Golden Shield Lichen – Xanthoria parietina

Also called ‘Yellow Scales’, this is a bright striking foliose lichen, which is golden-yellow to orange, and is green where shaded from the sun. The disc like structures are more orange with a pale margin. Thallus up to 8cm across.

Found mainly growing on sun exposed bark, but also rocks and walls, roofs, paving, and other man-made structures where nutrient enrichment via bird droppings is found. It is particularly common in coastal areas where the multitudes of seabirds provides the nutrients which it requires. Common and widespread throughout the British Isles.

This organism is made up of a single-celled green algae which feeds the fungi in return for moisture retention in times of drought, and  also for acting as a sun block from UV radiation with its yellow pigmentation.  Xanthoria parietina is particularly resilient to pollutants such as nitrogen and ammonia, and actively thrives on them, which makes it an excellent biomonitor for measuring levels of toxic elements in any given environment.