Soil Erosion from Agriculture and Mining: A Threat to Tropical Stream Ecosystems

Wantzen, Karl M.; Mol, Jan H.

doi:10.3390/agriculture3040660

Cited by 106 publications

(64 citation statements)

References 56 publications

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“…Although RIL preserves the strip of riparian vegetation established by the Brazilian Forestry Code and by technical logging guidelines for the Amazon region (Sabogal et al ., ), our results reinforce the idea that changes in stream habitat structure might occur not only due to local changes but also because of changes in the land cover elsewhere in the catchment (O'Neill, Johnson & King, ; Feld, ; Macedo et al ., ). Previous studies have demonstrated that aquatic ecosystems in areas experiencing RIL may be indirectly affected by the opening of logging roads causing stream fragmentation and increasing erosion and input of fine sediment (Dias et al ., ; Wantzen & Mol, ; Allard et al ., ). In this study, the physical habitat did not show an indication of recovery even a decade after RIL, with logged areas showing significant differences in tree canopy cover, channel morphology and water physical–chemical feature when compared to unlogged areas.…”

Section: Discussionmentioning

confidence: 99%

Effects of reduced‐impact logging on physical habitat and fish assemblages in streams of Eastern Amazonia

et al. 2016

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Summary Reduced‐impact logging (RIL) has been considered as the main activity of forestry management in the Amazon. However, little is known of the effects of RIL on the region's ecosystems or in their biodiversity, and such information would be useful to inform forest management. Accordingly, this study aimed to investigate the effects of RIL on physical habitat and fish assemblages in Eastern Amazonia streams. We predicted that changes caused by RIL affect stream habitat, leading to a loss of diversity and changes in species composition with a predominance of generalist species. We sampled 13 streams in basins dominated by native vegetation without evidence of logging activity (unlogged areas) and 23 in areas that had been logged at different times between 2001 and 2011. Stream physical habitat structure was characterized using a standardized protocol, and the abundance, richness and composition of fish assemblages were assessed. Biotic and abiotic data were compared between unlogged and logged areas, and among streams in areas with different logging years. The relationship between the stream habitat structure and fish assemblages was assessed using a distance‐based linear model using a forward procedure, followed by application of the Akaike information criterion. Variations in tree canopy cover, channel morphology, water temperature and dissolved oxygen and conductivity accounted for most of the differences in habitat characteristics between unlogged and logged areas. A total of 53 fish species was collected, belonging to 20 families and 6 orders. Fish abundances did not vary consistently between streams in unlogged areas and those that had undergone RIL, and showed minor evidence of species‐specific changes in response to logging years. Likewise, there were no obvious differences in species richness, composition and biomass between logged and unlogged sites, regardless of logging years. RIL in Eastern Amazonia is performed in compliance with technical guidelines, but this practice has resulted in changes in stream physical habitat. Nonetheless, in the headwater streams that we sampled, the effects of RIL on fish assemblages were minor.

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Section: Discussionmentioning

confidence: 99%

Effects of reduced‐impact logging on physical habitat and fish assemblages in streams of Eastern Amazonia

et al. 2016

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“…The highest aggregate stability was related to Cerrado, pastures and eucalyptus plantations; interestingly, the stable aggregates were not related to notill soybean systems (although no-till accumulated the most organic carbon). Likewise, Wantzen and Mol (2013) pointed out that despite of direct planting and other measures (e.g., construction of contour lines), erosion is still a problem. According to our findings, accelerated erosion is likely to occur in the future.…”

Section: Discussion Of the Combined Effects Of Water And Land Degradamentioning

confidence: 99%

The Brazilian Cerrado: assessment of water and soil degradation in catchments under intensive agricultural use

et al. 2014

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The Brazilian Cerrado is recognized as one of the most threatened biomes in the world, as the region has experienced a striking change from natural Cerrado vegetation to intense cash crop production. This paper reviews the history of land conversion in the Cerrado and the development of soil properties and water resources under past and ongoing land use. We compared soil and water quality parameters from different land uses considering 80 soil and 18 water studies conducted in different regions across the Cerrado to provide quantitative evidence of soil and water alterations from land use change. Following the conversion of native Cerrado, significant effects on soil pH, bulk density and available P and K for croplands and less-pronounced effects on pastures were evident. Soil total N did not differ between land uses because most of the sites classified as croplands were nitrogen-fixing soybeans, which are not artificially fertilized with N. In contrast, water quality studies showed nitrogen enrichment in agricultural catchments, indicating fertilizer impacts and potential susceptibility to eutrophication. Regardless of the land use, P is widely absent because of the high-fixing capacities of deeply weathered soils and the filtering capacity of riparian vegetation. Pesticides, however, were consistently detected throughout the entire aquatic system. In several case studies, extremely high-peak concentrations exceeded Brazilian and European Union (EU) water quality limits, which were potentially accompanied by serious health implications. Land use intensification is likely to continue, particularly in regions where less annual rainfall and severe droughts are projected in the northeastern and western Cerrado. Thus, the leaching risk and displacement of agrochemicals are expected to increase, particularly because the current legislation has caused a reduction in riparian vegetation. We conclude that land use intensification is likely to seriously limit the Cerrado's future regarding both agricultural productivity and ecosystem stability. Because only limited data are available, we recommend further field studies to understand the interaction between terrestrial and aquatic systems. This study may serve as a valuable database for integrated modelling to investigate the impact of land use and climate change on soil and water resources and to test and develop mitigation measures for the Cerrado.

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“…Indeed, goldmining is particularly widespread in South America (Veiga 1997;Alvarez-Berríos and Aides 2015), and is currently experiencing a dramatic increase due to the rise of gold prices that pushes illegal miners to exploit remote and pristine sites throughout the Amazon region (Hammond et al 2007;Alvarez-Berríos and Aides 2015). For example, in the Guiana shield, a threefold increase in the number of impacted streams was recorded in the last decade, representing more than 26,000 km of impacted streams (Hammond et al 2007;World Wildlife Fund Guianas 2012).…”

Section: Discussionmentioning

confidence: 99%

Effect of reduced impact logging and small-scale mining disturbances on Neotropical stream fish assemblages

et al. 2015

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Deforestation and mining are recognized as major threats to Amazonian biodiversity, but, in addition to the well known impacts of clear cutting and industrial mining, the impact of cryptic threats such as illegal smallscale gold-mining and reduced impact logging remain little known. Here, we quantify the impact of those cryptic disturbances on a set of 201 sites dispersed throughout French Guiana. The fish assemblages of 139 pristine forest sites were compared to 16 sites subjected to reduced impact logging (i.e. selective logging), 24 sites with ongoing small-scale gold-mining and 22 sites formerly mined for gold. Controlling for the environmental variability between sites showed the significant structuring effect of all disturbances on fish taxonomic structure, with a marked impact of gold-mining. This effect was of strong magnitude and remained significant after mining activity ceased. In contrast, the reduced impact logging effect remains of low magnitude, although significant. From a functional point of view, gold-mining drives species assemblages towards a decrease in the richness of small-sized stream habitat specialist species and favours larger ubiquitous species living in both streams and rivers. Reduced impact logging effect was slighter, and negatively affected only the richness of phytophagous species. These results, encompassing a variety of hydrographic basins, unambiguously show the detrimental effect of small-scale gold-mining on fish assemblages as well as the slight effect of reduced impact logging. Since gold-mining is one of the most widespread threats throughout the Amazonian region, particular care should be given to controlling this, often illegal, activity.

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Soil Erosion from Agriculture and Mining: A Threat to Tropical Stream Ecosystems

Cited by 106 publications

References 56 publications

Effects of reduced‐impact logging on physical habitat and fish assemblages in streams of Eastern Amazonia

Effects of reduced‐impact logging on physical habitat and fish assemblages in streams of Eastern Amazonia

The Brazilian Cerrado: assessment of water and soil degradation in catchments under intensive agricultural use

Effect of reduced impact logging and small-scale mining disturbances on Neotropical stream fish assemblages

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