The pro-tree-farm argument goes like this: When you plant a tree, it goes from seedling to full-grown plant by rapidly extracting carbon from the atmosphere, including carbon that humans have emitted by burning fossil fuels and raising cattle. (When a climatologist looks at a tree, he sees a leafy pillar of solidified greenhouse gases.) Once the tree reaches maturity, though, it slows its consumption of carbon. By way of comparison, think of the appetites of a growing teenager and a senior citizen. When you’re done growing, you stop consuming as many calories. The best move, according to some tree-farm advocates, is to replace the mature tree with a new sapling and start the growth process over again.
I tend to think that farm-grown trees have less impacts on the forests. The best trees are always selected to be cut, reducing the quality of the gene pool. Also, having so many people driving on muddy roads tends to cause drainage problems. People will always find ways to allow, or disallow things happening on public lands. One commenter summed it all up as a non-issue, climate-wise.