BACKGROUND

The Green Corridors project in Medellin, Colombia, aims to tackle urban environmental challenges, particularly the urban heat island effect and high levels of air pollution, which are exacerbated by heavy motorbike traffic and extensive concrete surfaces in public spaces. The project focuses on improving air quality, cooling temperatures, and enhancing the city’s green infrastructure. This initiative is part of a larger effort titled "A Greener Medellín for You," aiming to make Medellin a more attractive, sustainable, and livable city.

Figure 1 illustrates the tranformation of Medellín, from a city marked by violence and poor infrastructure in the 1990s to a modern urban center with improved public services like the Metrocable. This innovation connected marginalized hillside communities to the rest of the city, enhancing access, safety, and opportunity.

Figure 1. Early 1990s(left), Post-2010 (right)

METHODOLOGY

The Green Corridors project integrates an environmental network of vegetation connecting streams, hills, parks, and main roads in Medellin. The ecological system is composed of 18 road axes, 12 stream basins, and hills including Nutibara, El Volador, and La Asomadera.

The project methodology includes planting a variety of vegetation—trees, shrubs, palms—to lower ambient temperatures and reduce particulate pollution. From 2016 to 2019, a bioclimatic study conducted on the project measured temperature reductions and PM2.5 particle concentration reductions in targeted areas. As shown in Figure 2, The Metropolitan Area of the Aburrá Valley (MAAV) and associated Medellín urban zone, Departamento de Antioquía, Colombia. Background image: Landsat 8 OLI

Figure 2. The Metropolitan Area of the Aburrá Valley

BENEFITS OF NBS APPLICATIONS

The project provides both environmental and social benefits:

Environmental Impact: The Green Corridors successfully reduced temperatures by an average of 3.5°C in surface areas and 10.3°C in average temperatures from 31.6°C to 28.1°C in shaded zones. The PM2.5 levels saw a reduction of 1.55 µg/m³. Additionally, the newly planted vegetation in one corridor alone absorbs an estimated 160,787 kg of CO2 per year during its early growth phase, with a projection of 2,308,505 kg of CO2 absorbed over a 100-year lifespan.

Social Impact: The project provides employment opportunities to locals. Around 75 individuals from low-income backgrounds were trained to be full-time city gardeners and planting technicians. This has not only helped with job creation but also improved the community’s engagement with environmental initiatives.

Figure 3 shows Medellín's green corridors, while Figure 4 shows that the cable cars are directly connected to the subway, thus making it easy to reach even the most remote parts of the city.

Figure 3.Medellín's green corridors

Figure 4. Cable cars are directly connected to the subway

CHALLENGES

Despite its success, the Green Corridors project faces multiple challenges:

• Water Scarcity: Consistent irrigation for the vegetation is challenging due to limited water resources.
• Maintenance Costs: Regular upkeep requires substantial investment, adding pressure to the city's budget.
• Pollution & Environmental Stress: Urban pollution and stressors continue to threaten the longevity and health of the plants.
• Public Awareness and Engagement: Ensuring sustained public interest and understanding of the project’s long-term benefits remains a hurdle.
• Urban Expansion: As Medellin continues to grow, balancing the preservation of green spaces with new developments is difficult.

OUTCOMES

The project has had significant environmental and social impacts. The environmental cooling effect directly addresses the urban heat island problem, reducing temperature and particulate matter concentrations in high-traffic areas. The ecological corridors also improve biodiversity by providing habitat for various flora and fauna, enriching the urban ecosystem.

Socially, the initiative has created green public spaces that residents can enjoy, improving the city's livability and providing shade, which reduces heat stress for pedestrians. Community engagement through job creation has strengthened the city’s social fabric, with a particular focus on integrating low-income individuals into meaningful work related to environmental preservation.

A pedestrian walkway in Medellín is integrated with urban green space, featuring mature trees, benches, and patterned paving. The scene highlights the city's efforts to incorporate nature into its urban environment, offering a space for pedestrians and cyclists alongside the built infrastructure as shown in Figure 5.

Figure 5. A pedestrian walkway in Medellín

An elevated view of a public space in Medellín showcases its integration of greenery with pedestrian areas. Palm trees are planted in circular beds amidst a light-colored paved walkway, where people are seen walking and relaxing. The scene as shown in Figure 6, captures a vibrant urban environment designed for pedestrian use and social interaction.

Figure 6. Greenery with pedestrian areas

DISCUSSION

The success of Medellin's Green Corridors illustrates the powerful impact of nature-based solutions in urban environments. The project showcases how cities can leverage green infrastructure to address climate-related issues while enhancing social inclusion.

As street vendor Jesus Rodriguez mentions, “You can really feel the difference in heat when you’re in the shade and when you’re not.” Natalia Urrego, Medellin's infrastructure secretary, highlights the need for rethinking public spaces, stating, “Public space can't be grey and full of cement. You have to change the concept of public space. We must live together with nature.” However, small-scale challenges persist, such as plant theft for resale, as noted by gardener Vasquez. Regular evaluations and adjustments in policy will be necessary to ensure long-term success and community support for the project.

This project stands as an exemplary case of how environmental and social challenges in urban areas can be tackled through sustainable, nature-based solutions, offering valuable lessons for other rapidly urbanizing cities facing similar issues.

REFERENCES

1. Moloney, A. (2021). FEATURE-Colombia's Medellin plants 'green corridors' to beat rising heat. Reuters. https://www.google.com/search?q=https://www.reuters.com/article/colombia-medellin-green-corridors/ Retrieved October 27, 2024
2. Green corridors - Medellín, Colombia | Inspired by Nature-based Action and Solutions (INAS) - Showcase NbS. (n.d.). Inspired by Nature. https://www.google.com/search?q=https://www.inspiredbynature.org/green-corridors-medellin-colombia/
3. Reynolds, C. C., Escobedo, F. J., Clerici, N., & Zea-Camaño, J. (2017). Does “Greening” of Neotropical Cities Considerably Mitigate Carbon Dioxide Emissions? The Case of Medellin, Colombia. Sustainability, 9(5), 785. https://doi.org/10.3390/su9050785
4. "Alcaldía de Medellín - Green Corridors Initiative | NetworkNature." NetworkNature, https://www.google.com/url?sa=E&source=gmail&q=https://networknature.eu/green-corridors-medellin.

ABOUT AUTHORS

Tian Zelong. He is currently pursuing a Master's degree in Rail and Urban Transport (Transport) at the Technical University of Munich (TUM Asia) and holds a Bachelor's degree in Civil Engineering from Changsha University. With a developing background in supply chain management and transportation, he combines strong academic pursuits with practical experience, including logistics research and a patent for a wind tunnel testing device

Yang Qinyu. He is currently pursuing a Master's degree in Rail and Urban Transport at the Technical University of Munich (TUM) Asia in Singapore. He completed his undergraduate studies in Traffic Equipment and Control Engineering at Hunan University of Technology from 2018 to 2022.

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