Cooling Down Our Cities using "Green Corridors" – Innovation in Climate Change Adaptation Jem Golden

I have posted a number of blogs recently on equal access to urban green spaces (UGS) and spatial justice including a case study in Helsinki that identified the green areas that are the most important for equitable accessibility to recreation for all Helsinki citizens incorporating multi-modal means of transport to the main green areas in the city. 

Also, for Seoul, I analysed urban park provision by the size, type, and spatial accessibility of parks including for citizens of low socioeconomic status using a wide range of park provision metrics. 

Analysis for Kuala Lumper highlighted the ‘alteration’ of UGS by commercial developers denuding multiple categories of greening areas including supposedly ‘reserved’ forests, this is not only a spatial justice infringement that accelerate climate change at an alarming rate. 

Multiple initiatives in the Global South and Global North have highlighted the importance of boosting green urban areas and connecting fragments of green space with “green or ecological corridors”. Whatever the starting point, the objective of a green corridor is always to link important natural areas in a city by means of a strip or corridor characterised by rich vegetation. 

If adequately designed, green corridors can improve urban ventilation, allowing for cooler air from outside to penetrate into the more densely built areas, and so reducing the urban heat island effect. Urban green areas can also have positive effects for human health and climate change adaptation. The capacity of vegetation to retain water is an important flood prevention feature that can reduce peak discharges.

Green areas are often threatened by expanding city structures, which have fragmented natural areas, creating small patches of green spaces in amongst buildings and roads. For example, patches of urban woodlands are generally separated from each other, which affects the ability of many woodland species to disperse, or move among different locations with similar habitats.

The wide array of available techniques allows application in areas with very different characteristics and even where space is limited. Techniques include, for example, green roofs and walls which use vegetation on the roofs and facades of buildings to provide cooling in summer and thermal insulation in winter. 

As a result of 50 years of rapid urban development, Medellín, Colombia’s second largest city, was experiencing a severe urban heat island effect. To address this phenomenon, the city implemented a ‘greener Medellín for you’ programme, significantly shifting its urban design paradigm.

Since 2016, Medellín, has created 30 ‘Corredores Verdes,’ an interconnected network of greenery across the city. This ambitious initiative adds to and further connects existing green spaces, improves urban biodiversity, reduces the city’s urban heat island effect, soaks up air pollutants, and sequesters a significant amount of carbon dioxide. 

As part of the million initiative, citizens from disadvantaged backgrounds were trained by Medellín’s Joaquin Antonio Uribe Botanical Garden to become city gardeners and planting technicians. They have helped to plant over 9,000 trees and palms in the 30 corridors that cover 65 hectares.

Diagram above gives figures calculated from the C40 Heat Resilient Cities tool for Medellín Green Corridors project. It shows the key benefits from the current Green Corridors area (highlighted in blue), as well as potentially further extending this to cover 12% of the city (green highlighted), which is the recommended average green space per inhabitant for Medellín.

These Green Corridors provide Medellín with a host of ecosystem benefits: they help to reduce average city temperatures by 2°C, enable carbon uptake via plant growth, capture particulate matter (PM2.5) to improve air quality, and increase urban biodiversity thanks to creation of more wildlife-friendly habitats.

 Photo: A man walks near the vertical garden of a building at the Alpujarra sector in downtown Medellin, Colombia. (Photo- Joaquin Sarmiento/AFP)

However, mitigating the rising heat also in Medellín’s most vulnerable poor neighbourhoods require city leaders and planners to focus on these impoverished communities most exposed to climate change and to the lack of green infrastructure. While more cool, inviting green public spaces now dot many of Medellin's poor neighbourhoods and its centre, surrounding hillside slums of brick-and-tin homes lack even the most basic vegetation and public parks.

 Photo: A view of hillside slums without significant green plantings in Medellin, Colombia, July 17, 2021. Copyright: Thomson Reuters Foundation/Anastasia Moloney

Therefore, an important consideration for ‘green corridor’ implementation should be to evaluate who is included or excluded from these ecological change processes, and therefore which social group adaptation may benefit the most. For instance, tree planting may be a more likely adaptation strategy for wealthier neighbourhoods, but difficult to implement in densely packed informal settlements where there is little open space for tree plantings, leaving such communities even more vulnerable and therefore other more creative and radical ‘nature-based’ options have to be considered.

Sources for article on Medellín and urban cooling project

Colombia's Medellin plants 'green corridors' to beat rising heat

https://news.trust.org/item/20210728130018-qufqy/ 

Urban green space in Medellín: Who has the least?

https://www.peak-urban.org/blog/urban-green-space-medellin-who-has-least 

Colombia: Green Corridors Help Reduce Heat Risk in Medellín

https://www.preventionweb.net/news/colombia-green-corridors-help-reduce-heat-risk-medellin 

Cities100: Medellín’s interconnected green corridors

https://ramboll.com/-/media/files/rm/c40---heat-resilience/c40-case-studie-medellin.pdf?la=en

Ciudades Cada Vez Mas Verdes

https://www.abc.com.py/estilo-de-vida/2021/08/05/ciudades-cada-vez-mas-verdes/