A biological community protects the Great Wall of China – 2024-04-04 16:30:54

/View.info/ New research reveals that large parts of the Great Wall of China, which is a UNESCO World Heritage Site, are protected by a biological community. It was discovered on the surface of the ancient defensive walls.

According to the study, which was published Saturday in the journal Science Advances, biological soil crusts, or biocrusts, consisting of photosynthetic bacteria, mosses and lichens, help increase the stability of ancient structures and prevent erosion caused by rain and wind.

The Great Wall of China consists of many interconnected walls, some dating back 2,000 years. The total length of the wall is over 21,000 kilometers. The most recognizable parts were built during the Ming Dynasty between 1368 and 1644.

Many sections of the wall, especially those in drier areas, are built with rammed earth, in which soil and gravel are compacted into dense clay mixtures.

Some workers involved in the conservation of the wall believe that the natural vegetation can speed up the weathering process. But the results of the new study found the opposite conclusion.

Researchers from the Chinese Academy of Sciences and China Agricultural University examined the structural stability and erodibility of rammed earth samples that were taken from eight sections of the Great Wall from the Ming Dynasty era.

They found that biocrusts covered 67 percent of the areas studied. It also became clear that cyanobacteria, a group of bacteria containing a blue photosynthetic pigment, dominated biocrusts in arid regions, while Pottiaceae mosses thrived in wetter, semiarid climates.

Overall, biocrusts, especially those dominated by mosses, increased the mechanical strength of the wall and the stability of the soil by 37 to 178 percent compared to bare rammed earth, said Xiao Bo, who authored the study.

Researchers are also working to study the effects of wind, rain and temperature fluctuations. “Biocrusts serve as stabilizers, sacrificial layers and drainage roofs, combining the protective functions of several conventional measures into one ecological approach,” adds Xiao.