Land-Use and Bakin Birji Pond Dynamics in Relation to Climate Variability and Malaria Seasonality in Zinder Region, Niger

Abstract

This study examined long-term land-use and Bakin Birji pond dynamics together with the seasonal pattern of confirmed malaria cases in a semi-arid setting of Zinder Region, Niger. Land-use maps were prepared from Landsat imagery for 1993, 2008 and 2023; climatic data for 1993-2022 were obtained from NASA POWER; and monthly rapid-diagnostic-test-confirmed malaria counts for 2019-2022 were obtained from the Bakin Birji Integrated Health Centre. Pearson and Spearman correlations were used as exploratory measures of association between monthly climatic variables and malaria counts. Between 1993 and 2023, pond area increased from 1.22 to 3.97 ha (+225.4%), vegetated area decreased from 1,870.78 to 958.87 ha (-48.7%), and built-up area increased from 89.63 to 347.87 ha (+288.1%). Malaria showed pronounced seasonality, with the highest mean monthly counts in September (1,041) and October (990), following the main rainfall peak in August. Rainfall and malaria showed moderate positive correlations (Spearman rho = 0.55, p = .064; Pearson r = 0.47, p = .123), while specific humidity showed a moderate Spearman association (rho = 0.54, p = .070) and a stronger Pearson association (r = 0.75, p = .005). The temperature association was inverse but method-dependent (Spearman rho = -0.71, p = .010; Pearson r = -0.32, p = .311). These results document substantial hydro-landscape change and wet-season malaria seasonality, but the different temporal resolutions of the pond and malaria datasets do not permit a direct causal attribution of malaria patterns to pond expansion. Finer-resolution environmental monitoring and longer, population-standardised malaria time series are needed to test lagged and causal relationships.