The recommendation is to reforest 103 million hectares of the US. That is about 400,000 square miles in a country of about 4,000,000 square miles, i.e. 10% of the surface area. It's not clear where there is that much land suitable for forest that is not being used for ag and other purposes. Of course, we could decrease the amount of land used for agriculture, since we are continually in surplus and export a lot of foodstuffs.
Some parts, such as New England, were farmed more intensively and have been allowed to go back to forest. In other areas, such as the midwest, poor or swampy land that was used for dairy farming pastures is no longer needed, since dairying is now concentrated in fewer huge herds. However, in these cases land had been allowed to go back to forests naturally, with scrubby transition shrubs and trees that are pretty poor forests. We could get both more carbon capture and more forest products by better forest management in the US. Invasive species such as kudzu, asian bittersweet, and porcelain berry make transitioning back to mature terminal stage forest difficult and expensive.
Some parts, such as New England, were farmed more intensively and have been allowed to go back to forest. In other areas, such as the midwest, poor or swampy land that was used for dairy farming pastures is no longer needed, since dairying is now concentrated in fewer huge herds. However, in these cases land had been allowed to go back to forests naturally, with scrubby transition shrubs and trees that are pretty poor forests. We could get both more carbon capture and more forest products by better forest management in the US. Invasive species such as kudzu, asian bittersweet, and porcelain berry make transitioning back to mature terminal stage forest difficult and expensive.