[joe_the_user]

"...tree growing to sequester carbon is very complicated, there's a lot we don't know, and there are a ton of different outcomes depending on how/where the tree growing is carried out.."

My guess is they say that because that's a much as they can say with full evidence backing. But suspect that most ecologists actually want to say "planting tree is a dumb solution for carbon sequestering or anything, please stop". That's what my ecologists say, certainly.

I mean, consider:

A) Trees are very good at spreading themselves. A tree adapted to it's environment will spread everywhere.

B) You can't get more carbon into an environment than ecosystem naturally sequesters - what it sequesters in long term, what's at the end of forest succession [1]. I'm in the California Sierras now and a lot of areas have a higher density of trees than the long term average and this along with global warming has contributed to the massive summer fires we've had. If anything, what this area's ecology needs is a thinning of the stick-like trees that have grown over the last 100 since all the existing trees were cut down during the Gold Rush. That can happen through fire or through human intervention but since human intervention is costly, fire is what it will be - fires made worse by fire suppression over many years. California's ecology is "fire based", etc.

https://en.wikipedia.org/wiki/Forest_succession