It would be interesting to see which other U.S. cities could draw as big a crowd as the one at the 9th annual San Francisco Green Festival last weekend. The expansive Concourse Exhibition center was packed with the usual suspects and more: the generous smattering of hippies in dreadlocks and flowing organic cotton fashions was only part of the varied crowd, which seemed to encompass all the demographics you’d normally find around town.

While this festival is partly a showcase and marketplace for just about any green product you can think of — from jewelry, clothing, and towels to food and drinks to the latest electric cars — and may therefore seem less serious than the more businesslike green conferences in the Bay Area, it serves an important function in getting so many people involved and engaged. There’s a lot to be said for making green more mainstream. And in between shopping, you can also choose among talks on a wide range of subjects. The ones I attended exemplified the energy and message of the festival, and the theme of personal and global engagement.

There’s an urgency to environmentalism today that can’t be denied. As Bill McKibben of 350.org reminded his audience, climate change is happening faster than we’d thought — and while we have the technology to solve many of our problems, the political will isn’t as easy to come by. John Perkins, author of Hoodwinked, pointed out that this is the first time in history that the whole world is confronting the same crisis. But it’s also the first time that we’re all communicating with one another, in a way that wasn’t possible even a few years ago. As an illustration of this, 350.org has more than once virtually gathered people from all around the world — their Global Day of Action was called “the most widespread day of political action in the planet’s history,” and this year their Global Work Party drew people to 7,347 events in 188 countries.

We all have tremendous power to make changes. If you don’t believe that, just look at the many examples of people who have helped change the world. Rallies organized by 350.org’s predecessor in 2007 helped convince political leaders to set a goal of cutting carbon 80% by 2050. In Florida, as Perkins recounted, the head of an environmental agency had the courage to take a stand against a coal-powered plant, and the people stood behind her. The coal company got the message and is now the largest wind and solar company in the U.S. While they used to spend millions against CO2 taxes, now they fight for them — because the people spoke.

So what can you do? It depends what your passion is; it’s up to all of us to get involved in any way we can and do whatever makes the most sense for us. Connect with others who are trying to do the same things; volunteer to install solar panels; join organizations that force corporations and governments to change. It took just a few people to convince the administration to put solar panels back on the White House; imagine what we can do with many more of us. If we all engage in activities like this and make our voices heard, change will happen. And events like the Green Festival, which bring so many green-minded people together, can help facilitate that and inspire us all to keep pursuing our goals.