The decay of historical buildings as they age is a universal phenomenon from which no civilization and no country is exempt. Such decay is particularly serious in regions suffering from severe climatic conditions. The rate of deterioration has been considerably increased in recent years by air pollution in urban and industrial concentrations. Atmospheric pollution lies at the origin of a whole chemical and bacteriological or fungal attack on stone which defaces buildings and makes stonework pliable and brittle. Such pollution also disfigures historic buildings with layers of ash and soot, which, removed by abrasive action, cause further damage to the surface.
Monuments may also be deliberately destroyed because of ignorance and lack of appreciation of the value of the heritage, particularly as a result of changes of architectural fashion and concepts of beauty. In some cases the population may have a latent antipathy for the architectural witnesses of civilizations or peoples whose contributions are rejected, disputed, or simply undervalued. This rejection also occurs when a population has changed its faith to a form which favours a completely different architectural emphasis. Wrong use or reuse is equally an important cause of the deterioration of monuments.
Finally, the historically recent processes of urbanization, industrialization and increases in leisure make much greater demand on space while at the same time leading to the abandoning of rural zones and thus of their heritage. Monuments and sites consequently come under heavy pressure. Governments may try to relieve pressure on traditional tourist attractions by encouraging more visitors to less known or remote sites.
The 18th century Gresham building in Brussels Place Royale is affected by fungi and could collapse. Treating the problem is not easy: while the fungi damage the stone on the inside, they can also form a protective coating on the outside that protects the stone from the weather.