Predicting the ecological consequences of mega hydroelectric dams on vertebrate assemblages in lowland tropical forests

大型水电大坝的建设是目前低地热带森林栖息地丧失的最重要驱动因素之一，在那里，每单位淹没面积产生的兆瓦级水电的比例是出了名的低。迄今为止在巴西亚马逊地区建造的9座大型水电大坝至少淹没了66.2万公顷的原始森林，到2022年将再建造10座大型水坝。水电能源部门促进了森林动植物的广泛侵蚀，因为大片森林变成了嵌在不合适的淡水基质中的岛屿，以及整个邻近水库地区的森林砍伐率很高。随着水电投资的不断增加，评估大型水坝对森林生物多样性持续性的影响已成为热带森林保护的一个重要研究重点。巴尔比纳水电站（BHD）在亚马逊中部的环境影响被广泛认为是灾难性的；在建设时（1986年）估计电力供应的50%以下，现在以236,000公顷的连续森林为代价产生，这些森林被减少到约3,500个岛屿的群岛。然而，这个实验景观提供了一个独特的机会来研究生物对栖息地破碎化和隔离的反应。除了长期的放松时间，与其他破碎的景观相比，巴尔比纳大坝有几个优势，包括大量的复制岛屿，均匀的栖息地矩阵，有效的保护伐木和狩猎，以及来自管理库区的Uatumã生物保护区的部分后勤支持。在这里，我们建议研究陆地和树栖脊椎动物种群（哺乳动物、鸟类和爬行动物）如何应对巴尔比纳水库景观结构在隔离后的剧烈变化，以及森林干扰和森林隔离的协同作用。定量调查将在32个地点进行，使用7种采样技术的组合：样线普查，点计数，相机陷阱，轨道调查，封闭的轨道站，犰狳洞穴计数，以及昼夜和夜间动物的自动数字记录。物种持久性和群落结构模式将被量化，并与生境结构和组成（森林基底面积、冠层间隙分数、冠层高度、林下密度、活/死树密度和植物区系多样性）以及不同的斑块和景观指标（岛屿大小、形状、隔离度、土地覆盖）相关。森林冠层断裂将使用数字半球面照片和高分辨率卫星图像进行评估。本研究将记录真实湖相岛屿系统中脊椎动物群落的局部灭绝模式，并利用修正的物种-区域关系预测整个巴尔比纳群岛的物种丰富度和组成。使用“分析工具包”，本研究的结果还将为其他亚马逊河流域计划中的水电大坝的施工前环境影响评估和许可标准提供信息，前提是大坝位置和最高水位已知，并且可以提供上游洪水地区的数字高程（DE）数据。这将有助于开发一个预测框架，利用该框架可以评估水电发电和生物多样性侵蚀之间的权衡，为一系列拟议的水电大坝项目选址。

The construction of major hydroelectric dams is one of the most important current drivers of habitat loss in lowland tropical forests, where the ratio of megawatts of hydropower produced per unit of flooded area is notoriously low. At least 662,000 ha of primary forests were inundated by the nine mega-hydroelectric dams constructed to date across the Brazilian Amazon, and 10 additional major dams will be built by 2022. The hydroelectric energy sector promotes widespread erosion of forest fauna and flora due to conversion of large tracts of forest into islands embedded within a unsuitable freshwater matrix and high deforestation rates throughout the neighbouring reservoir areas. Given escalating investments in hydropower, assessing the effects of mega-dams on forest biodiversity persistence has become a high research priority in tropical forest conservation. The environmental impact of the Balbina Hydroelectric Dam (BHD) in the Central Amazon has been widely considered to be disastrous; <50% of the estimated power supply at the time of construction (1986) is now generated at the expense of 236,000ha of continuous forests that were reduced to an archipelago of ~3,500 islands. However, this experimental landscape provides a unique opportunity to examine biotic responses to habitat fragmentation and isolation. In addition to the long-term relaxation time, the Balbina Dam presents several advantages compared to other fragmented landscapes including a large number of replicate islands, a homogeneous habitat matrix, effective protection from logging and hunting, and partial logistical support from the Uatumã Biological Reserve which manages the reservoir area. Here, we propose to examine how both terrestrial and arboreal vertebrate populations (mammals, birds and reptiles) respond to drastic post-isolation alteration in landscape structure in the Balbina reservoir, and the synergistic interaction of forest disturbance and forest isolation. Quantitative surveys will be conducted at 32 sites using a combination of seven sampling techniques: line-transect censuses, point-counts, camera trapping, track-surveys, enclosed track stations, armadillo burrow counts, and automated digital recordings of the diurnal and nocturnal fauna. Patterns of species persistence and community structure will be quantified and related to habitat structure and composition (forest basal area, canopy gap fraction, canopy height, understorey density, density of live/dead trees and floristic diversity) and different patch and landscape metrics (island size, shape, isolation, land cover). Forest canopy fracture will be assessed using digital hemispherical photographs coupled with high resolution satellite images. This study will document the patterns of local extinction in vertebrate assemblages within a true lacustrine island system and predict species richness and composition across the entire Balbina archipelago using modified species-area relationships. Using an 'analytical toolkit', results from this study will also inform pre-construction environmental impact assessments and licensing standards of planned hydroelectric dams projected for other Amazonian river basins, provided that the dam location and maximum water-level are known and digital elevation (DE) data for the upstream flooded area can be made available. This will allow the development of a predictive framework with which the tradeoffs between hydropower generation and biodiversity erosion can be evaluated for a range of proposed hydroelectric dam project sites.