Graduate Thesis Or Dissertation
 

Rapid endangered species assessment : a novel approach to improve extinction risk assessments in poorly known species

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  • The number of endangered species is rapidly increasing while paucity of adequate information and resources delays establishment of conservation actions. The IUCN’s listing system is insufficient to determine conservation priorities and many species lack information even to be evaluated (i.e., “data deficient”). Here I proposed and tested the Rapid Endangered Species Assessment approach, combining methods including distribution modeling, landscape/habitat availability analysis and an evaluation of population spatial structure to improve information about species of concern and make future extinction risk assessments more attainable. I used the Pfrimer’s Parakeet (Pyrrhura pfrimeri) an endemic Brazilian species, as a case study. I modeled and validated the potential distribution of the species, known to occur in association with the tropical dry forests in central Brazil, using the Maxent method. The model predicted potential occurrence in three regions in central Brazil. Field surveys used to validate model found the species at 17 sites, all located in the dry forests of the Paranã River Basin. Modeling results set boundaries for the analysis of loss and fragmentation of the species’ habitat. Satellite imagery and remote sensing techniques were used to estimate deforestation trends over a large spatiotemporal scale (31 years). Results indicated a 66.3% decrease in forest extent, average annual deforestation rate of 2.1% and significant increase in fragmentation, suggesting that these forests may disappear in less than 20 years if current deforestation rates persist. The habitat availability analysis set boundaries for the investigation of spatial arrangement of local populations of Pfrimer’s Parakeets, which was carried out by collecting information on abundance, densities estimates, species home range, and habitat use. Twenty individuals were monitored with radio transmitters and home range estimates averaged between 195.7 ha (fixed kernel) and 261.8 ha (minimum convex polygons). Habitat use was estimated with behavioral observations of birds flying through a mosaic of forests and pastures. I found no evidence that the species used open areas farther than 300m from the forest edge. Systematic line transects and observations of parakeets per time effort produced estimates of population densities at 11.7 individuals/km2; indicating strong variation in abundance indices among areas, suggesting a population decline. The Rapid Endangered Species Assessment represents a broad and integrative approach carried out over a short term and was successfully used to produce relevant data about a poorly known species. Thus, I propose the use of this approach as a minimally ideal yet scientifically viable method to generate information for extinction risk assessment of species.
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