The Silver Strand “Tombolo” (spit of sand joining a mainland to an island -in this case Coronado) could be in trouble with rougher El Niño weather to come.

I’m at the bus stop. The one right outside the Bullpen bar in IB. Problem: last bus heading north to Coronado is gone. It’s after midnight. I’m broke. No way up the Silver Strand. And believe it or not, phone’s dead.

Hoo boy. Really blew it here. I look at all those empty seats in cars speeding north. I think of all my friends, cozy in their beds. Then I think, Come on. Don’t be a wimp, walk it. It’s just a few miles. OK, maybe eight. OK, nine. Still, good exercise! How many people in the history of this place have walked or pedaled or run that distance? Kumeyaay had no choice. The Spanish pioneers had their horses. The Victorian holidaymakers had their steam-train line from here to Tent City — the Hotel Del’s holiday tent homes that were the hit of the first four decades of the 1900s. Whatever, I can do this!

And so I start walking, up the long curve of Silver Strand Boulevard to where it takes its leave of Imperial Beach. Oh man. Taking time, energy. I follow the bike path. No bikes. Not this time of night. Traffic zinging past gets less frequent, too. Silence gets louder. Unseen animals rustle. I hope they’re not snakes. I think of the California Least Tern, which is supposed to live near these tidal ponds, the ones that are glowing dank in the moonlight. Then on the left, I spot the new Navy SEAL base, the Silver Strand Training Complex. I worry about someone shouting “Halt! Who goes there!?”

After a couple of miles, I’m exhausted. After six or seven, I’m putting one foot in front of the other — just. By about four in the morning, I’m totally punked. I have to sit down, lean against something, get some sleep. Because yes, I had a couple of Arrogant Bastards at the Bullpen. I lean into the bushes and collapse in a nervous nap. I hear more things scurrying away in the undergrowth. I worry about surprising other people who are sleeping rough. But actually, it’s a beautiful rest in this silence, with only the zing of crickets to sing me to sleep. When I wake up, the sky’s gently suggesting morning. And hey, I find a seat. I know a lot of volunteer work has been going on. Is this what they call “Nature’s Bridge to Discovery”?

I also realize that I’m seeing a timeless, shadowy Silver Strand, the barrier against the ocean that made the miracle of San Diego Bay possible. And it’s only when — finally! — I make it home at around seven in the morning that I realize what a piece of history I was tramping through.

“This narrow barrier of sand is the western landform enclosing San Diego Bay, the largest natural bay in Southern California,” writes Scripps Institution of Oceanography. It says the Silver Strand formed as sea level rise pushed the coastline into the wave shadow of Point Loma. “A reverse eddy transported sediment north from the Tijuana River delta, extending the sand spit, and eventually creating a tombolo [a sandbar that connects an island to the mainland] with North Island. Completion of the tombolo marked the origin of San Diego Bay. Today, artificial dunes 3 meters high on the Silver Strand protect the Bay from storm overwash [but] make future sea level rise a concern.”

Scripps says archeological sites prove that mankind has been coming and camping on the Silver Strand for at least 5000 years. But now, Scripps is worried that the Silver Strand may not survive climate change. That at some point storm waves are going to punch a hole through and let the ocean into the southern end of the Bay. “Once a southern entrance has opened, northerly [sand] transport will shoal the Bay and prevent tidal flushing. It would also provide an entry for high-energy ocean waves that damage harbor installations and cause flooding. Only massive nourishment projects totaling more than 26 million cubic meters over the past 60 years have prevented erosion of Coronado beaches and the strand itself. More will be needed in the future if sediment flux out of the Tijuana river basin is not restored.”

Maybe it was me, but I have to say, last night, the Silver Strand did look vulnerable, felt vulnerable, and not only because that’s what I felt too, as I put one foot in front of the other.