You can filter by tree type on the official map (which I think shows the same data): https://www.london.gov.uk/what-we-do/environment/parks-green...

Ok, but this only shows about 20 species.

We're doing some interesting work in this field at Cervest (based in London). https://www.cervest.earth/

2 billion km = 2e12m, not 2e9

The fact that individual stars can be seen doesn't necessarily mean the telescope has a resolution equal to the angular size of this star. A point source will be apparent even if it isn't resolved. Otherwise we could never see stars with our naked eye.