Research shows that the loess plain, traversed by the Yellow River and covering six provinces and one territory in northern China, was once a region rich in forests and vegetation, and that the river, as described in the ancient Shih ching, or Book of Songs, was once "clear and rippling."
根據大陸歷史地理學家史念海的考證，千百年前的黃河流域「草被豐藏，松柏成林」，正如「詩經」魏風伐壇篇所說的「河水清且漣漪」。黃河流經的黃土高原，跨陝、甘、寧、青、晉、豫和內蒙古七個省區，那時處處森林廣被。