17 September 2025
NTS Bulletin September 2025
Escalating Urban Heat: An Acute Challenge for the Sustainable Development Goals
Peili Pey
Urban areas are rapidly expanding; by 2050, 70% of the world’s population is expected to live in cities. This rapid, dense development has created a vital environmental challenge for living: the Urban Heat Island (UHI) effect. The UHI effect describes the phenomenon where urban areas are significantly warmer than their surrounding rural landscapes. This occurs because vegetation is replaced with materials like pavement and concrete, which absorb and retain heat. Additionally, waste heat from air conditioning units, vehicles, and industrial processes further elevates temperatures.
Urban heat is a grave sustainability and health crisis that is deeply intertwined with several of the United Nations’ Sustainable Development Goals (SDGs), particularly SDG 3 (Good Health and Well-being), SDG 11 (Sustainable Cities and Communities), and SDG 10 (Reduced Inequalities). This challenge is most accurate in the Global South, where low- and middle-income countries face the highest risk. By 2050, studies predict a catastrophic 700% global increase in the number of urban poor living in extreme heat conditions, with the largest increases expected in West Africa and Southeast Asia.
Cascading Impacts on Health, Energy, and Equity
SDG 3 (Good Health and Well-being) & SDG 11 (Sustainable Cities): The most direct impact of UHI is on human health (SDG 3). Urban heat amplifies the duration and intensity of heatwaves. Prolonged exposure to extreme heat compromises human health, increasing the risk of heat exhaustion, heat stroke, and heat-related mortality. This health crisis is directly linked to the functionality of our cities (SDG 11). As temperatures rise, the demand for artificial cooling surges. This increased consumption strains energy grids, raises utility costs for residents, and drives up greenhouse gas emissions, creating a dangerous feedback loop. This strain translates into massive economic losses due to reduced productivity. In Bangkok, an estimated baseline suggests heat-related labour production losses has reached 8.6 billion USD (projected to hit 16 billion by 2050).
SDG 10 (Reduced Inequalities): The burden of urban heat is not distributed equally, making it directly connected to SDG 10. Within the same city, temperatures can vary drastically, and research has shown that lower-income neighbourhoods are often hotter than wealthier neighbourhoods. These communities often have less tree canopy, denser pavement, while more reliant on public transportation, compounding their vulnerability. This vulnerability is acute for the labour force in the Global South. Projections for 2030 show that Southern Asia (5.3%) and Southeast Asia (2.2%) will lose a percentage of working hours to heat stress significantly higher than the world average (1.4%). This disproportionately affects urban poor and informal workers who lack the flexibility to adjust working hours and conditions.
Strategies for Resilient and Cool Cities
To accelerate progress for SDGs amidst this challenge, urban stakeholders must deploy integrated strategies that treat cooling as critical infrastructure:
Invest in Nature-based Solutions: This strategy focuses on green and blue infrastructure. Nature-based solutions are one of the most effective approaches to combatting UHI through evapotranspiration, including the planting of native trees, and expanding urban parks. Studies show that large urban parks can lower immediate surrounding temperatures by 2°C to 3°C. Blue infrastructure such as restoring urban streams also lowers ambient temperatures.
Redesign the Built Environment for Passive Cooling: Urban strategies must reduce heat absorbed by ‘grey’ infrastructure. Cities should move towards mandating high solar reflective (albedo) surfaces. This strategy also includes ‘smart design’, such as urban ventilation corridors, to disperse heat in dense ‘urban canyons’.
Implement Equitable Policies and Resilience Actions: Infrastructural changes must be supported by policy and social safety nets. Governments can encourage the adoption of solutions by creating financial incentives. For example, the Green Building Initiative in Quezon City, Philippines, offers up to 25% reduction in real property taxes for buildings that integrate sustainable practices. Importantly, investments in green infrastructure should be prioritised in historically underserved and hotter neighbourhoods. Equitable access to public cooling spaces (e.g. libraries or community centres)
should be ensured.
Addressing the UHI effect is fundamental to achieving SDGs 3, 10, and 11. By implementing smart, equitable, and nature-based urban design, stakeholders can build cities that are not only resilient to climate change but are healthier and more equitable for all inhabitants.
Escalating Urban Heat: An Acute Challenge for the Sustainable Development Goals
Peili Pey
Urban areas are rapidly expanding; by 2050, 70% of the world’s population is expected to live in cities. This rapid, dense development has created a vital environmental challenge for living: the Urban Heat Island (UHI) effect. The UHI effect describes the phenomenon where urban areas are significantly warmer than their surrounding rural landscapes. This occurs because vegetation is replaced with materials like pavement and concrete, which absorb and retain heat. Additionally, waste heat from air conditioning units, vehicles, and industrial processes further elevates temperatures.
Urban heat is a grave sustainability and health crisis that is deeply intertwined with several of the United Nations’ Sustainable Development Goals (SDGs), particularly SDG 3 (Good Health and Well-being), SDG 11 (Sustainable Cities and Communities), and SDG 10 (Reduced Inequalities). This challenge is most accurate in the Global South, where low- and middle-income countries face the highest risk. By 2050, studies predict a catastrophic 700% global increase in the number of urban poor living in extreme heat conditions, with the largest increases expected in West Africa and Southeast Asia.
Cascading Impacts on Health, Energy, and Equity
SDG 3 (Good Health and Well-being) & SDG 11 (Sustainable Cities): The most direct impact of UHI is on human health (SDG 3). Urban heat amplifies the duration and intensity of heatwaves. Prolonged exposure to extreme heat compromises human health, increasing the risk of heat exhaustion, heat stroke, and heat-related mortality. This health crisis is directly linked to the functionality of our cities (SDG 11). As temperatures rise, the demand for artificial cooling surges. This increased consumption strains energy grids, raises utility costs for residents, and drives up greenhouse gas emissions, creating a dangerous feedback loop. This strain translates into massive economic losses due to reduced productivity. In Bangkok, an estimated baseline suggests heat-related labour production losses has reached 8.6 billion USD (projected to hit 16 billion by 2050).
SDG 10 (Reduced Inequalities): The burden of urban heat is not distributed equally, making it directly connected to SDG 10. Within the same city, temperatures can vary drastically, and research has shown that lower-income neighbourhoods are often hotter than wealthier neighbourhoods. These communities often have less tree canopy, denser pavement, while more reliant on public transportation, compounding their vulnerability. This vulnerability is acute for the labour force in the Global South. Projections for 2030 show that Southern Asia (5.3%) and Southeast Asia (2.2%) will lose a percentage of working hours to heat stress significantly higher than the world average (1.4%). This disproportionately affects urban poor and informal workers who lack the flexibility to adjust working hours and conditions.
Strategies for Resilient and Cool Cities
To accelerate progress for SDGs amidst this challenge, urban stakeholders must deploy integrated strategies that treat cooling as critical infrastructure:
Invest in Nature-based Solutions: This strategy focuses on green and blue infrastructure. Nature-based solutions are one of the most effective approaches to combatting UHI through evapotranspiration, including the planting of native trees, and expanding urban parks. Studies show that large urban parks can lower immediate surrounding temperatures by 2°C to 3°C. Blue infrastructure such as restoring urban streams also lowers ambient temperatures.
Redesign the Built Environment for Passive Cooling: Urban strategies must reduce heat absorbed by ‘grey’ infrastructure. Cities should move towards mandating high solar reflective (albedo) surfaces. This strategy also includes ‘smart design’, such as urban ventilation corridors, to disperse heat in dense ‘urban canyons’.
Implement Equitable Policies and Resilience Actions: Infrastructural changes must be supported by policy and social safety nets. Governments can encourage the adoption of solutions by creating financial incentives. For example, the Green Building Initiative in Quezon City, Philippines, offers up to 25% reduction in real property taxes for buildings that integrate sustainable practices. Importantly, investments in green infrastructure should be prioritised in historically underserved and hotter neighbourhoods. Equitable access to public cooling spaces (e.g. libraries or community centres)
should be ensured.
Addressing the UHI effect is fundamental to achieving SDGs 3, 10, and 11. By implementing smart, equitable, and nature-based urban design, stakeholders can build cities that are not only resilient to climate change but are healthier and more equitable for all inhabitants.
