A Chartered Environmentalist and Fellow of the Chartered Institute of Ecology and Environmental Management, Gary was the author of the GLA and City of London reports on the Urban Greening Factor.

He is author of The Water Sensitive City (Wiley 2016), Ecosystem Services Come to Town: Greening Cities by Working with Nature (Blackwell-Wiley 2012) and Green Roofs and Facades (BRE Press 2006) and contributor to Nature Based Strategies for Urban and Building Sustainability (Elsevier 2018)