The battle against blight has been waged by city officials around the nation for the last several decades. Vacant homes and decrepit properties can be magnets for crime, and they can devalue the neighborhoods around them.

St. Petersburg, Fla., may have come up with an innovative way to address blight, one that merges the power of the courts with the private sector.

In 2014, the city became the first in Florida to use the judicial system to wrestle neglected properties away from their owners. Because the properties, which numbered nearly 800 across the city, owed a combined $4 million in liens and unpaid assesments, the city had legal standing to file lawsuits against the owners and move the properties into foreclosure. In most cases, the properties had essentially been abandoned by absentee owners, what are commonly called "zombie properties."

Here's how the process works: Through foreclosure, the city will take ownership of a property and either sell them to nonprofit affordable housing developers for $4,000 or move them to auction. Most of the homes are then rehabbed instead of being torn down, which is one of the city's goals. The vacant land is developed as affordable housing.

“It’s really hard for a developer to build affordable housing because of the cost of the land,” St. Petersburg Mayor Rick Kriseman says. “But our program makes the land cheap enough for a developer to be able to build affordable housing.” (The city doesn't require developers to make the housing affordable.)

The city has cut the number of boarded and vacant homes by more than three-quarters since the program was launched less than four years ago.

St. Petersburg was hit especially hard by the housing market collapse in 2008, leaving many of the homes abandoned. But vacant properties are a common problem in cities, especially in the Rust Belt and Midwest. According to a report from the Lincoln Institute of Land Policy, more than 50 percent of the census tracts in Gary, Ind.; Flint, Mich.; and Detroit have at least 10 percent home vacancy rates, a condition known as hypervacancy. In Baltimore, Cleveland and St. Louis, more than 30 percent of the census tracts were hypervacant. All those empty homes cost cities money to police and clean -- not to mention the revenue lost to unpaid property taxes.

Cleveland and Detroit have adopted aggressive demolition policies, using money from the federal government's Hardest Hit Fund to reduce vacant homes to rubble and turn them into green spaces and community gardens.

Baltimore, where the population has dropped by more than a third in the past 60 years, has spent decades trying to fill vacant homes. Earlier efforts, in which the city acted as a buyer and seller of real estate, didn't see much success. But Baltimore's more recent Vacants to Value program, in which buyers have to prove they can afford to fix up their new home, has shown promise.

What's unique about St. Petersburg's effort is that it specifically targets abandoned homes and vacant lots owned by absentee landlords and is focused on turning those properties into affordable homes for lower-income residents. The initiative has cost the city $750,000 while generating $2.1 million in revenue in liens and assessments collected at auction.

Worried about real estate speculators acquiring properties just to sit on them -- and becoming absentee landlords themselves -- the city has also begun buying some of the homes directly. “We started to acquire properties at auction ourselves,” Kriseman says. “It gives us the opportunity to make sure those properties remain affordable.” The city currently owns 11 properties acquired this way, which it leases to nonprofits to construct new, affordable homes.

Kriseman, an active cyclist, spends his weekends biking the city's neighborhoods and network of trails. It's those rides that initially made him aware of just how bad St. Petersburg's blight problem had become. Now, four years later, those same routes take him through neighborhoods that are noticeably improving.

“You can visually see it,” Kriseman says about the slow transformation. “When one neighbor starts to fix up their house, it starts to spread.”