While trees are great and you have a point, we can't just put trees everywhere without consideration of native species. Much of the U.S. for example is prairie/grasslands that doesn't have a high tree density and the carbon is cycled much faster. Also of concern (not my concern but somebody's) is the property value of land used for trees instead of profit.

A acre of hemp regrown every year and a biochar retort could sequester far more carbon than an acre of forest over a given period and can be done on "wastelands". Biochar IMHO is the only carbon sequestration method that actually makes sense.