If there are a billion people in the world able to plant trees, that's a 1000 trees each. That's about 10-20 days of work per person (I have planted about 50 trees in half a day once). You're right, this would be easy.
You will need land which don't encroach on agriculture or other industrial use land. Land which gets enough rainfall every year. Also planting is just one step in the process , you will need to maintain it, if the trees actually have to grow.
tree planting ≠ forest planting.
But on that notion a “productive” artificial forest solves this issue.
build forest with plants that provide utility. But are family to the local environment. it’s a concept that has been proven
Would you not then need to wait until they were mature enough to have extracted a large enough quantity of Co2, and then chip them up and bury them back underground where all the oil came from in order to net extract Co2 before planting new trees in their place and going for another round.
Otherwise the Co2 will be returned to the atmosphere once the tree rots or is burned for fuel.
Forests that we don't cut down is called reservations.
In Sweden there is a law that states that any forest cut down must be replanted unless used for farming or new buildings. I also recall Norawy having the similar law. If we counted that as carbon removal, we would have a massive carbon net negative from this pretty old law.
The law is not a carbon removal strategy. It simply maintain current biomass over time.
fruit trees mostly also, air cleaning + food (and great food), double win. Figs, clementines, mandarines (currently I'm finding so many around, just on the ground, in more or less abandoned gardens), persimmons, medlars..
Well with some quick google search, in the US there's an average of 4816 trees per acre of primarily forest land, so 1 trillion trees you'd just need 207.641.196 acres.
The total area of forest land in US is 501 million acres, with 2.5 trillion trees of all types.
So you'd need to just find 207 million acres of viable land, 1 trillion saplings and enough people to plant them.
In my point of view, that's a bit challenging - but I'm no expert in such matters.
I think it is important to note that the 4816 figure - presumably from the Forest Services report on New England forests - includes on average 4600 immature seedlings and saplings which will not reach maturity due to space requirements, and 200 trees with trunks larger than 5". Even if we consider an aggressive distribution of 750 trees/acre you're planting a landmass equivalent to 10x California. Challenging indeed!