Last week, mayors from across the world met at the Fourth Annual C40 Mayors Summit. They shared lessons learned and best practices and discussed the role of cities as potential leaders in mitigating global climate change.

One mayor, Sam Adams of Portland, Oregon, shares his vision for change:

In the United States, Portland is well known for an extensive bike network that encourages our residents to pedal whenever possible – a network we’ve honed by looking to best practices in places like Amsterdam and Copenhagen. We’re also the home of the first modern streetcar system in the U.S., modeled after streetcar lines in the Czech Republic. And we’re currently studying five pilot EcoDistricts, areas that combine elements like district energy and transportation options to create a holistic and sustainable neighborhood-similar to successful green neighborhood developments in Vancouver, BC and Malmo, Sweden.

As you can see, some of our best ideas have come from other cities. We borrow these best ideas, take them home, and try to perfect them in the context of Portland. Based on our successes, we know better than anyone else the value of learning from one another and building on each others’ best practices.

We’re also crafting our own best practices to share with the world. We’ve positioned Portland as a living laboratory, where we pioneer new green technologies, and attract and grow many companies who want to experiment, innovate, and create bold prototype projects. The Oregon Sustainability Center is one example. When built, it will be the largest triple-net zero office building in the world, and it has attracted partnerships from companies such as Skanska, GE, and Sanyo Solar. It is also promoting the work of Portland-based green companies such as Gerding Edlen and SERA Architects.

We’re also launching the Green Innovation Park. One city block will be transformed into an experimental expo for new green building and energy conservation products. We are partnered with the British firm BRE, which is doing similar work in Brasilia.

And we’ve created programs that help our citizens who want to increase their energy efficiency, in an affordable way. The first, Clean Energy Works Oregon, offers no-money-down, easy financing for home energy efficiency improvements, which homeowners pay back on their utility bill. Partnerships with local banks and utilities provide the capital needed to finance these residential upgrades. The second, Solarize Portland, is a partnership with neighborhoods to buy and install solar electric panels in bulk. This saves homeowners money, and ensures that hundreds-if not thousands-of Portland homes are powered by a clean energy source.

In Portland, we develop these projects and programs in our living laboratory for the benefit of our own citizens. Then we offer our solutions up to the world, in the spirit of open source collaboration.

First Stop Portland-an organization based out of Portland State University-is one way we roll out our city’s welcome mat, to connect visitors from around the world with business, political, and research innovators who are well versed in Portland’s best practices, because they’ve created them.

We also created the Portland Sustainability Institute, an organization that drives projects like our pilot EcoDistricts, and shares their insights via an annual EcoDistricts Summit. The Summit brings together leading municipalities, businesses, professionals, nonprofits and academics from around the world, to collaborate on neighborhood-scale innovation.

We’ve even shared our city’s 2009 Climate Action Plan-our strategy to reduce carbon emissions 80 percent below 1990 levels by 2050-with China: USAID recently translated the Climate Action Plan into Chinese to help guide the development of “low carbon cities” in China.

To succeed in our fight against climate change, cities have to be practical, innovative, and collaborative. In Portland, we hope that sharing what we’ve learned will help other cities reach even higher. We want others to take our ideas home and perfect them. Working together, we can avoid reinventing the wheel-and can instead improve upon solutions that have already been ground tested and are already making a difference.

Sam Adams is the mayor of Portland, Oregon, a member of the C40 Cities – Climate Leadership Group.

Picture: Bike commuters travel down along a street Thursday, May 12, 2011, in Portland, Oregon.