Overheating megacities are a climate problem and solution – a Latin America case study 

It can seem like climate change affects all communities equally. From flash floods and wildfires to record-breaking heat waves, its impacts are spreading – from the parched well-to-do neighbourhoods of California’s suburbs to Pakistan's waterlogged cities spanning Peshawar to Hyderabad.

On closer inspection, however, the impacts of climate shocks and stresses are uneven. “I wish I could tell you why areas where people may not have much continue to get hit and lose everything,” Kentucky Governor Andy Beshear said last month, after the worst floods in a quarter century engulfed poverty-stricken Appalachia.

No state or city is exempt from the global climate emergency. But certain cities and neighbourhoods are more at risk than others. Latin America, the second most urbanized region in the world is a case in point – where the ravages of rogue weather are most stark in its burgeoning megacities. Like pandemics, crime or inflation, climate upheaval hits the most vulnerable people hardest.

In Latin America, rapid urbanization is trampling green spaces and sucking water sources dry. Most of its cities are constructed of steel and concrete and with ever-burgeoning traffic, they are colossal heat traps.

As cities sprawl, they also leave a trail of depleted groundwater, “dead” rivers, denuded watersheds, paved floodplains and desiccated landscapes. Soaring demand for water means one in four cities worldwide are now prey to shortages. By the mid-century, many new megacities will suffer from chronic water scarcity.

With substantial increases in mean annual temperatures and extreme heat locked in, Latin American cities offer a glimpse of the future. Rio de Janeiro’s coastal favelas are doubly menaced by rising seas and soaring temperatures, while Mexico City is sinking as the groundwater dries beneath.

The number of extremely hot days in Latin America is set to multiply by five to 10 times by 2050. Every additional one degree Celsius increase is projected to increase mortality risk by nearly 6%, researchers project, with adverse effects anticipated in Argentina, Brazil and Mexico.

Heat also generates lasting social and economic damage. A World Bank study of middle-class workers in Ecuador found that individuals subjected to rainfall shocks and extreme heat reported lower formal sector earnings than their peers 20 to 60 years later.

Yet cities are also fighting back against global warming: more than 11,000 cities worldwide have already signed a covenant to reach net-zero carbon emissions by 2050. To get there, they must radically strengthen the carbon-saving circular economy.

First, they should decarbonize their energy grid and transition to renewables such as solar, wind, biomass and green hydrogen. Wherever possible, they should encourage car-less transportation, public transport and micro-mobility, including bike lanes, scooters and pedestrian walkways.

City planning and architecture need a green upgrade through the redesign of offices and homes with smarter energy-efficient materials and more sustainable management practices. Many new cities have an opportunity to literally design-in climate resilience: developing nations will account for half of the new building stock by 2050.

Next, cities must ditch suburbia and embrace urban density instead. Compact cities like Barcelona, Copenhagen and Singapore are getting to grips with heat by building more compact neighbourhoods, reducing dependence on cars and seizing the green virtues of proximity.

Finally, cities must go nature-positive by investing in parks, pathways and waterways – the green and blue spaces vital to urban living. City managers can reduce heat and risks of floodplains by rewilding, sowing green roofs and raising nature-friendly “biophilic” buildings.

Mexico City’s Isidro Fabela is a stand-out model. With parsimonious use of natural gas, self-help home building, reliance on public transportation and recycled materials, the modest barrio economizes on energy. It emits half the greenhouse gas per household of the average Mexico City dwelling.

Encouragingly, other Latin American cities are following suit and signing on to climate mitigation pacts, including mayors from Buenos Aires, Curitiba, Guadalajara, Lima, Medellín, Mexico City, Quito, Rio de Janeiro, Salvador and São Paulo.

Some are slashing emissions from transportation, offices and residential buildings, energy production and waste management while simultaneously investing in adaptation strategies. For example, Medellin is harnessing the cooling effects of trees by planting them in parks and along city streets.

Another coalition of Latin American mayors recently agreed to launch a new model of urban development that conciliates biodiversity as a backstop against climate change. The Biodivercities initiative is supported by the Andean development bank (CAF) and integrates biodiversity, ecosystem services and carbon reduction into municipal planning.

Although Latin American cities suffer environmental liabilities, they also benefit from unique natural assets. While European and North American cities are racing to restore depleted green enclaves, cities of Latin America need only protect their extraordinary endowment of forests, rivers and fauna.

Yet biodiversity in many Latin American cities cannot be taken for granted – their restless expansion is encroaching on protected areas. This encroachment is double jeopardy in a deepening climate crisis. Cities are not just losing precious green space but hurling more emissions into the atmosphere. Brazil, for instance, trails only Nigeria and the United States in carbon emissions from habitat loss due to urban growth.

Latin American cities need to upgrade their urban planning and crack down on resource predators to capitalize on their subsidy from nature. As ever larger swaths of the planet bake, burn and drown, city leaders could take their cues from places like Mexico City’s Isidro Fabela or Brazil’s Curitiba, one of the greenest cities in the world.

These examples may appear trifling in an age of runaway climate change. But they stand out as inspired case studies of how even those with little can still tread lighter on the planet while building a greener future.