Well, it seems to be all down to the kids and a few geriatric cinema performers.The tree planting in itself is not the issue it is the psychological effect that having a global population focused on accepting climate change (crisis) requires a solution... that is... IMO it would give people a common cause and hope and a sense that they can do something about it all...
It should be no problem getting young volunteers for tree-planting projects (our newly elected federal government has one in its platform), and the government - as well as corporations that could use some public good-will - might do well to hire labourers made redundant by automation. There's a ton of urgent remediation and retrofitting to do on ocean-front and northern communities; dam-building on flood-plains, moving vulnerable installations, etc: plenty of work to replace the oil-fields and coal-mines.
To me, the most important mitigating strategies should be
1. demand-reduction. It starts with eliminating the unconscionable amount of waste, maximizing the efficiency of resource use, transportation, food production and housing .
and 2. distribution of energy generation. "The grid" has always been a bad idea: sloppy, dangerous, expensive, wasteful, vulnerable, costly to maintain and unsightly; in the prevailing climate, it's flat-out insane - and that's what they're hooking the wind farms and nukes into.
But politicians are afraid to tell people they can't have the good old days back again.