The problem of the plateau
The Loess Plateau of north-central China covers 640,000 square kilometers and is one of the most erosion-prone regions on Earth. The soil here is loess, a silty, loosely-packed sediment deposited by wind over millennia. This material is extremely vulnerable to erosion by water and wind. Historically, intense farming and deforestation stripped the plateau of its protective vegetation, leading to catastrophic soil loss. At its peak, some areas saw erosion rates as high as 15,000 tons per square kilometer per year.
This immense quantity of eroded soil has a very famous destination: the Yellow River. The river, which flows through the plateau, gets its characteristic color and its name from the vast amount of loess it carries. In the mid-20th century, the river transported an estimated 1.6 billion tons of sediment annually. This sediment raises the riverbed downstream, causing devastating floods that have marked Chinese history for centuries. To understand and combat this process, scientists needed a living laboratory.
A decades-long experiment in this eroding landscape near Guyuan city in the Liupanshan mountain region, researchers established a series of outdoor experiments.%%CITE_6%%%%CITE_7%% The Guyuan Experimental Station on Ecology, run by the Chinese Academy of Sciences, features numerous runoff plots.%%CITE_6%%%%CITE_7%%%%CITE_8%% These are carefully monitored, rectangular sections of land built on slopes. Each plot is designed to measure exactly how much soil and water runs off its surface during rainfall.
By maintaining different conditions on each plot—from tilled earth to various types of grasses, shrubs, and trees—scientists can precisely quantify the effectiveness of different vegetation covers. For decades, they have collected data on rainfall intensity, runoff volume, and sediment yield. The results provide hard numbers on how well different plant species anchor the soil. This data showed that human activities, particularly land management, were the main drivers of historical erosion changes.
The findings from these plots and similar research stations across the plateau directly informed one of the most ambitious ecological restoration projects in history: the "Grain for Green" program. Launched in 1999, this nationwide initiative paid farmers to convert sloped cropland back into forest and grassland. The program has been a major factor in reducing erosion, with human-led conservation efforts accounting for up to a 98% reduction in sediment load in some areas. As a result, the sediment entering the Yellow River from the Loess Plateau has fallen to less than a quarter of what it was before 1980.