SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Amazon Basin

57

Gold mining has rapidly increased in western Amazonia, but the rates and ecological impacts of mining remain poorly known and potentially underestimated. We combined field surveys, airborne mapping, and high-resolution satellite imaging to assess road- and river-based gold mining in the Madre de Dios region of the Peruvian Amazon from 1999 to 2012. In this period, the geographic extent of gold mining increased 400%. The average annual rate of forest loss as a result of gold mining tripled in 2008 following the global economic recession, closely associated with increased gold prices. Small clandestine operations now comprise more than half of all gold mining activities throughout the region. These rates of gold mining are far higher than previous estimates that were based on traditional satellite mapping techniques. Our results prove that gold mining is growing more rapidly than previously thought, and that high-resolution monitoring approaches are required to accurately quantify human impacts on tropical forests.

Concepts: Amazon River, Tropical rainforest, Amazon Basin, Recession, Peru, Tropical and subtropical moist broadleaf forests, Madre de Dios Region, Peruvian Amazon

42

We mapped the inferred long-distance migrations of four species of Amazonian goliath catfishes (Brachyplatystoma rousseauxii, B. platynemum, B. juruense and B. vaillantii) based on the presence of individuals with mature gonads and conducted statistical analysis of the expected long-distance downstream migrations of their larvae and juveniles. By linking the distribution of larval, juvenile and mature adult size classes across the Amazon, the results showed: (i) that the main spawning regions of these goliath catfish species are in the western Amazon; (ii) at least three species-B. rousseauxii, B. platynemum, and B. juruense-spawn partially or mainly as far upstream as the Andes; (iii) the main spawning area of B. rousseauxii is in or near the Andes; and (iv) the life history migration distances of B. rousseauxii are the longest strictly freshwater fish migrations in the world. These results provide an empirical baseline for tagging experiments, life histories extrapolated from otolith microchemistry interpretations and other methods to establish goliath catfish migratory routes, their seasonal timing and possible return (homing) to western headwater tributaries where they were born.

Concepts: Fish, Human migration, Amazon River, South America, Amazon Basin, Andes, Catfish, Peru

41

Eight new species of Charinus Simon, 1892 are described for the Brazilian Amazon, from the states of Pará (C. bichuetteae sp. n., C. bonaldoi sp. n., C. carajas sp. n., C. ferreus sp. n., C. guto sp. n. and C. orientalis sp. n.) and Amazonas (Charinus brescoviti sp. n. and C. ricardoi sp. n.). All new species can be differentiated from the other species of the genus by the number of pseudo-articles in basitibia IV, the presence/absence of median eyes, and the shape of the female gonopod. Brazil now becomes the country with the largest diversity of Amblypygi in the world, with 25 known species. Half of the new species described here have a high degree of endangerment: C. bichuetteae sp. n. is threatened by the flood caused by the hydroelectric dam of Belo Monte, and C. carajas sp. n., C. ferreus sp. n. and C. orientalis sp. n. are endangered by the iron mining in Carajás municipality and surroundings. The Charinus species here described are endemic to the Amazon Region, so in order to assure their preservation, it is strongly recommended a special care with their habitats (type localities) which are facing increasing rates of destruction and deforestation.

Concepts: Biodiversity, Amazon River, Brazil, Amazon Basin, Manaus, Deforestation, Amazon Rainforest, Amblypygi

36

Genetic data in studies of systematics of Amazonian amphibians frequently reveal that purportedly widespread single species in reality comprise species complexes. This means that real species richness may be significantly higher than current estimates. Here we combine genetic, morphological, and bioacoustic data to assess the phylogenetic relationships and species boundaries of two Amazonian species of the Dendropsophus leucophyllatus species group: D. leucophyllatus and D. triangulum. Our results uncovered the existence of five confirmed and four unconfirmed candidate species. Among the confirmed candidate species, three have available names: Dendropsophus leucophyllatus, Dendropsophus triangulum, and Dendropsophus reticulatus, this last being removed from the synonymy of D. triangulum. A neotype of D. leucophyllatus is designated. We describe the remaining two confirmed candidate species, one from Bolivia and another from Peru. All confirmed candidate species are morphologically distinct and have much smaller geographic ranges than those previously reported for D. leucophyllatus and D. triangulum sensu lato. Dendropsophus leucophyllatus sensu stricto occurs in the Guianan region. Dendropsophus reticulatus comb. nov. corresponds to populations in the Amazon basin of Brazil, Ecuador, and Peru previously referred to as D. triangulum. Dendropsophus triangulum sensu stricto is the most widely distributed species; it occurs in Amazonian Ecuador, Peru and Brazil, reaching the state of Pará. We provide accounts for all described species including an assessment of their conservation status.

Concepts: Species, Amazon River, Brazil, South America, Amazon Basin, Andes, Peru, Amazon Rainforest

32

The El Niño-Southern Oscillation (ENSO) is the main driver of interannual climate extremes in Amazonia and other tropical regions. The current 2015/2016 EN event was expected to be as strong as the EN of the century in 1997/98, with extreme heat and drought over most of Amazonian rainforests. Here we show that this protracted EN event, combined with the regional warming trend, was associated with unprecedented warming and a larger extent of extreme drought in Amazonia compared to the earlier strong EN events in 1982/83 and 1997/98. Typical EN-like drought conditions were observed only in eastern Amazonia, whilst in western Amazonia there was an unusual wetting. We attribute this wet-dry dipole to the location of the maximum sea surface warming on the Central equatorial Pacific. The impacts of this climate extreme on the rainforest ecosystems remain to be documented and are likely to be different to previous strong EN events.

Concepts: Amazon River, Brazil, Rainforest, Tropical rainforest, Amazon Basin, Deforestation, Amazon Rainforest, Peruvian Amazon

31

Over the last 150 years, a little South American fish with alleged unsavory habits has become the stuff legends are made of. With growing visitor numbers to the Amazon basin, the question of whether the animal poses a threat to the many travelers to the region arises.

Concepts: English-language films, Amazon River, Brazil, South America, Amazon Basin, Portuguese language, Peru, Amazon Rainforest

29

Arapaima gigas, a fresh water fish found in the Amazon Basin, resist predation by piranhas through the strength and toughness of their scales, which act as natural dermal armour. Arapaima scales consist of a hard, mineralized outer shell surrounding a more ductile core. This core region is composed of aligned mineralized collagen fibrils arranged in distinct lamellae. Here we show how the Bouligand-type (twisted plywood) arrangement of collagen fibril lamellae has a key role in developing their unique protective properties, by using in situ synchrotron small-angle X-ray scattering during mechanical tensile tests to observe deformation mechanisms in the fibrils. Specifically, the Bouligand-type structure allows the lamellae to reorient in response to the loading environment; remarkably, most lamellae reorient towards the tensile axis and deform in tension through stretching/sliding mechanisms, whereas other lamellae sympathetically rotate away from the tensile axis and compress, thereby enhancing the scale’s ductility and toughness to prevent fracture.

Concepts: Continuum mechanics, Tensile strength, Amazon River, Freshwater fish, Amazon Basin, Work hardening, Deformation, Plastic deformation in solids

29

Ninety-five specimens from 13 species of lizard collected during a herpetofaunal monitoring programme of the Faxinal II power plant, municipality of Aripuanã, state of Mato Grosso, Brazil (southern Amazon region) were examined for helminths. A total of 21 helminth species (16 Nematoda, 1 Cestoda and 4 Trematoda) were recovered, with an overall prevalence of 67.37%. Seventeen new host records and seven new locality records are reported. A low number of specialists and core helminth species were found. Lizard body size was positively correlated with both the total number of helminth species and individuals. Active foragers exhibited higher helminth diversity. However, sit-and-wait foragers, especially Plica plica, had similar diversity values as active foragers and harboured more helminth species. The degree of similarity in helminth fauna was higher among closely related host species.

Concepts: Amazon River, Brazil, Amazon Basin, Portuguese language, Mato Grosso, Amazon Rainforest, Venezuela, Rondônia

28

Previous research has established the usefulness of remotely sensed vegetation index (VI) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) to characterize the spatial dynamics of agriculture in the state of Mato Grosso (MT), Brazil. With these data it has become possible to track MT agriculture, which accounts for ~85% of Brazilian Amazon soy production, across periods of several years. Annual land cover (LC) maps support investigation of the spatiotemporal dynamics of agriculture as they relate to forest cover and governance and policy efforts to lower deforestation rates. We use a unique, spatially extensive 9-year (2005-2013) ground reference dataset to classify, with approximately 80% accuracy, MODIS VI data, merging the results with carefully processed annual forest and sugarcane coverages developed by Brazil’s National Institute for Space Research to produce LC maps for MT for the 2001-2014 crop years. We apply the maps to an evaluation of forest and agricultural intensification dynamics before and after the Soy Moratorium (SoyM), a governance effort enacted in July 2006 to halt deforestation for the purpose of soy production in the Brazilian Amazon. We find the pre-SoyM deforestation rate to be more than five times the post-SoyM rate, while simultaneously observing the pre-SoyM forest-to-soy conversion rate to be more than twice the post-SoyM rate. These observations support the hypothesis that SoyM has played a role in reducing both deforestation and subsequent use for soy production. Additional analyses explore the land use tendencies of deforested areas and the conceptual framework of horizontal and vertical agricultural intensification, which distinguishes production increases attributable to cropland expansion into newly deforested areas as opposed to implementation of multi-cropping systems on existing cropland. During the 14-year study period, soy production was found to shift from predominantly single-crop systems to majority double-crop systems.

Concepts: Biodiversity, Agriculture, Soybean, Brazil, Amazon Basin, Mato Grosso, Deforestation, Amazon Rainforest

28

The dramatic range expansion of the dengue vector Aedes aegypti is associated with various anthropogenic transport activities, but little is known about the underlying mechanisms driving this geographic expansion. We longitudinally characterized infestation of different vehicle types (cars, boats, etc.) to estimate the frequency and intensity of mosquito introductions into novel locations (propagule pressure).

Concepts: Mosquito, Yellow fever, Aedes aegypti, Aedes, Dengue fever, Amazon Basin, Vehicle, Automobile