It was 10 years ago that the first yellow-clad ambassadors from the Downtown Improvement District appeared on the streets of Minneapolis. Now, it would be hard to imagine those same streets without them, and without the work they do.

Cleaner, greener, safer, livelier, more welcoming to visitors. Those words best describe the ambitions of the improvement district, known as the DID. Begun in July 2009, the DID is a public-private collaboration paid for by extra property taxes levied on businesses within a 120-block zone of the city’s core.

Hundreds of similar partnerships have arisen across the country in recent years as older downtowns struggle to remain relevant in the face of mass retail departures, persistent challenges to public safety and civility, crumbling infrastructure, and, paradoxically, booming, often affluent residential populations with expectations beyond the reach of many city budgets.

Such was the case in Minneapolis where civic and business leaders saw clearly the benefit of trying to keep an attractive, competitive metro center despite the ambivalence of neighborhood constituencies. The results after 10 years, while not perfect, leave the city core in far better relative condition.

Streets are cleaner than they would have been otherwise, thanks to frequent power-washing and trash removal. Since 2009, DID ambassadors have collected 316,000 loads of trash, removed 51,300 graffiti tags, planted and maintained 167,000 plants and trees, and offered directions and friendly advice to more than a million pedestrian visitors. “They’ve become the face of our city,” said Steve Cramer, president and CEO of the business-led Downtown Council.

Meanwhile, DID workers help with hundreds of events, large and small, from pop-up markets and street performances to the Super Bowl and Final Four. Perhaps their most critical focus is public safety. Ambassadors provide extra sets of eyes and ears for the police, both on the streets and at the downtown precinct’s command center. Violent crime, despite spikes in 2016 and this past spring, has declined downtown over the last decade.

Despite successes, the DID faces big challenges. Homelessness and its root causes are on display daily. Livability offenses are on the upswing since the city decided in 2015 to officially tolerate (some would say encourage) panhandling, loitering, lurking and spitting as freedoms of expression and assembly. As the police retreated, the DID formed “livability teams” of social workers that try as best they can to coax troubled people off the streets toward proper services (food, shelter, mental health and drug treatment, etc.). More than 16,000 such contacts have been made since 2016, but incidents persist. The problem, Cramer explained, is that uncivil behavior no longer brings consequences. He favors a broader approach that combines enforcement with social service.

Greening is another concern. The DID planted 3,000 trees over the last three years, but survival rates are poor as the city struggles to establish the leafy canopy it wants. A tree laboratory, several demonstration projects and advice from other northern cities with more successful greening programs may help in finding a winning formula. Other frustrations — like the endless road construction projects that confound drivers and the refusal of legislators to fund adequate transit options — are out of the district’s scope.

Still, downtown Minneapolis owes much to the improvement district, given the DID’s challenges and its rather modest budget ($6.9 million this year). Corny as it seems, its greatest value might be the dedication and friendly faces of its ambassadors. They convey an important message to downtown’s workers, residents, visitors and potential investors: Somebody cares. And caring cultivates confidence, which helps explain how downtown, despite its shortcomings, landed 90 new companies over the last decade and upped its residential population by 67%.