1% add up if we can do it worldwide on a regular basis. (likely yearly, but you need the proper forester for each forest)
Further, even if we didn't face the issue of running out of land, we don't appear to be able to actually plant trees fast enough and well enough (many of the "millions of trees" planting projects, especially in developing nations, have had tree survival rates of under 10%)
Forests help and are part of the strategy, but fundamentally not moving the needle.