We're around 31M trees now

Hyde Park shows as an empty space. Hyde Park does contain trees, but the park is administered by the Royal Parks Commission, which is controlled by central government, not by the Greater London Assembly directly or indirectly.

And in South West London there is a large expanse where the only trees are along the A23 road which goes from South London to Brighton. I presume that the local (borough) authority doesn't collect tree data here. But that road, like many large through roads, is controlled by Transport for London, not the borough.

Apparently they get a lot, even more than 12 years later: https://www.abc.net.au/news/2023-05-21/tree-love-letters-for...

I turn to https://calscape.org a lot for inspiration and information on plants and trees to plant in my California garden.

For what it’s worth, when it was posted here before, I raised an issue with a link to an additional data source as requested, and it’s still open five years later. I don’t think this is actively maintained.