Rai Anu, Bashir Tawqir, Lagunes-Díaz Elio Guarionex, Shrestha Bibek
Department of Environmental Science and Engineering, School of Science Kathmandu University Dhulikhel Nepal.
Sustainability and Environmental Studies Endeavor (SENSE) Kathmandu Nepal.
Ecol Evol. 2023 May 21;13(5):e10106. doi: 10.1002/ece3.10106. eCollection 2023 May.
Physiographic and hydrologic complexities play major role in determining the habitat suitability for river dolphins. However, dams and other water development structures alter hydrologic regimes that degrade habitat conditions. For the three extant species of obligate freshwater dolphins, namely: Amazon dolphin (), Ganges dolphin (), and Indus dolphin (), the threat is high as dams and water-based infrastructure dotted throughout their distribution range impact dolphin populations by restricting their movement. But there is also evidence of localized increase in dolphin population in certain segments of habitats affected by such hydrologic alterations. Hence, the impacts of hydrologic alterations on dolphin distribution are not as binary as it seems. We aimed to ascertain the role of hydrologic and physiographic complexities in determining the distribution of the dolphins in their geographic ranges using density plot analysis and also to understand how hydrologic alterations in the rivers affect their distribution using a combination of density plot analysis and review of literature. The influence of some of the study variables such as distance to confluence and sinuosity was similar across species-for instance, all three dolphin species preferred slightly sinuous river segments and habitats near confluences. However, varying influences across species were observed for some other variables such as river order and river discharge. We assessed 147 cases of impacts of hydrological alterations on dolphin distribution by categorizing the reported impacts in nine broad types out of which habitat fragmentation accounted for the majority of the impacts (35%) followed by habitat reduction (24%). These endangered species of freshwater megafauna will experience further intensified pressures as more large-scale hydrologic modifications such as damming and diversion of rivers are underway. In this context, basin-scale water-based infrastructural development planning should take into consideration the salient ecological requirements of these species to ensure their long-term survival.
地形和水文的复杂性在决定河豚的栖息地适宜性方面起着主要作用。然而，水坝和其他水利开发设施改变了水文状况，使栖息地条件恶化。对于三种现存的专性淡水豚类物种，即亚马逊河豚（ ）、恒河豚（ ）和印度河豚（ ）来说，威胁很大，因为遍布其分布范围的水坝和水利基础设施通过限制其活动影响了豚类种群。但也有证据表明，在受此类水文变化影响的某些栖息地区域，豚类种群出现了局部增长。因此，水文变化对豚类分布的影响并非像看上去那样简单直接。我们旨在通过密度图分析确定水文和地形复杂性在决定豚类在其地理范围内分布中的作用，并通过结合密度图分析和文献综述来了解河流中的水文变化如何影响它们的分布。一些研究变量，如到汇合处的距离和弯曲度，对不同物种的影响相似——例如，所有三种豚类物种都更喜欢略微弯曲的河段和汇合处附近的栖息地。然而，对于其他一些变量，如河流等级和流量，不同物种的影响有所不同。我们通过将报告的影响分为九大类来评估147例水文变化对豚类分布的影响，其中栖息地破碎化占影响的大多数（35%），其次是栖息地减少（24%）。随着更多大规模的水文改造，如筑坝和河流改道正在进行，这些濒危的淡水巨型动物物种将面临进一步加剧的压力。在这种背景下，流域尺度的水利基础设施发展规划应考虑这些物种的显著生态需求，以确保它们的长期生存。
