Abstract
The Carajás National Forest contains some of the largest iron ore deposits in the world. The majority of the minerals are found below a plant community known as Savana Metalófila, or “Canga”, which represents only 3% of the landscape within the Carajás National Forest (CNF). The aim of our study was to understand the diversity of community of non-volant small mammals in the two predominant vegetation types: Ombrophilous Forest and Canga, and to examine how mining impacts these communities. Sampling was conducted from January 2010 to August 2011 in 11 sampling sites divided by the total area of Canga and 12 sampling sites in the forest, totalizing 23 sites. Of these, 12 sites (Canga and Forest) were considered impacted areas located close to the mine (<< 900 meters) and 11 sites (Canga and Forest), serving as controls, which were at least 7,000 meters from the mine. We recorded 28 species, 11 from the Order Didelphimorphia and 17 from the Order Rodentia. The two forest types shared 68.42% of the species found in the CNF. A gradient analysis (Non-metric multidimensional scaling) revealed that the first axis clearly separated the non-flying small mammal communities by vegetation type. Occupancy models showed that the detectability of species was affected by the distance from the mining activities. Of all the small mammals analyzed, 10 species were positively affected by the distance from mining in areas impacted (e.g. more likely to be detected farther from mining areas) and detectability was lower in impacted areas. However, three species were negatively affected by the distance from mining, with higher detectability in the impacted areas, and seven species showed no effect of their proximity to mining operations. To date, there are no studies in Brazil about the impact of mining on mammals or other vertebrates. This study reveals that the effect of mining may go beyond the forest destruction caused by the opening of the mining pits, but also may negatively affect sensitive wildlife species.
Highlights
The Amazonian Biome, with its wide variety of habitats, has the highest diversity of non-volant small mammals (Orders Didelphimorphia and Rodentia) in the world, with 83 endemic species of marsupials and rodents
The iron ore extracted from the Serra dos Carajas is found under a vegetation type known as Savana Metalofila or “Canga”, which covers about 3% of the landscape, and the rest of the Carajas National Forest (CNF) is dominated by Ombrophilous forests [3]
Our study attempts to verify the community structure of non-volant small mammals in the two primary vegetation types of the CNF (e.g. Ombrophilous Forest and Canga), and to assess the impact of mining on each species through occupancy and detectability models using the distance from the mine as representative of the impact. Based on this objective we developed the following hypotheses: 1) the diversity of the small mammal community is different between the two sampled vegetation types, due to differences in the complexity of each vegetation type, and species richness will be higher in Ombrophilous Forest areas; and 2) capture rates are lower in areas closest to the mine, especially in the Ombrophilous Forest because this vegetation type presents more complex microhabitats and will be more affected
Summary
The Amazonian Biome, with its wide variety of habitats, has the highest diversity of non-volant small mammals (Orders Didelphimorphia and Rodentia) in the world, with 83 endemic species of marsupials and rodents. Over the last 20 years, 92 species of mammals have been described worldwide, and 74% are exclusive to Brazil, mostly from the Brazilian Amazon [1]. With the discovery and development of natural resources in the last 50 years, deforestation has intensified in Amazonia. The establishment of Carajas Project has brought mining activities to the region [2] and the Serra dos Carajas, in eastern Amazonia, Brazil, holds the largest iron ore deposits in the world [2]. The iron ore extracted from the Serra dos Carajas (i.e. the Carajas National Forest, “CNF”) is found under a vegetation type known as Savana Metalofila or “Canga”, which covers about 3% of the landscape, and the rest of the CNF is dominated by Ombrophilous forests [3]
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