Trees alone aren't enough. For example, ecosystems like the Amazon rainforest are highly balanced ecosystems that are in a perpetual recursive loop. You can't tear them down and then rebuild them by just planting trees. The rainfall the Amazon gets is itself generated by the canopied rainforest. And you can't bring back all the diversity of life that gets lost.

And this goes for any other ecosystem.

And the staggering statistic is that only 30% of the Earth is covered by forest now, a drop from 60% prior to humans going nuts.

Here's also an article that provides some counter arguments to the original paper: https://www.weforum.org/stories/nature-and-biodiversity/plan....