Impactos ecológicos e ecotoxicológicos das culturas de cana-de-açúcar nas comunidades de girinos anfíbios
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Data
2019-04-26
Autores
Sánchez-Domene, David
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O Estado de São Paulo é responsável pela produção da metade da cana-de-açúcar no Brasil, e segue crescendo, sendo esse cultivo um dos principais responsáveis pelo desmatamento no interior do estado. A atual expansão da cana-de-açúcar está ocorrendo principalmente sob áreas de cultivos anuais e pastagens de pecuária extensiva. Embora possa parecer positivo, essa conversão de pastagens supõe um grande impacto sobre as poças de água construídas como bebedouros para o gado, as quais abrangem altas proporções de biodiversidade a sua vez. Nesse cenário, os anfíbios são especialmente vulneráveis, uma vez que a grande maioria das espécies de anuros, registrados no interior do estado, se reproduz nestas poças que estão sendo transformadas ou mesmo desaparecendo. Além disso, o cultivo intensivo de cana-de-açúcar exige o uso de agrotóxicos que devido as fortes precipitações sazonais provocam escoamento superficial a estes leitos aquáticos e sua subsequente contaminação por misturas complexas de pesticidas. Nesta dissertação de doutorado são apresentados os resultados de um estudo sobre os impactos ecológicos e ecotoxicológicos em girinos de diferentes espécies de anuros que habitam poças temporárias anexas aos cultivos de cana-de-açúcar. O estudo foi realizado na área agrícola circundante da cidade de São José do Rio Preto, uma das principais áreas de produção de cana-de-açúcar no noroeste paulista. A vegetação nativa dessa região tem sido continuamente desmatada desde o século XIX, e nas últimas décadas tem experimentado uma intensa expansão do cultivo de cana-de-açúcar, substituindo principalmente pastagens, o que torna essa região um local idôneo para pesquisa da anurofauna, a qual tem sido extensivamente estudada desde meados dos anos 60. Para compreender os impactos ecológicos e ecotoxicológicos nos girinos que habitam as poças temporais anexas aos cultivos de cana-de-açúcar, esta dissertação está formada por quatro capítulos nos quais são avaliados i) os impactos do cultivo da cana-de-açúcar sobre a estrutura das comunidades de anuros associadas a poças temporárias por meio do estudo dos efeitos das características locais das poças, da paisagem entorno a elas e da contaminação por pesticidas, ii) as malformações oculares encontradas em girinos coletados durante as amostragens de campo, iii) a confiabilidade do teste de desempenho de natação de escape como ferramenta para a detecção de comprometimento da mobilidade em organismos aquáticos expostos a pesticidas, e iv) os efeitos nas comunidades de água doce das misturas de pesticidas em um experimento microcosmos. Os resultados desses estudos vão desde a confirmação da importância das poças para a conservação de anfíbios, até a detecção de contaminação generalizada na região de São José do Rio Preto, bem como a apresentação dos primeiros casos de malformações anfíbias em paisagens agrícolas no Brasil, e a primeira linha de base de malformações para anfíbios na América do Sul.
São Paulo state cultivates half of the sugarcane in Brazil, being this culture among the main responsible for deforestation in the inland of the state. Current expansion of sugarcane is taking place mostly over annual croplands and extensive cattle ranching pastures. Although it may seem positive, this pasture conversion supposes a major impact on cattle ponds which support high proportions of biodiversity. In this scenario, amphibian populations are especially vulnerable since the vast majority of the anurans registered in the inland of the state breed in cattle ponds which are been transformed or even disappearing. In addition, intensive sugarcane culture demands the usage of pesticides which can enter ponds when heavy precipitation events cause surface run-off. Consequently, complex mixtures of pesticides occur in ponds near to cultures. In this doctoral dissertation are presented the results of a study of the ecological and ecotoxicological impacts on tadpoles of anurans species inhabiting temporary breeding ponds annex to sugarcane cultures. The study was conducted in the surrounding sugarcane-dominated agricultural area of the city of São José do Rio Preto, which stands out as an appropriate place for the research purpose, since it is part of São José do Rio Preto macro region, in the northwestern of São Paulo state, one of the major sugarcane production areas in Brazil, its native vegetation has been intensely deforested since the 19th century, in the last decades has experienced one of the greatest sugarcane expansions, mostly replacing cattle pastures, and its anurofauna has been extensively studied since mid-1960s. The dissertation includes four chapters in which are assessed i) the impacts of sugarcane cultivation on the anuran communities structure associated to temporary breeding ponds by assessing the effects of ponds characteristics, landscape and pesticides contamination, ii) eye malformation found in tadpoles collected during field samplings, iii) the reliability of the escape swimming performance test as a tool for the detection of motility impairment in aquatic organisms exposed to a pesticides, and iv) the effects on freshwater communities of pesticides mixtures in an outdoor microcosms experiment. The findings from these studies range from the confirmation of the importance of cattle ponds for amphibian conservation to the detection of widespread contamination in São José de Rio Preto region, as well as the introduction of the first report of amphibian malformations in agricultural landscapes in Brazil, as well as first malformation baseline for amphibians in South America.
São Paulo state cultivates half of the sugarcane in Brazil, being this culture among the main responsible for deforestation in the inland of the state. Current expansion of sugarcane is taking place mostly over annual croplands and extensive cattle ranching pastures. Although it may seem positive, this pasture conversion supposes a major impact on cattle ponds which support high proportions of biodiversity. In this scenario, amphibian populations are especially vulnerable since the vast majority of the anurans registered in the inland of the state breed in cattle ponds which are been transformed or even disappearing. In addition, intensive sugarcane culture demands the usage of pesticides which can enter ponds when heavy precipitation events cause surface run-off. Consequently, complex mixtures of pesticides occur in ponds near to cultures. In this doctoral dissertation are presented the results of a study of the ecological and ecotoxicological impacts on tadpoles of anurans species inhabiting temporary breeding ponds annex to sugarcane cultures. The study was conducted in the surrounding sugarcane-dominated agricultural area of the city of São José do Rio Preto, which stands out as an appropriate place for the research purpose, since it is part of São José do Rio Preto macro region, in the northwestern of São Paulo state, one of the major sugarcane production areas in Brazil, its native vegetation has been intensely deforested since the 19th century, in the last decades has experienced one of the greatest sugarcane expansions, mostly replacing cattle pastures, and its anurofauna has been extensively studied since mid-1960s. The dissertation includes four chapters in which are assessed i) the impacts of sugarcane cultivation on the anuran communities structure associated to temporary breeding ponds by assessing the effects of ponds characteristics, landscape and pesticides contamination, ii) eye malformation found in tadpoles collected during field samplings, iii) the reliability of the escape swimming performance test as a tool for the detection of motility impairment in aquatic organisms exposed to a pesticides, and iv) the effects on freshwater communities of pesticides mixtures in an outdoor microcosms experiment. The findings from these studies range from the confirmation of the importance of cattle ponds for amphibian conservation to the detection of widespread contamination in São José de Rio Preto region, as well as the introduction of the first report of amphibian malformations in agricultural landscapes in Brazil, as well as first malformation baseline for amphibians in South America.
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Palavras-chave
Anfíbios, Cana-de-açúcar, Pesticidas, Mudança do uso do solo, Amphibians, Sugarcane, Pesticides, Land-use-change