I would have just posted this initially, but I was on my phone and had just typed a giant post. On the laptop now!

Deforestation is when undeveloped land becomes developed. It's almost always permanent too, and is usually done in a reckless manner. The wood not processed correctly, animals not moved, exotic plants not relocated, that sort of thing. The clear cutting process for the forest service is incredibly delicate and detailed, and the top priority is nature's well being. Depending on the forest's integrity, we might even do what is called a prescribed burn where we dig fire lines (among other meticulous stuff) and burn off a section of the forest. It's never because we need to pave over it or something, it's because the forest's integrity had dropped below a safe line. If this isn't done, there's a very good chance the forest will ignite from lightning strikes or human involvement, and when we don't already have fire lines dug it can spread well beyond our control for weeks on end, destroying houses, perfectly good forest, etc. Some forests get "overgrown" and shrubby; this is usually the result of some sort of tree blight that kills off a main tree in that particular forest. There tends to be a lot of dead downed trees that kill undergrowth and warp the ground, causing odd pockets of water. Just generally messes with the whole balance, and eventually becomes a huge fire hazard. We do everything we can to prevent the forest from getting to that stage, but dealing with pine beetles and gypsy moths in a massive forest isn't exactly easy. The whole thing takes a lot of time and there are a ton of people consulted; foresters, loggers, biologists, ornithologists, etc. Nobody in the forest service can just decide "hey let's cut this forest down," which is apparently what some people actually think. Before any action is taken, there's a huge plan laid out about the recovery. Ideally, a whole forest comes back to "normal" in about twenty years. That's a really general statement, and of course there are numerous factors that alter it or even encourage it. But yeah, twenty or so years. Might sound like a lot, but think about how long nuclear waste lasts. How long we have until oil runs out, that sort of thing. Furthermore, if you cycle the forest correctly you can maintain a perfectly healthy forest while still cutting bits. Conversely, I've seen the destruction of an arboretum to build a giant concrete circlejerk. The only trees and plants that were saved are the ones that me, my dad and some other forestry people took. Thanks for reading if you made it this far!

Edit: I also wanted to let everyone know that the forest service doesn't use pesticides and herbicides the way some other people are describing. We use ladybugs, certain fungus, etc. We also spend a lot of time cultivating the soil so that when plants grow back it's in a healthier foundation, so ideally we won't have to burn it off anymore. We also try to keep invasive species out when reseeding (kudzu, mainly) and nuisance trees like the Virginia pine. The Virginia pine is a scrubby, shitty tree that barely keeps a full plume and catches on fire like nothing else. It also has one of the lowest respiration rates of any tree.

Which brings me on to respiration - a younger tree, and more specifically the new growth has more respiration than older growth. The tree converts energy as a tool for growing, so the early stages of a tree have much more conversion going on. So there's that aspect too, converting about twice as much (depending on the species, there is more specific data) carbon dioxide than an old growth forest.

Don't get me wrong though, a lot of old growth forests should be kept around. National parks are good at keeping their land uncut, which lets you see things like massive sequoias, redwoods and petrified wood. There are also things called "constitutional forests," which are essentially the original trees that were here when Europe arrived. Apparently unbeknownst to most, almost the entire east coast was cut and developed or simply logged by us white devils back then. There is very rarely a tree you'll find on the east coast that's more than about 200 or 300 years old, but when you do find these forests it's probably best to keep them the way they are. Here is an example of one forest battle going on in my town right now. I haven't read this website, but it seems to be the "official" one - knowing my town, though, let me apologize for some of the hippie propaganda you may encounter there. I've walked around those woods, and most of them seem to be about ~300, with some looking closer to 350. There are also some rare trees in there. I remember seeing black oaks, which the white oaks pretty much beat at evolution some time ago. There are also a lot of cool ferns and some interesting birds. So when I talk about clear cutting, I mean stuff in the middle of the national forest or on some guy's private land - not 11 acres of old growth in the middle of town. There are about 1.8 million acres in the forest I work on, to give you some idea.

TL;DR: Shit lots of information on forests.