshwater ecosystem is greatly affected.Typical rivers with low human disturbance and potential free-flowing rivers are mainly located in the upper reaches of the trunk and tributaries of the Yangtze River watershed.On the basis of literature review,the relationship between the above research results and the existing freshwater biodiversity in the Yangtze River watershed represented by fish,amphibians and benthic animals and the natural protected area system in the Yangtze River watershed was obtained.There are different types of protected areas and management administrative systems in the Yangtze River watershed.Different types of protected areas have different management standards.It is difficult to unify control policies for freshwater biodiversity and realize systematic protection in the whole watershed.There is still a big gap in the protection of rare aquatic organisms At last,the urgent work to be done in the future for the protection of freshwater biodiversity in the Yangtze River is discussed,the following conclusions are obtained:(1)the freshwater biodiversity in the Yangtze River watershed needs to pay more attention to the protection of tributaries,and tries to protect and restore the free-flowing rivers in the upper reaches of tributaries of highly disturbed rivers.And fill the vacancy of the current nature protected areas;(2)it is necessary to further focus on key vacant areas,establish a reasonable spatial planning scheme that balances the effectiveness of ecological protection and social and economic costs,and learn from internationally mature policies and management systems;(3)further study the application of free-flowing rivers protection and river management methods,and incorporate the theory,technology and management into the comprehensive watershed management strategy.