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Multi-scale assessment of human-induced changes to Amazonian instream habitats
Citation:
Leal, C., P. Pompeu, T. Gardner, R. Leitao, R. Hughes, Phil Kaufmann, J. Zuanon, F. de Paula, S. Ferraz, J. Thomson, R. MacNally, J. Ferreira, AND J. Barlow. Multi-scale assessment of human-induced changes to Amazonian instream habitats. LANDSCAPE ECOLOGY. Springer, New York, NY, 31(8):1725-1745, (2016).
Impact/Purpose:
Adaptations the USEPA’s National Aquatic Resource Survey (NARS) designs, field methods, and approaches for assessing ecological condition have been applied in state and basin stream surveys throughout the U.S., and also in countries outside of the U.S. These applications not only provide valuable tests of the NARS approaches, but generate new understandings of natural and anthropogenic controls on biota and physical habitat in streams. Results from applications in Brazil, for example, not only aid interpretation of the condition of Brazilian streams, but also refine approaches for interpreting aquatic resource surveys in the U.S. and elsewhere. In this article, the authors describe a survey of the physical and chemical habitat of small streams across a gradient of anthropogenic disturbances related to land-use change (LUC) in two large basins in the Amazon River drainage in 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 improved significantly in recent decades, tropical aquatic systems have received far less research attention, with the majority of existing work concentrated in a small number of well-studied regions, such as Costa Rica, Puerto Rico, Hong Kong and Australia. The authors conclusions highlight the importance of both local riparian and catchment-scale forest cover in shaping instream physical environments, but also underscore the importance of other land use changes and activities, such as road crossings and upstream agriculture intensification. Similar to findings in temperate ecoregions, these results reinforce the importance of catchment-wide management strategies to protect stream ecosystem integrity. Furthermore, the research described in the manuscript is a demonstration of the utility of NARS field methods to assess the effects of human activities on instream physical and chemical habitat. The analytical framework applied to NARS-style field data serves a model that could be applied with NARS data to make similar diagnostic assessments in the U.S.
Description:
Context: Land use change and forest degradation have myriad effects on tropical ecosystems. Yet their consequences for low-order streams remain very poorly understood, including in the world´s largest freshwater basin, the Amazon.Objectives: Determine the degree to which physical and chemical characteristics of the instream habitat of low-order Amazonian streams change in response to past local- and catchment-level anthropogenic disturbances. Methods: To do so, we collected field instream habitat (i.e., physical habitat and water quality) and landscape data from 99 stream sites in two eastern Brazilian Amazon regions. We used random forest regression trees to assess the relative importance of different predictor variables in determining changes in instream habitat response variables.
