They have done that a lot in Utah. In fact a lot of the Topo maps are all based on 1978-1980 surveys and are obsolete compared to what you can find on Google Earth which are based on recent sattelite photos.
In 2000 while riding in the strawberry area, They had a track excavator take 5 miles of road out. The road had been closed for 10+ years. But ATVs frequently went around the signs and rode along the road. So heavy equipement literally ripped the road to pieces. It was very unpleasant to ride a horse down what remained. I remember thinking at the time, " What a horrible mess the Forest Service just created".
Winter snow, summer rains, the passing of natural game and herds of cows and sheep have turned what was a very rough mess into a reasonible trail that we still ride. And it didn't take long. They accomplished what they set out to do. Stop the ATVs from driving along that route.
This is that same road, 12 years later.
The trees are missing where the road was. The ground has erroded off what once was a flat track, into what you see as slope. The rough up and downs have erroded into a level trail. I can't guess how many cow and sheep hooves have beat it down to what you see. It still shows on the National Geographic Topo maps I print out as current road.
In fact the 9 riders I had out from South Carolina in August commented. That as they watched their GPS as we rode, that we were riding on what their GPS's showed as roads, That were nothing more than trails.
Another example that used to be a road. You can see the flat road bed with only a single track now in use
Other examples are the canyon that I hunt. The Forest Service closed that road in 1983. I remember as a kid riding with my dad up that road in our pickup truck with a camper on the back and actually seeing a cadilac pull a boat up that canyon. Once the road was closed. Mother nature took over and has washed the road out entirely. In fact in 2008 it totally flash flooded and took out 4-6 feet of earth down the entire canyon. It was really tough to even get the horses up what was left of the canyon. The rancher who ownes the grazing permits, brought a track-hoe in and did a little work to remove some ledges and at least make it horse and cow friendly so he could herd his cattle up the canyon to graze.
You can see how high the old road bed was vs what has erroded off. The old road bed is higher than my friends hips sitting on a 16H horse.
Here the Forest did nothing other than let nature take it's course.
In many areas I've fine with what they have done. Closing down some roads has returned much of Utah to a more natural state. But I don't approve of their more recent actions as they get more agressive in closing more used roads. It is one thing to close down a old loggin road. It is something else to close down a county road that has been main tavel route for those who live in the area.