Air Survey results

In the OPAL Air Survey, our citizen scientists record the cover of lichens that are sensitive or tolerant to large amounts of nitrogen pollution on oak, ash and sycamore trees. They also record the number of black tarspot symptoms on sycamore trees. 

What have we found?

 The data submitted by OPAL participants shows that:

  • The air pollutant nitrogen dioxide reduced the number of tarspots on sycamore, once it exceeded a threshold concentration; previously, this disease was only thought to be sensitive to sulphur dioxide
  • Nitrogen tolerant, but not nitrogen sensitive, lichens are less common on oak than on ash and sycamore, possibly because it has a more acidic bark
  • In areas with high levels of atmospheric nitrogen from agricultural sources, there was lower cover of tree bark by nitrogen sensitive lichens
  • In areas with high levels of atmospheric nitrogen from combustion sources, and close to busy roads, there was greater cover of tree bark by nitrogen tolerant lichens

​Academic publications

The following scientific journal papers used OPAL Air Survey data:


See results on the OPAL Data Explorer

Explore the OPAL Air Survey results and draw your own conclusions. Use the OPAL Data Explorer to:

  • Map and graph all Air survey data
  • Find out what lichen species have been found near you and what these suggest about local qir quality
  • Analyse your results and compare your results with others'

View Air Survey results on the OPAL Data Explorer (opens in new window)

View more results

Next steps

  • Useful links - our guide to finding out more about air quality, trees and lichens