Where in the UK are nitrogen-loving lichens more common? Can the public identify lichens? What have you helped us learn about air quality?
These questions and more have been tackled by OPAL scientists studying results submitted for the OPAL Air Survey.
Their investigation of the link between lichens and air pollution was published last year in the journal Environmental Pollution.
Now lichen expert Pat Wolseley and OPAL data manager Laura Gosling explain the science behind that article and look at how we analysed your data.