Nyna Lynn and Grace.

Partly because it was International Wetlands Day last Saturday (February 1), I thought I’d do a hard-hitting investigation into how we are doing in San Diego. I got down to the Tijuana River Sloughs, famous for preserving 25,000 acres of salt marsh (think three Central Parks), and I was walking past all the rich farm smells of the horse ranches on Hollister Road when I happened by “San Diego Beach Rides,” and I had a thought. Maybe I could do this in style. Hire a horse and ride through the river bottom lands. Appropriate, too, because it turns out the world’s original horse is an American evolution that finally made it to Asia and Europe. Not the other way around.

Half an hour later, I’m swinging my leg over Grace, a 10-year-old filly who’s mine for an hour. Sixty bucks. Plus I get the company of Nyna Lynn.

First time ride for the lady.

I couldn’t have gotten a better guide. For starters, she and her nag make sure we all keep things down to a small roar. No racing through the marshes. No racing, period. Good, because I had forgotten how long it’s been since I told a nag not to wander off into the tall grasses to grab an extra lunch. Or since I remembered just how thigh-splitting a wide horse’s back can be. Or how rough that rumpling movement of Grace’s walk is. It makes you — as Nyna reminds me — move your lower body back and forth while keeping your upper body ramrod straight like an Irish dancer.

“This is work,” I say.

“No, it’s exercise,” Nyna says. “You’re burning up to 200 calories an hour. Of course, that’s if you’re walking, trotting, and cantering.”

A big bird swoops off a branch in front of us.

“Peregrine falcon,” says Nyna. It disturbs another.

“Red-tailed hawk,” Nyna says. Then a third, and a fourth falcon. This eco-system must be rich, to sustain so many predators.

Two rabbits scurry into the undergrowth.

“Rabbit!” I say.

“Wow,” says Nyna. Then we get a succession of white egrets, staring like they’re about to strike. It’s muddy, but not so much watery right here.

Rampant stallion welcomes you.

“Bit shallow for fish, isn’t it?” I say.

“They’re after lizards,” Nyna says.

One thing about this ambling pace: You get time to see stuff. Or to learn about local inhabitants, including long-tailed weasels, voles, deer mice, coyotes, bobcats (“in the evening,” Nyna says), plus gray foxes, striped skunks, bats, rattlesnakes, California king snakes...370 species of animal in this little paradise. Not to mention incredible rare plant communities. Or sheltered waters for the millions of birds that land here for a desperately-needed pit-stop on their South America-Alaska flyway.

Yes, you can hear distant choppers at Ream Field practicing touch-and-go. But overall, this valley is so quiet you catch all the little bird and animal sounds near and far.

No doubt: this is a national treasure.

Except, hate to admit it, I’m relieved to see civilization again. My butt is sore. My back is sore. My thighs feel like they’ve just been through childbirth.

But small sacrifice to celebrate — who knew? — International Wetlands Day. We have, by the way, Richard Nixon to thank for making this part of his “Legacy of Parks” program in 1971, thus saving it from developers.