the world's five greenest cities

When it comes to choosing the world’s five greenest cities, it’s hard to know where to start. There are so many lists out there in the ether and they all seem to have their own particular criteria as to what makes a city green.For example, TravelBird looked at the amount of green space the original 50 cities have, dividing it into three categories— natural (such as woodland), man-made (like parks and public gardens) and food production (such as orchards and vineyards).Treepedia is an interactive, map-based platform that measures tree canopy coverage in cities around the globe. Dw.com looks at cities attempting to reduce their overall carbon footprints, aimed at changing behaviour and reducing emissions.Then, of course, we need to consider other factors which have a strong bearing on how easy it is for a city to ‘green’ itself. Factors such as climate, location, economic activity and, especially, size are inevitably going to have a strong influence on the efforts a city may make to become more environmentally friendly. Nevertheless, here are some cities that seem to have a pattern of appearing in many different ‘green lists’. There’s a top-five, but also a longer list of the ‘lucky losers’, all of which can be seen as having various shades of green.

Copenhagen

The frontrunner. It aims to be the first carbon-neutral city by 2025. Copenhagen stands out for its sustainable mobility (car-free areas), good public transport and its extensive cycling network. All district heating and cooling systems are green and some even use seawater.

Reykjavik

This city is really big on renewable heat and energy, which is largely achieved through hydropower and geothermal power. Astonishingly, 95% of homes are connected to the district heating network (then again, the entire population of Iceland is only 300,000). By 2040, the country aims to make all public transport fossil-fuel-free.

Curitiba

In the eighth biggest city in Brazil, 60% of its inhabitants use public transport and it boasts 250 km of bike lanes. The green belt provides protection against flooding. But the future may be more challenging because Curitiba’s population is exploding, so it is going to take an enormous effort to ensure that greening process continues.

San Francisco

This is the only city in the USA where all new buildings must have energy-generating photovoltaic rooftops by law. The city banned plastic bags in 2007 and an urban food waste system was introduced nine years ago. San Francisco ambitiously plans to go waste-free by 2020. The majority of its buses and light railways are zero-emission.

Frankfurt

Aiming to have a 100% renewable energy supply by 2050. Certain polluting materials such as PVC are banned and its innovative waste management system has reduced non-recyclable waste enormously.It is impossible to verify that the cities above are the definitive top five, but they are all certainly implementing measurable and sustainable policies to ensure a greener future. However, we certainly shouldn't underestimate the efforts being made by the following cities:Toronto, Seattle, Amsterdam, Geneva, Sacramento, Johannesburg, Durban, Cambridge, Mass. (U.S.), Sydney, Vancouver and SingaporePerhaps one or more of these cities across the five continents will be breaking into the green top five soon.