This crustose lichen is found in abundance in this area - most patches are bleached white (sulphur dioxide?) but there are some lichen which are slightly greener.
Caution: Do NOT use iSpot to identify fungi to eat!
Some fungi are very poisonous so a mistaken ID could have serious consequences.
No interactions present.
Whiter thalli are probably just drier. I don't think it is overly bothered by current sulphur dioxide levels anywhere in the UK, not even on the fringes of Manchester.
Lat/Lng: 53.4566, -2.3372
OS grid ref: SJ777955
These lichen are ubiquitous on the pavements in the area. However, the largest and healthiest patches are found on areas where there is very little trampling. This particular photograph shows an area where people generally do not walk.