Disentangling the effects of hydro-climatic factors and land use intensification on wetland vegetation dynamics in the Lower Delta of the Paraná River

Abstract

The non-insular portion of the Lower Delta of the Paraná River is part of the largest mosaic of wetlands in Argentina. However, it is being altered by intensification of cattle grazing and the increasingly rapid implementation of water management infrastructure. In this context, studying the relationship between hydro-climatic variables and vegetation growth is urgent to ensure sound management and conservation. To overcome the limitation of high cloud cover in the area which has hampered the construction of regularly spaced high-resolution time series, we implemented the recently developed spatio-temporal vegetation index image fusion model (STVIFM). In order to understand the relationship between vegetation growth and hydro-climatic factors, we performed pixel-wise correlation analyses between the newly synthesized monthly (30m) NDVI time series and hydro-climatic variables. Then, we tested whether water control infrastructure alters these relationships. Based on the accurate performance of STVIFM, we provide quantitative and spatially accurate evidence on the positive, complementary and heterogeneous relationships between vegetation growth, temperature, rainfall and the flood pulse. Our results show that water management infrastructure decouples certain areas from its natural hydrological regime, decreasing water availability and altering vegetation growth dynamics. In this context, urgent action is needed aimed towards implementing land planning measures that consider the natural variability and hydrologic regime of the system while balancing production and conservation.