The growth of Lichen is one of the first stages in erosion. It gets into the cracks of masonry and deteriorates. I know this is a very slow process but an important one at that. Nowadays stone and concrete cladding is just that - skin. It has no structural bearing. I'm thinking that for most buildings, panels could be replaced if they're ever in danger of crumbling, but I'd at least like to hear a little science on this. And in New York, where there are plenty of structural masonry buildings still (each potentially becoming heritage status), this could be an even bigger problem. Wow. I feel like a major buzzkill now.
I would guess that it takes a very long time. Or, if it didn't maybe lichen-friendly materials could be used. Oh, bummer: When growing on mineral surfaces, some lichens slowly decompose their substrate by chemically degrading and physically disrupting the minerals, contributing to the process of weathering by which rocks are gradually turned into soil. While this contribution to weathering is usually benign, it can cause problems for artificial stone structures. For example, there is an ongoing lichen growth problem on Mount Rushmore National Memorial that requires the employment of mountain-climbing conservators to clean the monument.