This might be better as a cross-post with AskScience, but I am also curious about the historical component. The Northeast was, in large swathes, considered completely deforested due to agriculture and the appetite for wood and charcoal in early industry. Did tree seeds in the soil seed bank survive the full duration of this period of deforestation? Or was it a gradual spread, or did people in the Northeast help along the process by planting new forests?
Additionally, since this is such a dramatic change to a landscape, I am curious how Americans of this region reacted to, and felt about, the change from a widely-deforested environment to one that was quickly returned to forest cover. Did people notice the change happening? Did they have some sense of unease as farms and pastureland was swallowed up by the old "howling wilderness" that their ancestors had described? When old farm towns were abandoned and forests overgrew them, did Northeasterners feel a sense of community decline, like someone in an old factory town watching a boarded-up abandoned factory crumble?
Since it seems that the notion of progress would have been in many ways different in the 19th century than our notion of it today, I am wondering if they saw the regrowth of forest as a bad sign rather than a good one!
I had to dig around, but I found an answer that I wrote a ways back that might be relevant.
Some important snippets. First, it's important to note that the idea that the Northeast, or specifically New England, was essentially abandoned by a mass flight of farmers actually comes from a 1927 article in the Geographic Review titled "A Town That Has Gone Downhill".
Apparently there were real deficiencies with this theory, however. First, it tended to flatten wide varieties of agricultural land in New England: not all of it is stony hillsides (the Connecticut River Valley is practically Mid-Atlantic, to the point of producing tobacco). Nor was all of the land in agricultural use actually tilled: apparently something like a third of agricultural land was tilled, a third used for pasturage (think Vermont cows), and the rest woodland or fallow land. So much of the rocky, hilly areas were used in the 19th century for sheep and wool production.
Furthermore, apparently actual agricultural figures from the late 19th and early 20th century do not bear out the decline model: yields per acre in New England were among the highest in the country, with produce even being exported to other regions (apparently Boston-area vegetables were sold in winter markets in late 19th century Florida). Fertilizer use on New England farms was high (but not higher than in the rest of the East Coast).
Agricultural land use in New England seems to have peaked around 1880 (around 50% of the total), before showing a small decline in the late 19th and early 20th century, but even during World War II the total land under agricultural use was some 35%: after 1945 it crashed to around 10%.
There was a shift among young people from about the 1860s or so to seek industrial work in towns and cities, rather than continue agricultural labor, but the shift actually was a steady one over a century or so that only finally saw much former farmland revert to forest (or suburban developments) in the post-World War II period.