Biodiversity is essential to human well-being, but people have been reducing biodiversity throughout human history. Loss of species and degradation of ecosystems are likely to further accelerate in the coming years. Our understanding of this crisis is now clear, and world leaders have pledged to avert it. Nonetheless, global goals to reduce the rate of biodiversity loss have mostly not been achieved. However, many examples of conservation success show that losses can be halted and even reversed. Building on these lessons to turn the tide of biodiversity loss will require bold and innovative action to transform historical relationships between human populations and nature.
1. Poyang Lake is the largest freshwater lake in China and is of global importance for the conservation of migratory waterbirds of the East Asian -Australasian Flyway. Recent dam construction on the Yangtze River and its tributaries for agriculture and hydroelectric power has affected the hydrological regimes in downstream lakes. The Three Gorges Dam changed the hydrological regime of downstream lakes by reducing wet season flooding and expanding water storage in the dry season. 2. Despite the critical role of Poyang Lake in regional and global biodiversity conservation and the potential adverse ecological impacts of the Three Gorges Dam on downstream lakes, there have been few studies of the hydrological requirements of wintering waterbirds in the middle Yangtze floodplains. 3. We assembled a predictor matrix including three hydrological variables (annual inflow, maximum water level in high water season or MaxWL and minimum water level in low water season or MinWL) and two climatic variables (annual rainfall and biological cumulative temperature or BioT). Using the predictor matrix and annual waterbird census, we built group-specific generalised additive models (GAM) to investigate how waterbird population variations were related to climatic and hydrological factors in the Poyang Lake National Natural Reserve. We then used the modelled predictor-response curves to identify the optimal lake water levels for each waterbird group. 4. The community-level model selected group and the group-varying-coefficient term of BioT, Inflow and MaxWL as explanatory variables. At group level, tuber eaters and sedge foragers responded positively to BioT and MinWL. Seed eaters, invertebrate eaters and fish eaters responded positively to Inflow and negatively to MaxWL and MinWL. Based on the modelled predictor-response curves, we propose the following optimal water level ranges for Poyang Lake wintering waterbird conservation: a) maximum high water season level should be less than 17.4 m; and b) minimum low water level should be between 8.2 m and 8.8 m.
There are two genera and four species of icefishes in Nanyi Lake, which have been commercially exploited in the past two decades. As result, icefish yield decreased over the years, from the peak of 260 metric tons to 15 metric tons, and this change was highly correlated (t =-3.95, df = 1, p = 0.001) with increased fishing effort. Meanwhile, the size composition of the icefish assemblage dramatically changed, with significantly increased relative abundance of the small icefish category (from 0.06 to 0.91). Furthermore, sampling during the 2001 fishing season was characterized by a progressive decrease in CPUE (by 3.14 times) and an increase in relative abundance (from 0.83 to 0.97) of the smallest icefish, giving direct evidence of the stocks decline and size diminution of icefishes in relation to the commercial fishing effort. Both the historical records and the 200 1 seasonal changes of the icefish stocks indicated that this resource in Nanyi Lake has been overfished and illustrated that small fishes can also be overfished to degradation when they are commercially exploited.
Gravel bars are characteristic components of river landscapes and are increasingly recognized as key sites for many waterbirds, though detailed studies on the ecological function of gravel bars for waterbirds are rare. In this study, we surveyed the endangered Scaly-sided Merganser Mergus squamatus along a 40 km river section of Yuan River, in Central China, for three consecutive winters. We derived the landscape metrics of river gravel bars from geo-rectified fine resolution (0.6 m) aerial image data. We then built habitat suitability models (Generalized Linear Models—GLMs) to study the effects of landscape metrics and human disturbance on Scaly-sided Merganser presence probability. We found that 1) the Scaly-sided Merganser tended to congregate at river segments with more gravel patches; 2) the Scaly-sided Merganser preferred areas with larger and more contiguous gravel patches; and 3) the number of houses along the river bank (a proxy for anthropogenic disturbance) had significantly negative impacts on the occurrence of the Scaly-sided Merganser. Our results suggest that gravel bars are vital to the Scaly-sided Merganser as shelters from disturbance, as well as sites for feeding and roosting. Therefore, maintaining the exposure of gravel bars in regulated rivers during the low water period in winter might be the key for the conservation of the endangered species. These findings have important implications for understanding behavioral evolution and distribution of the species and for delineating between habitats of different quality for conservation and management.
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