After enduring years of high crime and violence, Medellín faces a new threat –  rising urban temperatures, driven by climate change. The city’s response brings people together, planting vegetation to create a better environment for everyone. 

The Green Corridors project shades cyclists and pedestrians, cools built up areas and cleans the air along busy roads. The city's botanical gardens train people from disadvantaged backgrounds to become city gardeners and planting technicians. Temperatures have fallen by two or three degrees Celsius in places, with bigger reductions expected  in the future.

The programme came from the need to connect people to nature – recovering spaces that were occupied by concrete

Sergio Orozco, Secretary of Environment, Alcaldía de Medellín

As global temperatures climb higher, our daily lives are becoming more uncomfortable and even dangerous, with heat waves a deadly threat. In cities, the problem is made worse by the urban heat island effect, where large areas of concrete and tarmac absorb the sun's heat, pushing temperatures up even further. 

Colombia’s second largest city, Medellín, has introduced an exciting urban greening programme called Green Corridors. The programme is boosting biodiversity and reducing the urban heat island effect. Through beautiful and functional greenery, the city is adapting to climate change and giving residents a better quality of life.

Medellín’s city authorities have improve the environment of the city by creating green corridors – areas thick with vegetation – along 18 roads and 12 waterways. The project aims to create a more beautiful city, tackle the urban heat island effect, increase biodiversity and cut air pollution. Cooling is created by more shading, cuts to the heat radiated by solid surfaces such as a roads, and water evaporating from plants.

Since the programme started the botanical gardens have trained 75 new gardeners. This has helped people who are most vulnerable, displaced by the armed conflict or from poorer rural communities to find work. The apprenticeship scheme gives them workplace training as well as a qualification. 

The programme has improved and created 65 hectares of planting in the city’s waterways and 6.2 hectares on its roads. 2 hectares of paved ground have been turned into planted areas.

8,300 trees and palms (comprising 72 carefully selected species) have been planted so far, along with 353,765 shrubs. The selection of species was carried out with the help of the Botanical Garden of Medellín. Trees were selected to provide food for wildlife and create a network of greenery that birds, mammals and insects can use to travel around the city.

Each corridor is designed specifically to mimic a natural forest situation. This means there are low, medium and high plants to encourage animals and insects. Taller trees have been planted that will, when fully grown, provide the maximum amount of shading and cooling.

One million people cross through Medellin’s downtown every day for work, study or tourism. The scheme’s highlights include the Oriental Avenue, a main road where 2.3 km of paving was replaced by gardens. Another is La Hueso Green Corridor, along a road and cycle route following the above-ground Metro line and river into the city.

The Metro line was constructed 24 years ago and the area under the raised track was underused. Now the city collects rainwater from the bridge, filtering it down through a system of pipes to water the greenery (which includes ‘green walls’ planted with vegetation). This green corridor helps to reduce the temperature along a popular cycling route.