Green Corridors and Heat Chiefs: How Cities Are Fighting Extreme Temperatures

As Western Europe swelters through a record-breaking May heatwave — with temperatures reaching 39°C in parts of France and new May records set in the UK — Belgian cities are increasingly becoming “pressure cookers” in summer, as De Morgen recently reported. But from Athens to Medellín, urban planners are pioneering innovative strategies to keep cities livable as the climate warms.

The Urban Heat Island Problem

Cities are typically 4 to 10°C warmer than surrounding rural areas — a phenomenon known as the urban heat island effect. Dark materials like asphalt and concrete absorb and re-radiate heat, tall buildings trap warm air and block circulation, and the lack of vegetation eliminates natural cooling through evapotranspiration. According to Euronews, EU research found that higher city temperatures due to this effect were associated with 6,700 premature deaths in summer 2015 alone. With around 75% of Europeans living in urban areas, the stakes are high.

Athens: The Rise of the ‘Heat Chief’

In 2021, Athens became the first European city to appoint a dedicated Chief Heat Officer (CHO) — Eleni Myrivili — a role pioneered by the Adrienne Arsht-Rockefeller Foundation Resilience Center. “Such an appointment may seem symbolic, but it is not,” Maarten Van Acker, an urban planner at the University of Antwerp, told De Morgen. “It is fundamental. A city decides that heat is not a seasonal phenomenon after which we return to business as usual, but a health and safety issue that requires permanent policy attention.”

Myrivili’s achievements include developing an algorithm that predicts the impact of heatwaves on Athens and alerts vulnerable populations. The CHO coordinates across government agencies, working with cooling maps, heat protocols, and early warning systems to make public spaces cooler.

Medellín: Green Corridors That Cool by Degrees

Perhaps the most celebrated example comes from Medellín, Colombia. Between 2016 and 2019, the city created approximately 30 green corridors — networks of trees and plants stretching 20 kilometers along roads, cycle paths, and pedestrian routes. With 880,000 trees and 2.5 million smaller plants, these corridors form a green network that provides permanent shaded passageways across the city.

The results are striking. In 2010, Medellín was about 6°C hotter than its surrounding rural areas on hot days. That difference has already dropped to 4°C, and the city expects to eliminate the urban heat island effect entirely by 2050. Cities including Bogotá, London, Mexico City, and São Paulo are now following Medellín’s example.

Hong Kong: Designing for the Wind

Hong Kong, one of the most densely populated places on Earth, takes a different approach: harnessing the cooling power of wind. The city requires developers to conduct “air ventilation assessments” before building new neighborhoods, ensuring that “breezeways” allow fresh wind to penetrate deep into the urban fabric.

“Streets in Hong Kong are laid out in the direction of the wind, so that fresh air can reach deep into the city,” Van Acker explained. “This creates open boulevards that function as a cooling system. It’s almost the opposite of how we do things here.” He noted that in Flanders, wind is typically blocked rather than channeled, with new developments studied only from a comfort perspective — asking whether it will create too much of a draft rather than how it might cool the city.

Munich: The River as a Cooling Lifeline

Water, too, plays a critical role. Twenty-six years ago — well before European summers became a succession of heat records — Munich launched a major renovation of the Isar River, investing €38 million to clean the water, expand floodplains, and adapt the riverbanks. Originally designed for flood protection and ecological restoration, the revitalized river has become an essential cooling refuge during heatwaves.

“I visited the banks of the Isar with my students,” Van Acker said. “The banks are completely greened and lowered, with pebble beaches where everyone can swim and even surf in the middle of the city. During heatwaves, the river has truly become a cool lung accessible to everyone.”

What This Means for Belgian Cities

The article by Barbara Debusschere in De Morgen comes amid growing pressure on Belgian cities to act. In Antwerp, opposition party Groen has criticized the city for lacking a comprehensive heat plan, despite approving a ‘Groenplan’ in 2017 that aimed to create green corridors. The city government points to its Klimaatplan 2030 and the 3-30-300 rule — ensuring three trees visible from every home, 30% canopy cover, and 300 meters to green space.

Van Acker emphasized that cities need interventions at all levels. “A beautiful example of a local measure is the Claes de Vrieselaan in Rotterdam,” he said. “Parking spaces there were partially depaved, making it 10 degrees cooler.”

The Road Ahead

As climate scientists like Friederike Otto of Imperial College London note that this May’s record-breaking heat “has the fingerprints of climate change all over it,” the urgency for urban adaptation has never been clearer. The four world cities profiled in De Morgen’s report demonstrate that effective solutions exist — from high-level coordination through Chief Heat Officers to grassroots depaving projects. The challenge now is scaling these innovations to cities worldwide, before the next heatwave arrives.