Hundreds of shallow lakes in the Yangtze River floodplain, once the rarely-existing resources bank for freshwater species in the world, were previously connected with the mainstream of the Yangtze River, forming an integrative ecosystem called “potamo-lacustrine complex ecosystem” . However, since the 1950s, most lakes were disconnected from the Yangtze River by dams or sluice gates, leaving few connected lakes at present. The river-lake disconnection reduced species diversity of Yangtze lakes by 20% to 50%, resulting in serious degradation of biological resources. Therefore, restoration and protection of river-connected lakes plays an important role in maintaing the Yangtze River’s floodplain biodiversity. Then, what is the minimum protected area of river-connected lakes? 

Dr. LIU Xueqin and Prof. WANG Hongzhu from Institute of Hydrobiology, Chinese Academy of Sciences (IHB) answered this question in a paper entitled “Estimation of minimum area requirement of river-connected lakes for fish diversity conservation in the Yangtze River floodplain”(2010, 16: 932-940) (http://onlinelibrary.wiley.com/doi/10.1111/j.1472-4642.2010.00706.x/abstract ), which was recently published on Diversity and Distributions, an authoritative international journal of conservation biogeography.  

Based on the collected data on fish biodiversity for Yangtze floodplain lakes, IHB researchers compared different models used to estimate the minimum area requirement of river-connected lakes for fish diversity conservation in the Yangtze River floodplain. In comparison with the species–area model, they found that the cumulative species–area is more suitable for estimating the minimum protected area. Dealing with the conservation of total fish fauna of the mid-lower Yangtze lakes, the minimum protected area of river-connected lakes was estimated to be 14,400 km2. This is the world’s first attempt to estimate the minimum protected area of river-connected lakes in floodplain and the first suggestion that cumulative species–area model might be more suitable for reserve design of ecosystems with high connectivity among regions such as floodplains.  As the existing river-connected lake area in the Yangtze River floodplain, mainly contributed by two large-sized lakes, Lake Poyanghu and Lake Dongtinghu, is only about 5500 km2, at least 8900 km2 of disconnected lakes need to be reconnected with the Yangtze mainstream.  

As an integrated ecosystem, the Yangtze River floodplain should be restored and protected as part of a restoration strategy for the whole river basin. IHB researchers recommend that at least 14,400 km2 of river-connected lakes should be preserved for total fish conservation in the Yangtze floodplain lakes. They also propose that commercial fishing in the Yangtze and connected lakes should be banned all the year round, and a core protected area, where all human activities are forbidden, should be demarcated. To address the issues as how to determine the optimum selection of reconnected lakes and their spatial pattern in the landscape, and how to reconnect them with the Yangtze mainstream, further study on life history processes of fishes and environmental flow requirements of fishes and related organisms (e.g. macrophytes, benthos) in the river-floodplain ecosystem is needed. As tentative measures to meet the urgent need of fish conservation, researchers may first construct a restoration framework on the basis of the fish diversity patterns, ecological health and spatial distribution patterns of disconnected lakes and then reconnect these lakes with the Yangtze mainstream as frequently as possible. 

The research was funded by the State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences and World Wild Fund for Nature.