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Title: The costs of evaluating species densities and composition of snakes to assess development impacts in Amazonia
Authors: Fraga, Rafael de
Stow, Adam J.
Magnusson, William Ernest
Lima, Albertina Pimental
Keywords: Controlled Study
Economic Evaluation
Environmental Impact Assessment
Environmental Monitoring
Population Density
Sample Size
Species Composition
Species Difference
Species Identification
Tropical Rain Forest
Costs And Cost Analysis
Population Density
Issue Date: 2014
metadata.dc.publisher.journal: PLoS ONE
metadata.dc.relation.ispartof: Volume 9, Número 8
Abstract: Studies leading to decision-making for environmental licensing often fail to provide accurate estimates of diversity. Measures of snake diversity are regularly obtained to assess development impacts in the rainforests of the Amazon Basin, but this taxonomic group may be subject to poor detection probabilities. Recently, the Brazilian government tried to standardize sampling designs by the implementation of a system (RAPELD) to quantify biological diversity using spatiallystandardized sampling units. Consistency in sampling design allows the detection probabilities to be compared among taxa, and sampling effort and associated cost to be evaluated. The cost effectiveness of detecting snakes has received no attention in Amazonia. Here we tested the effects of reducing sampling effort on estimates of species densities and assemblage composition. We identified snakes in seven plot systems, each standardised with 14 plots. The 250 m long centre line of each plot followed an altitudinal contour. Surveys were repeated four times in each plot and detection probabilities were estimated for the 41 species encountered. Reducing the number of observations, or the size of the sampling modules, caused significant loss of information on species densities and local patterns of variation in assemblage composition. We estimated the cost to find a snake as $ 120 U.S., but general linear models indicated the possibility of identifying differences in assemblage composition for half the overall survey costs. Decisions to reduce sampling effort depend on the importance of lost information to target-issues, and may not be the preferred option if there is the potential for identifying individual snake species requiring specific conservation actions. However, in most studies of human disturbance on species assemblages, it is likely to be more cost-effective to focus on other groups of organisms with higher detection probabilities. © 2014 Fraga et al.
metadata.dc.identifier.doi: 10.1371/journal.pone.0105453
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