What makes a city the greenest of the green? There are thousands of cities and towns of all sizes around the world that have instituted impressive recycling programs, planted vast tracts of protected green space and promoted the use of resource-conserving technologies. But among global green cities, the ones that stand out are the ones actively fighting climate change on a large scale, and setting an example for the rest of the world.


These 10 cities are among the world's greenest, encompassing all of the positive qualities that make urban living  more healthy, pleasant and sensitive to nearby ecosystems. They were chosen based on their use of renewable energy, high concentrations of clean-tech companies, promotion of green lifestyles, laws that protect the environment and innovative strategies for new green communities.


1. Reykjavik, Iceland

For an example of a sizable city that manages to run almost entirely on clean, renewable energy, the rest of the world need look no further than Reykjavik. The city has capitalized on its natural abundance of volcanoes and geothermal energy, with only 0.1 percent of its electricity coming from fossil fuels. The city's buses run on zero-emission hydrogen power for one of the greenest public transit systems in the world.


2. San Francisco, Calif.

San Francisco and Portland, Ore., tend to be deadlocked for the title of America's greenest city, but when it comes to measured impacts, the former seems to win out. San Francisco came in the top three greenest cities of North America in five out of nine metrics ranked by the Economic Intelligence Unit in 2011 including energy, green buildings, transportation, water and air quality. The city is renowned for passing tough laws that reduce waste and emissions, like banning plastic shopping bags and making recycling a requirement.


3. Malmö, Sweden

Sweden's third-largest city is a model of urban sustainability, leading in renewable energy solutions and abundant green space. The city is home to the third-largest wind energy park in the world and aims for all of its city operations to be climate-neutral by 2020. Designated as Sweden's first Fair Trade city in 2006, Malmö's success as a sustainable city is a result of careful urban planning that has been carried out over decades.


4. Vancouver, Canada

Already the greenest city in Canada and the second-greenest in North America after San Francisco, Vancouver is well on its way of achieving its goal to become the greenest city in the world by 2020. The city is a hub for clean-tech innovation, boasts low-carbon emissions and draws an impressive 90 percent of its power from renewable sources, mostly in the form of hydroelectric power. Vancouver also has more than 200 parks. Vancouver has the greenest new neighborhood in America and diverts 55 percent of its regional solid waste from the landfill.


5. Portland, Ore.

The first city in America to adopt a climate action plan, Portland has more LEED-certified residential towers than any other city in the nation, and its land use laws ensure that the city stays dense while suburban and rural land is preserved for agricultural purposes. A quarter of its workforce relies on public transportation, carpooling or bicycles to commute each day, and the city offers free plug-in parking spots for electric vehicles.


6. Curitiba, Brazil

Curitiba is the undisputed green capital of Brazil and was ranked by Siemens as Latin America's greenest metropolis. The city has 16 parks, 14 forests and more than 1,000 green public spaces, and its environmental legislation protects local vegetation that is threatened by urban development. Seventy percent of its waste is recycled and the city has planted 1.5 million trees along its highways and byways. A flock of sheep even roam the parks to keep the grass clipped.


7. Copenhagen, Denmark

Nearly one-third of Copenhagen residents primarily rely on a bicycle for everyday commuting, and visitors to the city will find that bikes are a pervasive presence. Even with these high rates, the city is working to increase bicycle ridership by 50 percent by 2015. The coast of Copenhagen is dotted with wind turbines and the city is known as a worldwide leader in its efforts to combat climate change.


8. Stockholm, Sweden

Long listed among Europe's most environmentally conscious cities, Stockholm won the 2010 European Green Capital for its commitment to sustainability. Forty percent of the city is composed of green spaces, and the city invests heavily in environmental protection. Efforts to clean the city's abundant waterways began in the 1960s and today, salmon caught even in the urban areas of the river are edible. Stockholm's carbon emissions are just 3.4 tons per capita, far below the European average of 10 tons.


9. Hamburg, Germany

Winner of the 2011 European Green Capital designation, Hamburg is redeveloping much of its urban core to align with sustainability principles. For example, its new HafenCity Hamburg is Europe's largest city development project with 388 acres of rehabilitated former industrial land that is now full of housing, shops, parks, entertainment and other amenities. As one of Europe's busiest industrial ports, Hamburg is making big plans to green its operations; the city plans to use 'container taxis' that will each displace 60 trucks to reduce pollution.


10. Bogotá, Colombia

The capital city of Colombia has much improved its reputation in recent years, from one of organized crime and poverty to one of a promising green future. Rated by Siemens as one of Latin America's greenest cities with above-average environmental stats, Bogotá has an efficient public transit system, hundreds of miles of bike trails and more than 1,200 urban green spaces. The city drastically improved its air quality, water supplies and urban trees and deceased its wildlife trafficking over a four-year period between 2008 and 2011.


Know of other global green cities? Leave us a note in the comments below.


MNN tease photos of Reykjavik and city illustration: Shutterstock


Global green cities
These 10 cities are among the world's greenest, encompassing all of the positive qualities that make urban living much more healthy, pleasant and sensitive to n