Stone-eating bugs present monumental challenge

World-famous buildings in London once ravaged by acid rain are facing a new threat from bacteria and insects, flourishing in the capital's cleaner air, that eat into stone and wood.

World-famous buildings in London once ravaged by acid rain are facing a new threat from bacteria and insects, flourishing in the capital's cleaner air, that eat into stone and wood.

The microbes and airborne plants pose a serious danger to landmarks such as the Houses of Parliament and Somerset House, while climate change will bring torrential rain that will seriously damage buildings across the capital.

A €1.2m (£805,000) study into the threats that climate change poses to Europe's heritage warnsthat the rising output of nitrogen oxides from cars, together with cuts in sulphur output from power stations burning coal, has created the ideal conditions for bacteria and lichen to settle and grow on the nation's best-known monuments.

Rising vehicle pollution is doubly to blame as it is also driving climate change by putting more carbon dioxide into the atmosphere. And the changing pattern of rainfall towards intense downpours, will create perfect conditions to strip plaster from the inside of ancient buildings and promote mould.

Peter Brimblecombe, professor of atmospheric chemistry at the University of East Anglia, said: "Micro-organisms will make use of minerals in the stone to contribute to their own growth. This kind of damage is already happening in London, and with the changing climate the potential is that it will lead to faster degradation of the surfaces of all kinds of objects." Although the bacteria and fungi eat only the surface of any monument, the type of rock usually chosen for such objects, such as marble, is very liable to being absorbed. "They only eat a millimetre into the stone, but that disintegrates the microcrystals that are cemented together to make the stone," said Professor Brimblecombe. "That leads to corrosion rates of some millimetres per year."

The threat from the bacteria and fungi is all the more ironic because they could not survive in acid rain. "Pretty much everything in acid rain was phyto-toxic - it killed bacterial growth," he said. The study's authors warn that climate changecould damage many landmarks including Hadrian's Wall, the Temples of Agrigento in Sicily and the Charles bridge in Prague.

Dr Cristina Sabbioni of the Institute for Atmospheric Sciences in Bologna, who is leading the project, said: "Sandstorms caused by desertification could lead to the erosion of the ancient temples and historic palaces of southern Italy, while flooding in northern Europe could create a hazard to structures built in wood or containing clay binders, materials that deteriorate on contact with water".

The Thames in London poses a particular threat, with rising sea levels and the greater chance of flash-flooding caused by downpours, said Professor May Cassar at the Centre for Sustainable Heritage at University College London: "That could flood huge areas of the Houses of Parliament, as well as other important buildings."