'Glowing trees' for greener cities
Future "green" cities could resemble fairylands filled with radiant buildings and glowing trees, a report has predicted.
Spray-on light absorbing dust would give public buildings, roads and pathways a phosphorescent shine at night, helping to improve the safety of parks and alleyways.
Even trees could be made to glow in the dark by splicing bioluminescent genes into their trunks and branches, say experts.
By making street lighting less necessary, the carbon footprint of urban centres would be reduced.
The bright vision of environmentally friendly cities was unveiled by Arup, the engineering and design consultancy behind London's Garden Bridge project.
It looked at ways of protecting urban areas and improving the lives of their residents in a world transformed by global warming and growing city populations.
The report highlights natural solutions such as preventing flooding by replacing hard concrete and tarmac with permeable surfaces, and increasing tree cover.
To meet the increasing demand for food, vertical "urban farms" are also forecast with crops being grown in and on city buildings.
Parks could also contribute to food supplies by providing places where people can forage for fruits, edible greenery and even insects.
Tom Armour, landscape architecture group leader at Arup, said: "By 2050, it is predicted that the human population will have reached nine billion with 75% of people living in cities.
"Adaptations to existing city spaces, enabled by rapid technological innovation, will serve as major catalysts in the shift toward increasing sustainability, resilience and adaptability in dense urban environments."
Increasing the number of green spaces in cities was expected to increase life expectancy by up to five years by encouraging people to take more exercise.
Absence from work through sickness was also likely to be reduced. Research had shown that people who work in buildings overlooking parkland took almost a quarter less time off than those with no green views.
Pro-Teq, a UK company based in Virginia Water, Surrey, already produces a product called Starpath that can be sprayed on any solid surface to make it glow in the dark.
The coating contains particles that harvest the sun's rays during the day and emit a soft blue light at night.
"Starpath has the potential to reduce the need for complex lighting installations in parks and alleyways while allowing for the introduction of lighting and the safety and security that brings," said the Arup report. "Another benefit is that since it's non-reflective and relatively low intensity, it doesn't add to light pollution."
A public footpath constructed with Starpath is currently being tested in Christ's Pieces park in Cambridge, UK.