DETROIT, MICH. — As the economy falters, another war lurches into chaos, and our nation’s gravest environmental calamity plays out in slow motion at the rate of at least one Exxon Valdez spill per week in the Gulf, a kind of sour despair has taken root in progressive circles.

“Where is the left?,” David Roberts asked in a plaintive recent essay. The question is a fair one. Where are the protests, the convulsions of dissatisfaction and outrage, the polemics, the visions of something different and better? So far, at least in media coverage, popular outrage has been monopolized by the far right Tea Party, who prescribe a whopping dose of more of the same — deregulation, tax cuts, “drill, baby, drill” — to cure what ails us.

Well, I think I might have found the left: in plain sight on the streets of Detroit, a kind of sacrifice zone for 30 years of deindustrialization and suburbanization. Detroit is the current site of the second U.S. Social Forum, a convergence of social movements from around the country rallying around the undeniable premise that “another world is possible [and] another U.S. is necessary.”

The idea of “social forums” grew out of the movement against corporate-led globalization that gained force at the WTO protest in Seattle a decade ago. Rather than gather merely to react to intergovernmental policy that props up vast, transnational global companies answerable only to their shareholders, why not get together to germinate and discuss alternatives as well? World Social Forums have been convened since then in Mexico and India; the first U.S. Social Forum happened in Atlanta in the summer of 2007.

The expected crowd for this week’s events is at least 30,000 strong. On Tuesday, untold thousands of people marched down Detroit’s storied Woodward Ave — the city’s main transport thoroughfare, running the length of Detroit and dividing the city into east and west. A bustling streetcar once carried the city’s working-class population to its car factories along Woodward. First the streetcar vanished, then the car factories, and now Woodward Avenue belongs exclusively to cars made elsewhere.