It's a well-known fact that lichens are useful environmental indicators. Lichens are much more plentiful in the western woodlands of the British Isles, for example, because they are very sensitive to sulphur dioxide pollution, and so the clean air blowing off the Atlantic is better for them.

However it's not the case that all lichens are slow growing, sensitive organisms. Some are quite rapid colonisers, and grow in the most unpromising of situations, as The Ranger noticed when parking his car next to a blue Ford in a town-centre car park recently.

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You'll notice that this car is only six years old - the rest of the numberplate is obscured to protect the innocent. Closer inspection revealed more interesting features though:

Two common crustose lichens, the more tolerant type, have become well-established on this car's badge. So they can't be more than six years old - or probably less, assuming that this car's been washed at least once in its life. It's probably also fair to say that the rear end of a car is one of the least promising environments for good air quality.

On the high-level brake light is an impressive forest of lichen. This is the first stage of colonisation: if left alone, these little organisms would eventually start to build up a layer of organic matter which might eventually turn into soil, and higher plants would soon get a foothold. The Ranger has seen moss, lichen and algae on road-going cars, but never yet a leafy plant. Can anyone oblige?