A Study Discovers That The Great Wall of China Is Guarded By A “Living Skin”

Among the most amazing man-made constructions is the Great Wall of China. Built by China’s rulers over many centuries to defend their land, the edifice has withstood the test of time and drawn millions of visitors who are in awe of the construction that dates back about 3,000 years. Its structure acquired weak spots as a result of the natural elements being compressed with the earth during construction. However, recent research discovered that they evolved a built-in defense mechanism against the ongoing threat of degradation.

The research, which was published on December 8, 2023, in Science Advances, claimed that this defense system takes the form of “living skin” composed of microscopic, rootless plants and microorganisms called biocrusts.

“We don’t typically look for biocrusts on human-built structures, but they are common throughout the world on soils of dry regions,” soil ecologist Matthew Bowker, an associate professor at Northern Arizona University and co-author of the study, told CNN.

The Great Wall’s soil surfaces are coated with biocrusts. Furthermore, the microorganisms are not only a surface layer; they are essential in strengthening the structure’s resilience to weathering and natural disintegration.

After collecting samples from a distance of more than 480 kilometers, the researchers discovered that biocrusts cover more than two-thirds of the region.

Previous research claimed that since the bacteria create acid and change the microenvironment, biocrusts pose a detrimental danger to stone buildings. When Mr. Bowker and his colleagues analyzed samples with and without the “living skin” to examine how stable and powerful the biocrust-layered samples were, they found that the biocrust-layered samples were up to three times stronger.

“They believed that the Great Wall was being destroyed by this kind of vegetation. Our findings demonstrate the opposite,” said China Agricultural University soil science professor and research co-author Bo Xiao. “Biocrusts are very widespread on the Great Wall and their existence is very beneficial to the protection of it.”

The cyanobacteria, algae, moss, fungus, and lichen that comprise the biocrusts are located on the uppermost layer of the soil. The layer’s development may take decades or perhaps longer. These biocrusts create a small ecosystem that aids in soil stabilization, improves water retention, and controls the fixation of nitrogen and carbon.