Agriculture-livestock production forecasts and reproduction of Podocnemis expansa in the environs of the Ilha do Bananal in Tocantins State

Abstract

Agriculture and livestock forecasts for the municipalities of Caseara, Cristalândia, Formoso do Araguaia, Lagoa da Confusão, Marianópolis and Pium are analyzed with regard to the number of females of the species P. expansa nidifying on the sandbanks of the river Javaés during the execution period of the Projeto Quelônios da Amazônia (PQA), between 1985 and 2010. Agriculture and livestock production data were analyzed for the 1990-2015 period taking into consideration the number of cattle heads and planted area with temporary and permanent culture for all the municipalities concerned. Data were analyzed and forecasted by the integrated self-regressive temporal series of Box Jenkins´s movable media. Agriculture and livestock production data revealed that, in 1990, 73.5% of the area was covered by savanna, with 62.1% in 2015, or rather, an 11.4% decrease, caused by increase in agriculture and livestock activities. In the case of the number of nidifying P. expansa females, data series was unstable, with short periods in growth and decrease, with no possible standard of variables with agriculture and livestock production on the banks of the river Javaés. Results demonstrate that other variables exist which ‘apparently’ cause smaller impacts on the environment, such as climate variations which have a bigger effect on the population of nidifying females on the banks of the river Javaés than the agriculture-livestock expansion in the region.