London GDP is about £500 billion. They’ll need this info to maintain the trees in any case. If it cost 100k, it would be 0.02% of GDP. For the difference trees make to urban areas, it would be utterly trivial. If you made £50k cash after tax a year (so closer to 80k before tax), it would be £10 a year, that’s the fraction.
Of course it costs far more than £100k to maintain this data.
I think most Londoners wouldn't want to pay £10/year for a tree database.
Imagine a sign saying "Just donate £10 so we can have a database to tell us where our trees are", I bet the vast majority of Londoners wouldn't hand over £10.
Even a keen gardener wouldn't likely pay £10 to have a map of where all the vegetables in their vegetable patch were.
One of the benefits of representative democracy & taxes is that individuals don't get asked about spending for each line item. That decision lies on the people chosen (directly or indirectly by the public) to make those decisions based on better experience than the general public has. Problems tend to arise when small numbers of people try to micromanage government spending & actions by enforcing their minority views directly on the actions of government, not via representative elections.
Trees can be a hazard. Roots and branches need to be monitored, for tripping or falling risks, or the risk of the tree falling over. Trees need to be trimmed, especially where they intrude into problem space - cables (very rare in London), double decker buses, people's property, and so on.
The database needs to be built.
Also as someone else pointed out I got my maths wrong (I blame no calculator on an ipad): it is about 1p from 50k a year. I calculated with 500 million not billion.
Trees can be a hazard. Roots and branches need to be monitored, for tripping or falling risks, or the risk of the tree falling over. Trees need to be trimmed, especially where they intrude into problem space - cables (very rare in London), double decker buses, people's property, and so on.
Of course it costs far more than £100k to maintain this data.