Corredores Verdes de Medellín — Green Corridors Cooling a Colombian City

Formalised through Medellin's 2014 land-use plan (Acuerdo 048) and delivered from 2016 to 2019 under Mayor Federico Gutierrez, the Corredores Verdes (Green Corridors) programme converted 18 road medians and 12 waterway edges -- roughly 70 hectares -- into vegetated corridors, aiming to counter the city's urban heat island and reconnect fragmented green space in the Aburra Valley.

The Medellin Mayor's Office, working with the Area Metropolitana del Valle de Aburra and the municipal botanical garden, trained around 75-100 citizen gardeners and employed roughly 2,600 people across the initiative, which the 2019 Ashden Award (an independent UK-based sustainability prize) recognised for planting 8,300 trees and palms across 72 species plus roughly 350,000 shrubs.

Monitoring between 2016 and 2019 recorded average air temperatures in corridor areas falling from about 31.6C to 27.1C, with surface temperatures at some monitored hotspots dropping by up to 10C, alongside modest reductions in PM2.5 and PM10.

The programme lapsed between 2020 and 2023: Colombian newspaper El Colombiano reports that no new corridors were added and maintenance became inconsistent during this period, before the city revived and expanded the initiative from 2024, growing the network to 56 corridors (27 road-based, 29 stream-based) covering roughly 115 hectares by 2026. Cost and scale figures vary considerably between the Ashden Award's original case study and widely recirculated media aggregations (which cite up to 2.5 million plants and $16.3 million in investment) -- these larger figures could not be traced to a single authoritative municipal dataset and should be treated with caution. The 2020-2023 hiatus shows that political continuity, not just design, determines whether such programmes are sustained.