Caroline C. Arantes

Balancing hydropower and biodiversity in the Amazon, Congo, and Mekong

Basin-scale planning is needed to minimize impacts in mega-diverse rivers The worlds most biodiverse river basins—the Amazon, Congo, and Mekong—are experiencing an unprecedented boom in construction of hydropower dams. These projects address important energy needs, but advocates often overestimate economic benefits and underestimate far-reaching effects on biodiversity and critically important fisheries. Powerful new analytical tools and high-resolution environmental data can clarify trade-offs between engineering and environmental goals and can enable governments and funding institutions to compare alternative sites for dam building. Current site-specific assessment protocols largely ignore cumulative impacts on hydrology and ecosystem services as ever more dams are constructed within a watershed (1). To achieve true sustainability, assessments of new projects must go beyond local impacts by accounting for synergies with existing dams, as well as land cover changes and likely climatic shifts (2, 3). We call for more sophisticated and holistic hydropower planning, including validation of technologies intended to mitigate environmental impacts. Should anything less be required when tampering with the worlds great river ecosystems?

Environmental influences on the distribution of arapaima in Amazon floodplains

This study investigated the environmental factors influencing the distribution of the endangered arapaima (Arapaima spp.) in floodplains of the Amazon. The abundance of arapaima was found to be positively related to the area and depth of the water column, and hence volume of lakes. Greater depth of water column also was related positively with the abundance and presence of arapaima in connecting channels. The abundance of arapaima was positively related to the connectivity of the lake with other water bodies. The principal reason for arapaima to prefer habitats that are deep, large, and connected to other water bodies appears to be increased survival through lower susceptibility to extreme drought events and increased mobility and availability of food resources. Deeper, larger, and more connected lakes and connecting channels sustain greater arapaima populations; they can now be used to prioritize conservation efforts.

Relationships between forest cover and fish diversity in the Amazon River floodplain

1.Habitat degradation leads to biodiversity loss and concomitant changes in ecosystem processes. Tropical river floodplains are highly threatened by land cover changes and support high biodiversity and important ecosystems services, but the extent to which changes in floodplain land cover affect fish biodiversity remains unknown. 2.We combined fish and environmental data collected in situ and satellite-mapped landscape features to evaluate how fish species with different ecological strategies and assemblage structures respond to deforestation in floodplains of the Amazon River. We surveyed 462 floodplain habitats distributed along a gradient of land cover, from largely forested to severely deforested. Rather than analyze only taxonomic metrics, we employed an integrative approach that simultaneously considers different aspects of fish biodiversity (i.e., beta diversity and taxonomic and functional assemblage structure) to facilitate mechanistic interpretations of the influence of land cover. 3.Spatial patterns of fish biodiversity in tropical floodplain rivers were strongly associated with forest cover as well as local environmental conditions linked to landscape gradients. Several species and functional groups defined by life history, feeding, swimming/microhabitat-use strategies were positively associated with forest cover. Other species, including some that would usually be considered habitat generalists and species directly dependent on autochthonous resources (e.g., planktivores), were most common in areas dominated by herbaceous vegetation or open-water habitats associated with the opposite extreme of the forest cover gradient. Beta-diversity and the degree of uniqueness of species combinations within habitats were also positively associated with forest cover. 4.Synthesis and applications. Our results, demonstrating that spatial patterns of fish biodiversity are associated with forest cover, indicate that deforestation of floodplains of the Amazon River results in spatial homogenization of fish assemblages and reduced functional diversity at both local and regional scales. Floodplains worldwide have undergone major land cover changes, with forest loss projected to increase during the next decades. Conserving fish diversity in these ecosystems requires protecting mosaics of both aquatic habitats and floodplain vegetation, with sufficient forest cover being critically important. This article is protected by copyright. All rights reserved.

Erratum to: Modeling population dynamics and conservation of arapaima in the Amazon

The original article is published with incorrect values in the first paragraph below the subtitle ‘‘Basin-wide production.’’ The correct version of the text is given below for your reading. ‘‘On a per hectare basis, these values are 0.33, 0.31, and 0.04 indiv. ha, respectively, and they offer a comparative baseline to assess the health of arapaima populations elsewhere (e.g., community-based management).’’