Summertime in California is a constant reminder of the possible destruction with which we cheerfully live.

The baked hillsides, the relentlessly clear skies, the casually bunched power lines draped lazily along every stretch of highway — enjoy yourselves before the fires come in, this landscape shrieks.

Luckily, there’s one herald of summertime in San Francisco that speaks to renewal.

I’m talking about the goats.

The goats are hired by a variety of city agencies, educational institutions and private properties to reduce fire hazards every year. This year, my first goat sighting was May 20.

I was walking in Bernal Heights, and I happened to come across several small children shrieking with joy, pointing their fingers and collapsing dramatically on one of the streets that abuts the College Hill reservoir.

A quick glance assured me that the children were not reacting to a mysterious poison.

In fact, the kids were having the only appropriate response one should have in our situation, which was being suddenly confronted with a herd of about 30 goats. I gasped, too.

Allowed to roam free within a gated area, the goats were making quick work of the hill’s brown grass, its overgrown weeds, its draping vines.

They ignored our meltdown, because they are professionals. The fires are coming, and they had to eat the weeds and grasses down to a safe level.

“They are so cute I can forget they are these mighty weed-clearing machines,” said Suzanne Gautier, a spokeswoman for the San Francisco Public Utilities Commission. “But they are. And we really appreciate the hard work they do for us.”

I’d called Gautier to learn about what the goats were doing on College Hill reservoir that day — “integrated pest management and weed abatement” are the fancy terms for it. While I was at it, I asked her what else they do around our city.

“The (PUC) hires the goats to go anywhere we have critical facilities in steep neighborhoods, like the Twin Peaks reservoir,” Gautier said. “They’re not intimidated by having to climb steep slopes or deal with blackberry thorns or other difficult weeds. It’s just hard for a human to traverse some of those slopes, especially with a hand mower.”

Still, we might never have had goats roaming San Francisco every summer if not for an ordinance the city passed in the mid-1990s. The ordinance committed the city to using the practices that were the most environmentally appropriate and were the least invasive.

Goats have less of an impact on the environment than, say, gas-powered motors. The way they chow down on the topsoil can actually improve it, and they’re relatively cheap (Gautier said the 2018-19 SFPUC budget for “goat maintenance” was $40,000, as opposed to having two full-time gardeners doing their work in the past).

They just happen to be really cute, too.

“It’s like painting the Golden Gate Bridge — as soon as the weather improves enough for them to be rotating among our facilities, they’re out there all season,” Gautier said. “And they bring happiness wherever they go.”

San Francisco is not the only city in California that uses goats for weed abatement. As I delved further into the business, I was surprised to learn how competitive it is.

“The cost of keeping animals in good health is quite high,” said Genevieve Church, executive director of City Grazing, a goat landscaping nonprofit located in the Bayview. “The expense of running a small company is huge in San Francisco, regardless of what the profession is. And there’s a lot of competition for clients.”

Even in the crushingly future-oriented Bay Area, there are plenty of people who aspire after the ancient profession of goat herding. Green Goat Landscapers and Rent A Goat are just two businesses that provide Northern California goat service in competition with City Grazing.

We’re not even touching the hypercompetitive goat-dairy industry, which Church doesn’t do. “The taste of invasive weeds in vacant city lots — no, I don’t think anyone wants the milk from my goats,” she said.

Church’s clients include the San Francisco sheriff’s office, UCSF and others. She also makes it work by offering yoga classes with baby goats and goat rentals for “special events.”

It helps that the City Grazing herd is hardy enough to live near the S.F. Bay Railyard, a rugged location that Church attributes to the goats’ “urban savvy.”

“My goats will choose to sleep on a concrete slab instead of on comfortable grass,” Church said. “They will look at your pit bull on a leash and know they don’t have to worry about it.”

That’s not a license to bring your pit bull around the goats, of course.

Church also urges the public to leave their vegetables at home. “It seems like fun, but it’s counterproductive for their digestion,” she said.

There you have the simple rules for life around the goats of San Francisco. They’ll be traveling around our city all summer, so if you see them, stop and wave hello — they’re more than just cute animals, they’re making San Francisco a safer place.

Caille Millner is a San Francisco Chronicle deputy opinion editor. Email: cmillner@sfchronicle.com Twitter:@caillemillner