In towns and cities a range of materials are used to build houses, public buildings and transport infrastructure. In historic cities the heritage value of stone buildings and monuments is significant, but these are vulnerable to the same weathering and erosion processes as natural rock. This is also true for materials such as concrete and brick.
Biogeomorphologists have an interest in the roles of microorganisms, animals and plants on built structures. This includes how they actively deteriorate materials, by increasing the speed they break down and discolour. Organisms can also increase or decrease the rate of other important weathering processes involving moisture, salts and pollution. The influence of material properties and engineering designs on the kinds of organisms that grow on structures is also important for managing biodiversity and heritage conservation in the built environment.
Ivy is a very common plant in urban environments. It can often be found growing in parklands, graveyards and on buildings. It is particularly common on historic structures, including ruined sites, where it can completely cover vertical surfaces. Climbing plants like ivy have also been used as ornamental wall coverings for hundreds of years, and they provide an important habitat for a whole range of wildlife.
Ivy can cause damage to buildings especially old structures built from vulnerable stone, but may also provide some protection. This has been the subject of research at the University of Oxford funded by English Heritage. This work has shown how ivy canopies can protect stone by keeping it cool in summer and warm in winter, and by shielding structures from wind, rain and urban pollution. Where ivy is growing on structures in a poor condition, the plant can exploit existing defects and make the situation worse. Careful management is therefore needed.