An easy way to contribute to tree planting is ecosia.org (more info at info.ecosia.org). We've already planted more than 55 million trees and won't be stopping there.
I linked this a different comment: https://www.youtube.com/watch?v=-ld0EDDQZg4& This is our tree planting officer explaining (among other things) how he tries to make sure we plant in the right places (and that includes land ownership questions and how to make sure the tress will still be around in a few years).
As for energy consumption, we do offset the CO2 emissions that are associated with searching on Ecosia by running our own solar power plant. Here is some more information on this on our blog: https://blog.ecosia.org/co2-neutral-seach-engine-ecosia-sola...
We work very closely with experts from experienced tree-planting organizations to make sure the best possible methods are applied. Our tree-planting officer (yep, that is his actual title) has years of experience and is our link to these partners on the ground. Here is a video of him sharing some more insights of how we pick trees and planting sites: https://www.youtube.com/watch?v=-ld0EDDQZg4&
Not sure if this is appreciated on HN (I only saw a guideline about posts, not comments), but if this piqued someone's interest, we have a bunch of open positions at the moment: https://ecosia.workable.com/