Zalcoatitán, the valley where the city of San Salvador is located, was named “de Las Hamacas” (of the hammocks) by Spanish conquistadors centuries ago due to the frequent seismic activity in the area, which creates a sensation of ‘swaying.’ The city is also the capital of El Salvador, a small Central American country with a population of just over 6 million, nearly a third of whom live in the metropolitan area.

In addition to the ‘hammocks,’ the Salvadoran capital experiences 22 days a year with temperatures above 33°C, has limited urban public space (less than 5% of the total), and a continuously growing automobile fleet. Adding to this, it is the third most densely populated city in Central America, making the urban heat island effect a major local challenge. The high temperatures, which can be up to 2°C higher than in nearby rural areas, have a greater impact on the quality of life of the most vulnerable residents. Access to cooling mechanisms such as air conditioning can be a luxury, and the already limited public space becomes even less accessible for leisure and social interactions.

When the Inter-American Development Bank (IDB) Cities Lab launched the Cities for All Challenge a couple of years ago to experiment with innovative urban solutions, San Salvador didn’t hesitate. Its Metropolitan Area Mayors’ Council (COAMSS-OPAMSS), together with Don Bosco University and local organizations specializing in green infrastructure, submitted a proposal to mitigate the urban heat island effect, which was selected as one of the three winners. The project, titled “San Salvador in Development… of Overheating?”, proposes installing green roofs and walls in buildings and public spaces to reduce surface temperatures, improve air quality, and provide shade in key areas. The pilot aims to experiment with different materials, plant species, and substrates best adapted to local conditions—selected with the help of experts from the Botanical Garden—to determine the most effective bioclimatic and cost-benefit solutions. Another key objective is training municipal teams in the installation and maintenance of green modules and documenting the lessons learned in a manual including criteria and recommendations to be integrated into city regulations in both the pilot municipalities and beyond.

So far, data collection has assessed the impact of vegetation on temperature reduction, showing differences of up to 11°C compared to uncovered surfaces. These initial results suggest that the strategy is both viable and replicable, paving the way for its expansion in the city. Next steps include evaluating its long-term sustainability and effectively integrating these modules into urban planning regulations. For updates on the project: https://www.udb.edu.sv/san_salvador_en_desarrollo/allnews.php.