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Climate change is no longer an abstract concept but a current challenge in our cities. As we analyzed in the previous article of this series, the rise in average temperatures and intense heatwaves, droughts, wildfires, and floods are some of the extreme weather phenomena that increasingly affect densely populated urban centers.
What can cities in Latin America and the Caribbean (LAC) do to protect their inhabitants and economy from the effects of climate change? Some of the most effective tools include the construction of gray and green infrastructure, urban regulations (including land use regulations and building codes) and improving the local governance framework.
In this article, we will analyze the important role played by green and gray infrastructure as complementary and essential tools in protecting cities from adverse climate phenomena. Keep reading to learn more details!
Green infrastructure: nature in the city
Urban green infrastructure (UGI), also known as nature-based solutions (NBS), is an innovative concept based on the revaluation of vegetation in cities. It materializes in the use of natural and semi-natural spaces within urban areas, such as parks, gardens, green corridors, and conservation areas, to improve climatic conditions and the resilience of cities.
An example of NBS is planting trees and increasing the tree canopy area to reduce extreme heat in cities (including heat islands), with co-benefits for people as trees reduce pollution and its health consequences health. In Medellin, Colombia, the Green Corridors program led to a 2°C drop in the city’s average temperature. In Rio de Janeiro’s Favela Green Roof pilot program, homes with green roofs were up to 20°C cooler indoors during peak heat than those with traditional roofs.
Cities can also explore green infrastructure options to manage excessive rainfall and sea level rise. For example, Buenos Aires, Argentina, created a 36-acre national park to restore the floodplain. Similarly, Curitiba, Brazil, relies on permeable pavements, urban parks, and green areas to manage rainfall. Coastal cities can use native vegetation, such as mangroves and wetlands, to store water, stabilize shorelines and reduce storm surges. For instance, mangroves can reduce the height of waves by up to 66% and storm surges by up to 55 centimeters, which could help protect more than 18 million people and $82 billion in assets. The benefits that green infrastructure delivers in terms of prevented damage can be substantial. As one estimate, existing wetlands prevented $625 million in property damage during Hurricane Sandy in the United States.
Gray infrastructure: technology serving the environment
The term gray infrastructure refers to the construction of engineering solutions, such as drainage systems and water and energy supply networks, to manage the environment. Although these constructions have traditionally been associated with negative environmental impacts, gray infrastructure also plays an important role in mitigating and adapting to climate change when designed and managed sustainably.
This type of infrastructure can help cities adapt to flooding, through seawalls and breakwaters, dikes, floodgates, levees, and even temporary sandbag barriers and to other challenges such as extreme heat. For example, in Barbados, the government has turned to coastal engineering to protect the southwest and west coasts where erosion is common. Similarly, Guyana uses seawalls to address coastal flooding and elevated pump stations in areas where flooding could occur.
LAC cities could also implement district cooling system (DCS) to cool its high-density urban areas. DCS recycles the waste heat from chillers and uses it for space heating or hot water production, and it uses 20 to 35 percent less electricity than traditional AC systems. Paris has implemented DCS as part of its climate change plans.
While grey infrastructure can be effective, it can also be expensive; the capital costs for sea dikes in LAC under the medium sea-level scenario (from 2010 to 2040) is US$7.1 billion per year. The global maintenance and investment costs of protecting coastal areas with dikes are estimated at $12 billion to $71 billion annually by 2100.
Complementarity and synergies
Sustainable urban planning can leverage both green and gray infrastructure to create more livable and healthier urban environments. Although they have different approaches, they are complementary, and when implemented coordinately, their benefits are maximized. For example, an urban plan that combines urban parks, energy-efficient housing, with a multimodal public transportation network promotes more equitable and resilient urban development. In summary, effectively addressing the challenges of climate change in cities requires exploring green infrastructure options that work in harmony with ecological systems.
In the next article of this series, we will address the importance of complementing green and gray infrastructure actions with improvements in urban regulations and the local governance framework to enable sustainable and sustained adaptation.
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