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Something as ordinary and pleasant as walking on the street on a summer day could become a risky activity in many cities around the world. The reason? Everything suggests that if we don’t act quickly, our cities will become too hot to allow it. Consequently, this will negatively impact the productivity of our municipalities, the quality of life of those who reside in them, and the health of the entire planet.
In this article, which is part of a series on the future of cities in Latin America and the Caribbean (LAC), we share some of the climate challenges facing urban areas and their effects on the population. Keep reading to learn all the details!
Extreme heat
One of the most obvious effects of climate change, which already affects many cities in LAC, is the urban heat island (UHI). What is this phenomenon about?
The UHI is a phenomenon that occurs in urban areas experiencing higher temperatures than surrounding areas. The density of buildings, the large expanses of impervious surfaces, and the limited tree canopies and vegetation coverage in cities create UHIs.
The UHI is one of the factors causing urban spaces heating up at twice the rate of the global average. In LAC’s eight largest cities, the UHI effect will raise urban temperatures by 3°C to 8°C. By the mid-21st century, the frequency of extremely hot days (defined as days above the 95th percentile of the distribution of daily mean temperature between 1961 and 1990) will increase by five to ten times in South America’s largest cities.
Left: Satelital image obtained with URSA, an IDB software, detecting UHIs | Right: Image of Sao Paulo during summer
If that weren’t enough, urban residents’ behaviors and consumption patterns can further increase local temperatures. For example, to cope with high temperatures, residents increase their use of cars and air conditioning (AC), which expels more hot air as exhaust and also consumes more energy, frequently via fossil fuels. All this, in turn, worsens air pollution and contributes to climate change. If left unchecked, the increased use of cars and AC will cost the average city nearly 6% of its economic output.
Heat effects: health risks and vulnerable populations
Rising temperatures can have a negative effect on our health. It is proven that that the hottest cities are correlated with worse public health indicators. Hotter cities create health hazards and economic disruptions. For example, extreme heat and prolonged heat waves increase the risk of illnesses and death through heat stress, the propagation of pathogens, and the spread of disease vectors such as dengue and other parasites.
Furthermore, higher temperatures facilitate the propagation of pathogens transmitted by food, water, insects, or other animals, which is a concern for urban markets. Hot climates extend the life cycle of mosquitoes, ticks, and rodents that carry diseases. Cities’ higher population density favors the rapid spread of diseases, particularly in neighborhoods lacking adequate sanitation and sewerage services.
Heat doesn’t affect everyone equally. Low income households suffer it more because they tend to be located in less insulated buildings and hotter areas of the city, at the same time as they cannot afford AC units to help them cope with heatwaves. In LAC, less than 10% of all households have AC. Data confirms the importance of AC for managing heat in urban areas. For example, in the United States, the diffusion of residential AC resulted in a 75% decrease in the mortality impact of days with an average temperature above 26.6°C.
Water security
The future of our cities will not only be warmer but also drier. Higher air temperatures promote the creation of drought conditions and often increase them. If we add to this a growing population, and a poorly maintained and insufficient water supply, we get a scenario where water access security may not be guaranteed for all city residents, especially those in informal settlements. Some cities in the region, such as Mexico City in Mexico, and La Paz in Bolivia, already suffer from freshwater stress caused by climate change.
Additionally, urban growth and higher temperatures are expected to further increase water demand both directly (for human consumption) and through higher energy use. since hydropower and electrical power generation use large amounts of water. As a consequence, water scarcity can lead to electric shutdowns and power outages for firms undermining economic activities in cities.
Water access security may not be guaranteed for all city residents, especially those in informal settlements
But the effects of heat and water security don’t end there. A study using monthly labor force surveys from 78 cities in Latin America, demonstrates the direct correlation between water availability and employment. Specifically, it shows that large sustained dry events decrease the probability of being employed, hourly wages, hours worked, and labor incomes. It also makes it clear that informal workers are the most impacted.
Fires
The combination of rising temperatures, prolonged droughts, and rapid urban growthv fosters a greater impact of wildfires in urban areas near wildlands.
From 2015 to 2018, wildfires affected a record-breaking 152 countries around the globe. These phenomena are devastating. Wildfires cause deforestation, increase susceptibility to landslides, and disrupt air transportation by reducing visibility. In addition to direct injuries and deaths, wildfires can cause eye and respiratory illnesses. For example, in 2017, Chile suffered the most intense landscape fire ever registered on Earth at that date. It is estimated that 74% of the Chilean population (nearly 13 million people that year) was exposed to an unusual increase in particulate matter levels due to wildfire smoke. A long-term study in Chile found a dose-response relationship was also observed for pneumonia, showing that it affects younger children particularly when there is an increase in the number of wildfires.
Chile suffered the most intense landscape fire ever registered on Earth at that date
How to prevent and mitigate the effects of climate change in our cities?
If appropriate policies are not adopted in time, our cities will become warmer, drier, unhealthier, and more vulnerable to fires. Climate change poses risks to cities that threaten people’s lives and businesses.
In the next article in this series, we will address what are the most effective tools for managing climate change. Some of these include green/grey infraestructure, urban regulations, promoting behavior change among residents, and improving the local governance framework.
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