There is very little "abandoned" land today. And, it depends on what we mean by "agriculture." Tree farming is a major industry in our country. Even the publicly owned parks and forests are managed to produced wood products. When tree farming, private and public, is added to traditional farming, I'd expect to see something near 90 percent of the land in the Eastern US in agriculture. Even the mountains are managed for tree production. But even still, I'd have a hard time accepting the idea that we have more "trees" today than when the Pilgrims landed. I've seen the stumps left from the harvest of virgin trees in Souther Swamps. We can only imagine what a forest of 175 foot tall yellow pines stretching from Texas to Virginia was like. The number of trees may be greater today. But, can we compare the 40 to 60 foot typically harvested tree of today to the giants of that time. I don't think so.