He was one of the early users of lichens as indicators of air pollution, and also studied the ecology and diversity of wildlife in urban areas.
His parents were Ruth (nee Ainsworth) who wrote books for children, and Frank Gilbert, managing director of Durham Chemicals.
While employed at University of Newcastle upon Tyne, he started research for a PhD degree on the subject of Biological Indicators of Air Pollution which was awarded in 1970.
He carried out research into the distribution and effects of air pollution on lichens and mosses and showed that their diversity reduced in moving from countryside to industrial urban areas.
[2] He learnt how to identify the lichen flora of the British Isles in the 1960s and went on many field visits to record more unusual species, and their locations in more remote parts of the country.
[2] The Caledonian lichen Catillaria gilbertii was named in his honour by colleagues Alan Fryday and Brian John Coppins in 1996.