Teena Borek wants you to help “Save American Family Farms from Extinction.”

Borek grows heirloom tomatoes, leafy greens and fragrant herbs on the Homestead farm she runs with the help of her sons. She doesn’t want to see it go, much like many other farms already have in deep South Miami-Dade County.

That’s why she started the SAFFFE initiative, to encourage fruit and veggie lovers to demand local produce from their neighborhood supermarkets.

Borek hopes people will take the pledge to survey their regular grocery store for goods grown nearby, to encourage friends through social media to shop at stores that carry local produce, and to ask supermarkets that don’t carry greens grown at Miami-Dade to start doing so.

“The most important people are the customers. So if all the customers join together in a grassroots effort, and only shop at stores with local produce, the stores will change,” Borek said.

But don’t join SAFFFE for Borek’s sake, she said: There are health and economic reasons for eating closer to home. And it may be good for not only your health, but also for national security, local food supporters say.

Local fruit and produce can be more nutritious than the stuff imported from faraway places, according to a 2007 white paper written by Kathleen Frith for Harvard’s school of public health. Greens can lose nutritional value if they are handled or stored improperly, and some veggies that aren’t left to ripen naturally aren’t as good for you, according to the paper.

Eating locally also boosts the local economy. Farming (including nurseries) has a $2.7 billion economic impact in Miami-Dade alone, according to the county’s agricultural manager, Charles LaPradd.

“It is an economic engine. It’s a job creator,” he said, adding that all of South Dade’s farms are family-run.

More than that, it’s a security issue, Borek said.

“You can survive without oil, You can’t survive without eating,” she said.

LaPradd added: “If you don’t produce it, then you’re beholden to offshore producers.”

That’s already happening, perhaps more so in the tomato business than in any other market in south Miami-Dade.

Growers say cheaper Mexican tomatoes have pushed prices down to the point of unprofitability. Last season, grocery stores bought tomatoes for $4.50 to $5 per 25-pound box, LaPradd said. That’s way below farmers’ break-even point of about $8.50, he said. Tomatoes grown elsewhere are cheaper to grow, and therefore growers can brace the lower sale prices.

As a result: “There’s farm land for sale. There are people who are not farming this season,” LaPradd said. “I was on the phone with a gentleman today who lost $2.8 million last year.”

He and Borek say there are plenty of stories lately about growers losing their farms. They declined to provide dollar-and-cents figures or names.

There’s also a question of food safety. Local food supports are quick to point out that only 2 percent of fruits and veggies that come into the U.S. from elsewhere are inspected by U.S. agriculture experts.

“It’s important for people to ask for local products, Florida products, U.S. products. You want to support the people who contribute to your community,” LaPradd said.

Follow @Cveiga on Twitter.