Scientists discover why the Great Wall of China has remained so well preserved for over 2,000 years
By: Joseph Shavit
The Great Wall of China, a symbol of ancient civilization, stretches across the northern borders, standing as a testament to over two millennia of history.
The Great Wall of China, a symbol of ancient civilization, stretches across the northern borders, standing as a testament to over two millennia of history. Despite its grandeur, what remains today is only a fraction of its former self, as time and natural forces have taken their toll on the structure.
However, a recent discovery reveals that nature itself might be playing a crucial role in preserving this historical wonder. Thin layers of bacteria, moss, lichen, and other organisms, known as biocrusts, have been found to protect sections of the Great Wall, shielding it from wind, rain, and other corrosive elements.
A study published in Science Advances highlights the significant role these “living skins” play in conserving this ancient architectural marvel. With advances in technology and research, scientists are now exploring the potential of cultivating new biocrusts to prevent further degradation of the Wall.
Nichole Barger, an ecologist at the Nature Conservancy, praised the study as “innovative and creative,” noting that the protective effects of biocrusts have gained increasing recognition in recent years. These biological layers are well-known for stabilizing dryland ecosystems and preventing soil erosion.
While the more famous sections of the Great Wall are constructed from stone or brick, other parts were built using compacted soil, or rammed earth. Over time, this material deteriorates due to various factors like rainwater infiltration, wind erosion, salt crystal formation, and temperature fluctuations.
Yet, the same compacted soils can also host biocrusts, which cover about 12% of the Earth’s land surface, particularly in arid regions like northern China. These biocrusts vary in form, ranging from thin bacterial networks a few millimeters thick to thicker layers of moss and lichen several centimeters high.
Soil scientist Bo Xiao from the China Agricultural University, along with his colleagues, conducted a study to investigate the role of biocrusts in preserving the Great Wall. Their research revealed that biocrusts, primarily composed of moss or cyanobacteria, covered more than two-thirds of the Wall’s surface in the areas they examined. By comparing the physical properties of biocrust-covered rammed earth with those of bare, biocrust-free soil, they made a significant discovery.
