Why Medellin is less hot than before

Climate change , of course. But also our very wrong way of building and living, which turns urban areas into real heat islands , multiplying the effect of rising temperatures. It is estimated that on average in cities, the use of materials such as cement, asphalt, bricks, plastics , determines a surplus of heat, up to 5 degrees if not more. The increase in urban temperatures has significant impacts on both the environment and public health. In addition to contributing to air pollution, this phenomenon can also cause thermal stress to inhabitants , worsening pre-existing health conditions and increasing the demand for energy for cooling.

Replanting and depaving urban soils is therefore not only a response to pollution in urban areas, but also to rising temperatures. The example of Medellin is particularly indicative in this regard and allows us to make a series of reflections on the needs and priorities we have today. With a nature-based approach and a clear political vision, Colombia's second city after the capital Bogota, famous until recently mainly for the drug cartel linked to Pablo Escobar, demonstrates how cities can address climate change with apparently elementary but powerful solutions.

How? Simply by planting trees. In large quantities. To lower the urban temperature in Medellin, 33 green corridors were created that extend for 77,000 square meters along the main and busiest arteries. In these corridors, 300,000 different plant species were planted, carefully selected also for the purpose of a recovery in terms of biodiversity , acting as attractors for local fauna and beneficial insects. The green species were chosen based on their ability to adapt to urban conditions and provide ecological benefits. Plants such as tall shade trees, shrubs for ground cover, and climbing plants for walls were used to maximize the effectiveness of the project.

Result? Thanks to this intervention, the temperature in the areas with green corridors has decreased by 3°C. The increase in vegetation has also improved air quality by reducing the levels of air pollutants such as particulate matter and nitrogen dioxide.

Air analyses conducted during the project showed a significant reduction of these pollutants in the areas covered by the green corridors. The operation was conceived and strongly desired by Mayor Federico Andrés Gutiérrez who, during his first term from 2016 to 2019, initiated the project, and in his second term continued to expand it.

The beneficial effects of the reforestation process do not stop at the issue, however essential, of the lowering of the average urban temperature . With the return of vegetation to the city, numerous animal species that had disappeared due to the heat and lack of food have also returned. Butterflies, in particular, attracted by the plants that in turn attract birds, which then attract birds of prey, creating a virtuous circle. Trees that attract bats have also been planted, thus promoting the natural dispersal of seeds.

Thanks to this project, in 2019 Medellín won the “Cooling by Nature” award , a recognition for the best global project capable of cooling urban environments and improving air quality through natural solutions. And it has demonstrated that it is possible to create cooler and healthier urban environments, paving the way for future sustainable initiatives around the world. The success of this project not only provides a model for other cities, but highlights the importance of considering ecology as an integral part of urban planning.

“It is not a difficult thing to do, it is really very easy and here we are demonstrating it. You just have to want it. If there is no political will, no project can work,” says Mayor Gutierrez.