Much of the Great Wall endures because tiny guardians — cyanobacteria and algae — cushion it against the pace of erosion. A study conducted by researchers at the China Agricultural University in Beijing and published in Science Developments examined how microbial life contributes to the wall’s resilience. The researchers focused on the wall’s textures, materials, and micro-environments to understand how microbes interact with soil and stone to influence durability over centuries.
To assess the wall’s structural integrity, the team gathered samples from eight representative sites along the wall that reflect its long construction history, spanning from early sections to later improvements during the Ming Dynasty. Analyses revealed that about two thirds of the samples contained thin microbe bioshells, delicate layers formed by microbial communities. In areas where these bioshells were present, the wall exhibited noticeably greater strength, with mossy sections showing particularly robust performance. The scientists explained that cyanobacteria and other microbes secrete sticky, binding substances that adhere tightly to soil particles, effectively creating a cement-like matrix that helps bind the wall materials together and resist erosion.
The Great Wall of China extends well over 21,000 kilometers and was constructed over many generations, with foundational work beginning long before the Ming era. During its construction, builders often used mixes of organic materials, including soil and rock, to unify and stabilize the structure. This material environment also supported the growth of cyanobacteria, algae, and lichens, organisms that feed on sunlight and minerals while contributing to the micro-scale chemistry of the wall’s surface. Over time, these organisms can form protective films that reduce weathering and micro-cracking, essentially acting as natural sealants that help preserve segments exposed to wind, sun, and rain. This biofilm layer can also influence moisture retention and micro-topography, factors that play a key role in the wall’s long-term preservation and ongoing maintenance needs.
In recent years, researchers have continued to explore how microbial life interacts with ancient stone monuments. The findings related to the Great Wall echo lessons from other historic structures where biofilms and microbial mats contribute to both deterioration and preservation. Understanding these processes offers new avenues for conservation—balancing the control of harmful microbial activity with the appreciation that some biofilms can act as protective shields against harsher weathering. By studying microbial communities at multiple wall sites, scientists are identifying the precise conditions under which these organisms help, rather than hurt, the monument’s endurance. In turn, this knowledge supports more informed preservation strategies that respect the wall’s historical material choices while addressing modern environmental challenges.