Can you be more precise? Like an actual area on the map. Because when I look at England's map of greenbelt areas [1] literally everything around Birmingham is protected.
[1] https://www.cpre.org.uk/interactive-map-of-englands-green-be...
I think they were joking. In a literal sense, cities require green spaces for water management. Otherwise you end up like Chicago where they paved everything and flood constantly.
Green belt areas mostly are not markers of ecologically important areas. They're a planning tool that largely exists to prevent urban sprawl. A lot of the green belt area is unremarkable commercial agricultural land.