Europe did it this summer, and so did Israel.
But just because cities are regularly ranked based on how environmentally friendly they are, that doesn't mean the chosen cities are always quite as green as they may seem.
Environmental experts say that while some of these cities make it on to the good list because of their parks and public transportation, their residents' high standard of living means they continue to exploit and consume a great deal of resources and create a lot of waste.
The top three picks in a June ranking of sustainable cities in Israel were Tel Aviv, Kfar Sava and Jerusalem.
The rankings are based on 10 standards, including fostering open spaces, reducing waste and having environmentally friendly and accessible transportation. The index was compiled by the Heschel Center for Environmental Learning and Leadership and Life and Environment, an umbrella group representing more than 100 Israeli environmental groups.
But while Tel Aviv led the list thanks to its parks and bike lanes, the city does not do well on recycling. Kfar Sava earned points for its recycling as well as its support for energy-efficient buildings, but its residents say the city is not keeping them informed about environmental issues and has not protected its old-growth trees.
And though Jerusalem is building more parks, has a light-rail system and is planning to implement ambitious proposals to reduce air pollution, in recent years the capital has been moving most of its garbage to an old, polluting landfill in Abu Dis. In addition, the environmental group Tzalul has ranked Jerusalem the second-worst city when it comes to damaging water sources, saying its continued channeling of untreated waste into the Kidron Valley is damaging the unique desert landscapes east of the city.
In Oregon, the city considered one of America's greenest is Portland, 8 percent of whose energy comes from renewable sources. But in a recent article in the scientific journal PLOS Biology, a group of experts wrote that while Portland is indeed a pleasant place to live, with its parks, bike routes, organic markets and recycling, the city is utterly dependent on nature's resources.
"Each year the Portland metropolitan area consumes at least 1.25 billion liters of gasoline, 28.8 billion megajoules of natural gas, 31.1 billion megajoules of electricity, 136 billion liters of water, and 0.5 million tons of food, and the city releases 8.5 million tons of carbon as CO2, 99 billion liters of liquid sewage, and 1 million tons of solid waste into the environment," the article states. "Total domestic and international trade amounts to 24 million tonnes of materials annually. With respect to these flows, Portland is not conspicuously green."
European environmental agencies also note the broader implications of urban lifestyles. According to some estimates, the ecological footprint of London, for example, affects an area 300 times as large as the city itself.
Some of the world's cities are trying to take a different direction and go for reduced consumption.
One of these is Frankfurt, which has reduced the overall amount of garbage its residents generate and has prohibited the use of wood coming from tropical species of trees.
Copenhagen, the recently announced winner of the competition for European Green Capital of 2014, is also heading in that direction by recycling 90 percent of its construction materials, thus reducing its dependence on newly produced materials that take more resources from nature.
In addition, Copenhagen incinerates most of its trash and the energy produced in that process is used to heat homes. The city has also begun using home water-use gauges (also in use in Israel ) that have led to a water-use decline of 25 percent.
The Danish capital beat out the German and British entries, Frankfurt and Bristol, largely because of the significant rise of bicyclists in Copenhagen as a result of urban planning decisions intended to reach that goal.
One-third of the city's 2 million residents now bike to work or school, and Copenhagen plans to raise that proportion to a full half the population within four years. The city has also built several new parks as part of its goal to have every resident living within a 15-minute walk of a park or beach.
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