A couple of years ago, my husband and I were biking on the property adjacent to my family's ranch in New Mexico, along a stretch of overgrown double-track that everyone we knew called the "County Road."

For generations, the locals up the valley had used that road as a shortcut to get from the far reaches of their property to town.

We had traveled the road numerous times, but on this visit, we passed a house under construction and heard the sound of chain saws. A few minutes later, we were chased down by an ATV and two very ornery fellows covered in sawdust.

A tall, red-bearded man dismounted his three-wheeled steed and confronted us, while his short friend glared at us from his seat and placed his hand on a gun he wore holstered around his hips.

They asked us what we were doing there, and I explained that we were riding the County Road, which I understood to be a public thoroughfare. The tall guy said it passed through his property and it wasn't open to the public. The short guy patted his gun.

The tall guy asked where we came from, and when he figured out we lived next door, his demeanor shifted radically. He shook our hands, told us he had recently moved from California and was building his dream home and that he was so, so pleased to meet his new neighbors.

He waved us down the trail, bidding us to pass through anytime (but perhaps, if we wanted to avoid being shot, to call first). We left, quite shaken, and despite the tall guy's gracious invitation, we have never ridden that stretch of road since.

Last week, I found myself tangled, once again, in the morass of private land and public trails.

Since the early 1990s, I have been riding the single-track that spiders off the dirt roads on the crazy quilt of national forest and private land near my parents' house in New Mexico. It never was clear to me whose land those trails were on. I didn't cross any fences or gates, nor did I ever see any "private land" or "no trespassing" signs, so I didn't ask any questions.

Then, last week, as I was riding an ultranarrow single-track that winds through a tunnel of overhanging scrub oak, I turned a corner and encountered a jumble of barbed wire, logs, branches, police tape and "no trespassing" signs.

There were no guns this time, but the message was the same: This land is my land, and this trail is now closed.

Apparently the path, which had been in use for as long as I could remember, ran through private property. I don't know if the property acquired a new owner or if the old owner got sick of all the bikers, but the outcome was the same either way. My favorite bike trail was no more.

As I turned my bike and started climbing back the way I came, I felt, I imagine, like certain lonely cowboys of the last century, crooning "Don't Fence Me In" as the open range was bisected by barbed wire.

Perhaps it's all the lawsuits or perhaps it's the inevitable result of the second-home boom, which has divided parcels of land among more owners from more diverse walks of life - but whatever the reason, the rural tradition of social trails is giving way to a much more circumscribed property ethic.

These closures aren't only in my neck of the woods, of course. Across Colorado, property owners have decided - for fear of liability, theft, vandalism, for reasons of privacy or because of environmental damage - to block access to a stretch of well-loved trail that runs through their land.

Most notoriously, three Fourteeners - mounts Lincoln, Bross and Democrat - were closed to climbers because parts of the mountains are on private property.

Last year, the state passed legislation granting the landowners immunity from liability if hikers are injured on those peaks, but the trails have yet to reopen.

Now don't get me wrong. I understand private property is just that - private - and despite one confusing federal law that guarantees access to certain trails or roads through private land under very specific conditions, I realize in most instances I have absolutely no right to expect people will let me have fun on their property.

But as more landowners close longtime trails that run through their land, many trail users are in for a rude awakening.

Private property is the law of the land. But somehow, this new degree of privacy feels like the end of an era.

Outdoors writer Hannah Nordhaus has lived in Colorado for 12 years.