Medellín City Council - Green Corridors that cools the city

Medellín, Colombia · 2016 · Alcaldía de Medellín, through its Secretaría de Medio Ambiente, with the Joaquín Antonio Uribe Botanical Garden as technical partner

The programme reversed the warming trend recorded in previous years, measurably cooling the city and improving air quality along heavily trafficked corridors such as Avenida Oriental, where paving was replaced by gardens. It expanded and connected urban habitat, supporting the return of biodiversity, and greened metro stations, bridges and public buildings. Socially, it trained and employed residents from vulnerable and displaced backgrounds as urban gardeners, and its selection through Participatory Budgeting built durable public support. Internationally it earned recognition including the Ashden Award for Cooling by Nature and a C40 Bloomberg Philanthropies Award, positioning Medellín as a reference model. A documented trade-off is the debate over “green gentrification”, where public-space upgrades may raise land values and pressure low-income residents.

Highlight

A low-tech, nature-based network of 30 green corridors that cut Medellín’s temperature by 2°C while creating jobs for vulnerable residents.

Extended description

Context and problem. Years of rapid urban expansion left Medellín — Colombia’s second-largest city — with less vegetation and more concrete and asphalt, producing a strong urban heat-island effect that pushed city temperatures above those of surrounding areas and worsened air quality. City authorities recognised the need to reverse this loss of green space.
How the solution works. Beginning in 2016, the city built a connected network of 30 green corridors along major roads and waterways, linking parks, squares, roadside verges, pavements, vertical gardens and several of the hills surrounding the city. Each corridor is designed to mimic a natural forest, combining low-, medium- and high-level vegetation — native and tropical plants, bamboo grasses, palms and trees — to maximise shade, cooling and habitat. Heat-trapping infrastructure such as metro stations and bridges was greened, and public buildings received green roofs and vertical gardens; the flagship living wall at City Hall spans about 1,810 m².
Technologies and processes. The approach is predominantly a low-tech nature-based solution (NbS), relying on large-scale tree and plant establishment, but it is guided by bioclimatic studies and careful species selection, and framed within the city’s wider “smart/greener city” strategy. Cooling is achieved through shading, reduced heat radiation from hard surfaces, and evapotranspiration, which releases water vapour and lowers the temperature; the vegetation also captures particulate matter.
Operational logic and stakeholders. The Secretaría de Medio Ambiente (Environment Secretariat) led the programme; the Joaquín Antonio Uribe Botanical Garden trained gardeners and provided botanical expertise. Citizens selected and prioritised the project through Medellín’s Participatory Budgeting process, giving it strong social legitimacy. Maintenance is carried out by teams of citizen-gardeners recruited from disadvantaged and displaced communities, supported by forestry engineers.
Systemic implications. By converting streets and grey infrastructure into a connected ecological network, the project treats urban greenery as climate-adaptation infrastructure rather than decoration. It couples environmental gains (cooling, air quality, biodiversity) with social inclusion (green jobs for vulnerable groups), and has become an internationally recognised, highly replicable model for heat-stressed cities.

Demonstrated metrics

Temperature: local average temperature reduced by ~2°C within the first three years; further cooling of 4–5°C projected over the coming decades.
Network: 30 interconnected corridors (18 along roads, 12 along waterways); more than 70 hectares of green space, including ~20 km of shaded cycle/pedestrian routes.
Planting: ~120,000 plants and 12,500 trees at launch, reaching ~2.5 million plants and ~880,000 trees by 2021.
CO₂: a C40 study estimated ~160,000 kg of CO₂ absorbed per year by vegetation in a single corridor in the initial phase.
Air quality: capture of fine particulate matter (PM2.5); reported PM2.5 reduction of ~8% (2016–2019).

Real impact

The programme reversed the warming trend recorded in previous years, measurably cooling the city and improving air quality along heavily trafficked corridors such as Avenida Oriental, where paving was replaced by gardens. It expanded and connected urban habitats, supporting the return of biodiversity, and greened metro stations, bridges and public buildings. Socially, it trained and employed residents from vulnerable and displaced backgrounds as urban gardeners, and its selection through Participatory Budgeting built durable public support. Internationally, it earned recognition, including the Ashden Award for Cooling by Nature and a C40 Bloomberg Philanthropies Award, positioning Medellín as a reference model. A documented risk is “green gentrification”, in which public-space upgrades may raise land values and put pressure on low-income residents.

Cost of the solution

According to media reports, the establishment cost was approximately US$16.3 million — a modest amount at city scale, equivalent to roughly US$6.50 per resident — with annual maintenance costs of approximately US$625,000.

Implementation location & date

Medellín, Colombia. Operational programme launched in 2016 (main build-out 2016–2019), with maintenance and expansion ongoing. Priority areas include Avenida Oriental and other high-pollution, high-traffic corridors.