For most of our history, human settlements have lived in rural, low-density environments. However, 2007 was the year in which the urban population exceeded the rural one for the first time — and the world’s urbanization continues at a dizzying pace.

Currently, over 4.3 billion people live in urban areas. Due to the ongoing urbanization and global population boom, the numbers are only accelerating: By 2050, seven out of 10 people from the predicted population of 10 billion will live in cities.

Even though cities cover only 3 percent of the earth’s surface, they host more than half of its population and produce about three-quarters of global carbon emissions.

While these figures might sound dire given the harsh implications of climate change, there’s also a silver lining: Due to their sheer size and influence, any green measure in cities can have a massive impact and inspire others to follow the course.

Hereafter are five cities on five different continents that have already implemented some measures, determined by their unique needs and resources.

Basel, Switzerland: Where Green Roofs Are Mandated

In Basel, since 2002, every new and retrofitted building must have a green roof, which has a myriad of benefits for urban life.

In Basel and beyond, green roofs reduce energy bills, risks of flooding, and noise levels. They can store rainwater for daily use while improving local biodiversity and air quality.

Even though the green roofs are taking over the world and becoming a more ubiquitous sight in many other cities, Basel was the first city in history to make green spaces a legal requirement in buildings, inspiring other European cities to do the same.

Medellin, Colombia: Where Green Corridors Improve Air Quality

Following decades of progress and development, Medellin, once known as one of the most dangerous cities in the world, is now striving to earn a different kind of reputation: An eco-friendly city.

In 2016, the city started its “green corridors” project, an interconnected network of greenery across the city which has already reduced Medellin’s temperature by 2°C and significantly slashed the air pollution levels.

The project hired 75 residents from disadvantaged backgrounds to further tackle poverty and sustainable growth issues in the city.

Vientiane, Laos: Using Nature to Keep the Floods Out

The landlocked and mountainous Laos is among the most vulnerable countries to flooding and drought risks. With support from the Green Climate Fund, the Southeast Asian nation is now tapping into natural ways to mitigate these risks.

A new five-year project in the capital Vientiane, and three other Laotian cities, is restoring urban wetland and stream ecosystems to regulate water flow and reduce flood risk.

This shift from hard infrastructure toward nature-based solutions is cost-effective and expected to benefit about ten percent of the country’s 7.2 million people.

Washington DC, USA: Sustainable Food for All

Washington DC, which is already one of the most sustainable cities in North America, now has an initiative, RiverSmart, to gain even more green stars.

RiverSmart program provides financial incentives to local property owners to embrace green infrastructure, including green roofs, rain gardens or barrels, and more, helping the ground to soak the rainwater.

This initiative further empowers non-profits, businesses such as hotels and restaurants, schools, or individual residents to run community farms and gardens. This way, an increasing number of Washington DC residents now have access to fresh, locally sourced, and healthy food.

Melbourne, Australia: Combating the Heat Island Effect

The Australian city of Melbourne is among the many to suffer from the “Urban Heat Island Effect“, which occurs when dense concentrations of the built environment that can retain heat replace the natural land cover.

To counter it, the city is creating five new regional parks and four new conservation reserves in its metropolitan area, more than tripling the number of green areas as such.

These new projects are set to not only cool down the city but also increase the life quality for its residents.