Citation:

Leal, C., J. Barlow, T. Gardner, R. Hughes, R. Leitao, R. Mac Nally, Phil Kaufmann, S. Ferraz, J. Zuanon, F. de Paula, J. Ferreira, J. Thomson, G. Lennox, E. Dary, C. Röpke, AND P. Pompeu. Is environmental legislation conserving tropical stream faunas? A large-scale assessment of local, riparian and catchment-scale influences on Amazonian fishes. Journal of Applied Ecology. Blackwell Publishing, Malden, MA, 55(3):1312-1326, (2017).

Impact/Purpose:

Using adaptations of the US EPA’s National Aquatic Resource Survey (NARS) designs and methods, Leal and colleagues sampled 83 low-order streams distributed across three sub-basing of the Amazon River within two regions of Brazil. Similar adaptations of NARS designs, field methods, and approaches for assessing ecological condition have been applied in state and basin stream surveys throughout the U.S. and internationally, but have been especially innovative in Brazil. These applications are not only valuable tests of the NARS approaches, but contribute to environmental science, resource management, and conservation of biodiversity through new understandings of natural and anthropogenic controls on biota and physical habitat in streams. Results from these innovative applications in Brazil, for example, not only aid our understanding of the effects of landscape fragmentation and deforestation on biodiversity in Brazilian streams, but also refine approaches for analyzing and interpreting aquatic resource surveys in the U.S. and elsewhere. In this article, the authors used NARS methods to collect fish assemblage and physical habitat data from small streams across a gradient of anthropogenic disturbances related to land-use change (LUC) in two large basins in the Amazon River drainage of Brazil. LUC is one of the most important factors altering Earth’s ecosystem, affecting both global biodiversity and the conservation of ecosystem services. The impacts of LUC are of great concern in the tropics, and particularly in the Amazon basin, where the expansion of agricultural and infrastructure development usually occur at the expense of species-rich natural habitats. While our understanding of the impacts of LUC on terrestrial tropical systems has increased, the majority of existing work has been concentrated in a small number of well-studied regions, such as Costa Rica, Puerto Rico, Hong Kong and Australia. Leal and colleagues collected 25,526 fish from 143 species. For the 52 species that were analyzed in detail, instream habitat features explained markedly more variability in their presence and abundance (15 to 19%) than did riparian (2-12%), other landscape characteristics (4-13%), and natural covariates (4-11%). With increased disturbance, they detected more individuals of the common species; but lacked sufficient data to model the controls on the presence and abundance of rare species. Considerable variability remained unexplained despite the diverse set of environmental predictor variables measured. Other published work by the same authors has shown that both basin and riparian condition are importance influences on the instream habitat features that they demonstrate to be strong controls on fish presence and abundance in these streams. On that basis, the authors conclude that the current focus on protecting riparian vegetation is insufficient to conserve stream environments and their fish assemblages. They suggest that if our goal is to effectively safeguard the freshwater biota of small tropical streams, conservation efforts must shift towards managing whole basins and drainage networks.

Description:

Tropical agricultural is a major threat to biodiversity worldwide. In addition to the direct impacts of converting native vegetation to agriculture this process is accompanied by a wider set of human-induced disturbances, many of which are poorly addressed by existing environmental legislation and conservation programs. This is particularly the case for freshwater systems, which are often neglected and much less studied than terrestrial systems. We address this knowledge gap using a comprehensive dataset on the ecological integrity of stream systems from the eastern Brazilian Amazon, one of the world´s most active deforestation frontiers. To do so, we examine how the presence and abundance of stream fish are affected differently by natural stream features and human impacts at instream, riparian, and catchment scales. We sampled 83 low-order streams distributed across three river basins and two regions in the state of Pará, Brazil. Overall we collected 25,526 fish from 143 species. For the 52 species that were analyzed in detail, instream habitat features explained markedly more variability in their presence and abundance (15 to 19%) than did riparian (2-12%), other landscape characteristics (4-13%), and natural covariates (4-11%). With increased disturbance, we often detected more individuals of the common species; but we lacked sufficient data to model rare species. Considerable variability remained unexplained despite the diverse set environmental predictor variables measured. Previous research has shown that both basin and riparian condition are importance influences on the instream habitat features that we demonstrate to be strong controls on fish presence and abundance in these streams. On that basis, we conclude that the current focus on protecting riparian vegetation is insufficient to conserve stream environments and their fish assemblages. If our goal is to effectively safeguard the freshwater biota of small tropical streams, conservation efforts must shift towards managing whole basins and drainage networks.

URLs/Downloads:

Record Details: