Exeter is named the UK's greenest city centre according to its green spaces.
The University of Sheffield study analysed the hearts of 68 urban centres and ranked them on tree cover, its vegetation and the amount of parks.
It found Exeter to be the greenest, followed by Islington, Bristol, Bournemouth and Cambridge.
Mark Ashdown from Bristol Tree Forum said they were "pleased to see this report, though it would help to know what part of the city was surveyed".
Trees, vegetation cover and public green spaces have been shown to have positive impacts on biodiversity and human health, the authors said.
Bristol is adding to its green credentials by introducing a launch a Clean Air Zone to tackle high levels of traffic pollution in the city centre.
Glasgow was ranked the least green by researchers, followed by Leeds, Liverpool and Sheffield and Middlesbrough.
While previous studies have looked at the greenness of whole cities, including broader suburban areas, this research is the first of its kind to focus specifically on the heart of city centres.
Researchers said the findings showed a "clear divide" between the south of England and former industrial heartlands in the north.
Senior author of the study, Dr Paul Brindley, said it "clearly highlights the need to urgently improve the greenness of city centres at the bottom of the list, and to ensure that action is taken by local authorities to close the gap".
Mr Ashdown said: "We note however that, for tree cover, we come eighth and are probably on a downward trajectory due to the loss of our city centre trees without sufficient new replacement tree planting places being made available."