Variabilidade da Área de Cultivo do Algodão Herbáceo em Sistema de Sequeiro no Nordeste do Brasil Segundo Cenários de Mudanças Climáticas (Variability in Area of Upland Cotton in Rainfed System in Northeastern Brazil the Second Climate Change Scenarios)

Este estudo avalia os impactos das alteracoes climaticas sobre o zoneamento agricola de risco climatico do algodoeiro herbaceo (Gossypium hirsutum L. latifolium Hutch) cultivado na regiao Nordeste do Brasil. O modelo de balanco hidrico, combinado com tecnicas de geoprocessamento (SIG), foi utilizado para identificar as areas da regiao de estudo onde a cultura sofrera restricoes de rendimento devido as mudancas climaticas. Os dados utilizados no estudo foram as series historicas de precipitacao pluvial com no minimo 30 anos de dados diarios, coeficientes de cultura, evapotranspiracao potencial e a duracao do ciclo da cultura. Os cenarios denominados de A, B e C sao correspondentes, respectivamente, aos aumentos de temperatura do ar de 1,5; 3 e 5 oC. Esses cenarios de aumento de temperatura do ar foram associados com as alteracoes na precipitacao de ±10; ±25 e ±40%, correspondentes aos eventos de El Nino (desvios negativos) e de La Nina (desvios positivos) na simulacao da epoca de semeadura da cultura. Foi adotado como criterio de corte para o Indice de Satisfacao das Necessidades de Agua para a cultura (ISNA), definido como a relacao entre a evapotranspiracao real e a evapotranspiracao maxima (ETr/ETm), o valor 0,55. Os resultados obtidos sugerem que as mudancas climaticas levam a reducao das areas agricultaveis favoraveis ao cultivo com o algodoeiro herbaceo na regiao Nordeste do Brasil.  Palavras - chave: Precipitacao pluvial, Balanco hidrico, Mudancas climaticas.  Variability in Area of Upland Cotton in Rainfed System in Northeastern Brazil the Second Climate Change Scenarios ABSTRACT This study assesses the impacts of climate change on the agricultural zoning of climatic risk in cotton (Gossypium hirsutum L. latifolium Hutch) grown in northeastern region of Brazil. The water balance model, combined with geospatial technologies (GIS), was used to identify areas of the study area where the crop will suffer yield restrictions due to climate change. The data used were the time series in rainfall at least 30 years of daily data, crop coefficients, potential evapotranspiration and duration of the crop cycle. The scenarios referred here as A, B and C are corresponding to the increases in air temperature of 1.5, 3 and 5 o C, respectively. These scenarios of increase in air temperature were associated with changes in precipitation ± 10, ± 25 and ± 40%, which are associated to the El Nino events (negative deviations) and La Nina (positive deviations) in the simulation of sowing crop. It was adopted as baseline for the Index of Satisfaction of Water Requirements for culture (ISNA), defined as the ratio between actual evapotranspiration and maximum evapotranspiration (ETr/ETm), the value 0.55. The results suggest that climate change leads to the reduction in agricultural areas of cotton crop growth in northeastern region of Brazil. Keywords: Rainfall, Water balance model, Climatic change