Houspanossian Javier, Giménez Raul, Whitworth-Hulse Juan I, Nosetto Marcelo D, Tych Wlodek, Atkinson Peter M, Rufino Mariana C, Jobbágy Esteban G
Grupo de Estudios Ambientales, CONICET, San Luis, Argentina.
Departamento de Geología, National University of San Luis, San Luis, Argentina.
Science. 2023 Jun 30;380(6652):1344-1348. doi: 10.1126/science.add5462. Epub 2023 Jun 29.
Regional effects of farming on hydrology are associated mostly with irrigation. In this work, we show how rainfed agriculture can also leave large-scale imprints. The extent and speed of farming expansion across the South American plains over the past four decades provide an unprecedented case of the effects of rainfed farming on hydrology. Remote sensing analysis shows that as annual crops replaced native vegetation and pastures, floods gradually doubled their coverage, increasing their sensitivity to precipitation. Groundwater shifted from deep (12 to 6 meters) to shallow (4 to 0 meters) states, reducing drawdown levels. Field studies and simulations suggest that declining rooting depths and evapotranspiration in croplands are the causes of this hydrological transformation. These findings show the escalating flooding risks associated with rainfed agriculture expansion at subcontinental and decadal scales.
农业对水文的区域影响大多与灌溉有关。在这项研究中，我们展示了雨养农业如何也能留下大规模的印记。过去四十年来，南美洲平原上农业扩张的范围和速度为雨养农业对水文的影响提供了一个前所未有的案例。遥感分析表明，随着一年生作物取代了原生植被和牧场，洪水覆盖面积逐渐增加了一倍，使其对降水的敏感度提高。地下水从深层（12至6米）转变为浅层（4至0米）状态，降低了水位下降幅度。实地研究和模拟表明，农田根系深度和蒸散量的下降是这种水文变化的原因。这些发现表明，在次大陆和十年尺度上，与雨养农业扩张相关的洪水风险正在不断升级。
