Medellín's Green Corridors (Corredores Verdes) — 30 Planted Corridors and a Reported 2°C Cooling, Awaiting Rigorous Evaluation

Medellín's Corredores Verdes programme, launched in 2016, planted green corridors along roads and waterways to counter the urban heat island and improve air quality. The city reports 30 corridors, around 2.5 million plants and 880,000 trees by 2021, at a cost of about USD 16.3 million. The project won a 2019 cooling award from the charity Ashden, and a gardener-training component trained 75 new gardeners drawn from vulnerable or displaced people.
The headline result is cooling. The mayor and several outlets report a drop of about 2°C in the first three years of the programme, and a secondary analysis cites average air temperatures at corridor sites falling from 31.6°C to 27.1°C between 2016 and 2019. These are before-and-after comparisons at corridor locations or city-reported averages; they are not controlled studies and do not separate the programme from wider weather trends.
UCL's Bartlett Institute describes the early signs as positive but stresses that robust evaluations, along with continued upkeep, will be vital. The programme is therefore best read as a promising, well-documented intervention with an evidence gap, not a proven one.
Its strengths are scale, low per-corridor cost, a visible social element (paid gardener jobs for vulnerable residents) and clear transferability to other hot cities. Open questions are maintenance funding, water use and whether cooling benefits reach the hotter, poorer hillside neighbourhoods.

Read the full analysis: https://preventionweb.net/quick/65508