US launches $1bn tree-planting scheme to mitigate effects of climate crisis

Montreal has been "greening" the city for a decade. I'm fortunate enough to be able to walk to work. The last 2 summers I've had to reroute my walk (adding 10 minutes) so I can stay in the greener parts of the city. It's easily 3-5°C cooler on the streets with green areas. When it's 35°C out... it's really noticable. It must have a mental health effects too because it's a god damned joy to walk to work now.

Not if you are looking at mitigating heat in cities. A 6ft tree will be giving a decent amount of shade after 5 years' growth if you pick the right species. The trick is looking after them.