Issue Profile

Conclusion

The global center of gravity is increasingly shifting to cities. Urban areas hold just over half of the world’s population,¹ generate roughly 80 percent of global GDP, ² and drive 70 percent of global energy-related carbon dioxide emissions.³ 3.9 billion people currently live in cities, a number expected to climb to 6.4 billion — two-thirds of the world’s population — by 2050.⁴

The stakes of cities’ environmental and sustainability policies over the following decades are exceptionally high. Many of the Global South cities projected to grow the most have the fewest per capita financial resources.⁵ City leaders in these areas often face a difficult balancing act between addressing the urgent and growing need for essential services, and making longer-term decisions and investments that will shape the urban environment — and its residents — for years to come.⁶ In more developed cities, officials must grapple with previous land-use and infrastructure decisions that have led to unsustainable levels of resource consumption and set up costly paths for continued development.⁷⁸⁹ Around the world, shared challenges such as air pollution and climate change place millions at risk.

Cities also hold unique opportunities to foster equitable and sustainable growth. Denser, more connected, and more coordinated cities could save $17 trillion USD by 2050.¹⁰ Compact urban areas could increase residents’ access to jobs, services and amenities, while reducing infrastructure costs.¹¹ City policies and practices can help mitigate climate change and build resilience to its impacts.¹²¹³

As cities take on increasing leadership in charting a trajectory that navigates these challenges, the goals of fostering inclusive, equitable development and successful environmental management are deeply intertwined. Environmental burdens and risks — such as air pollution, heat waves, extreme weather events, and the risk of floods and droughts — can sharpen inequality,¹⁴¹⁵¹⁶ while access to environmental benefits, such as green space and public transit, can help mitigate it. Building public transit to connect underserved communities to the city center helped Medellin, Colombia transform from the world’s murder capital to into a safer and more inclusive city.¹⁷¹⁸ Programs fostering social cohesion can lessen the impacts of urban heat waves and build resilience to extreme weather events and natural disasters. ¹⁹²⁰²¹

Data will be imperative to enabling cities to address these integrated challenges. At the moment, frameworks that compare cities’ progress and challenges — and assess how this performance varies across different neighborhoods — remain scarce. The UESI provides a resource that tracks neighborhood-level access to environmental goods and exposure to environmental harms to help city managers and urban residents understand how the environmental quality of life varies across different locations and socioeconomic demographics. Building on our experience, we have leveraged the potential of large-scale and unconventional datasets — from satellite data to OpenStreetMap — to create a detailed, timely, and comparable framework for cities to track sustainable and inclusive environmental performance. Over time, the UESI aims to provide a flexible and adaptable framework and data source that new cities can adapt for their own analysis and management purposes, while increasing and updating its base indicators using the latest data sources and advances in data science.

The results of the latest version of the UESI show that cities are still not meeting the charge of sustainable and inclusive environmental policies. Although there are some cities that perform well on the UESI’s environmental indicators, almost half of them are burdening poorer populations with the consequences of uneven air pollution distribution, access to tree cover, public transit, and exposure to urban heat. We see that income still plays a strong role in determining environmental performance in many cities, however we also see cities breaking from this pattern, highlighting that other factors besides income are also relevant to achieve positive environmental performance . Higher levels of income, however, do not determine equitable outcomes, as the UESI results show wealthy and poor cities alike are placing the greatest environmental inequalities on poorer populations. For instance, urban heat island intensity places a greater burden on poorer populations in Bologna (ITA), Lisbon (PRT), Los Angeles (USA), and Mexico City (MEX). Lima (PER)‘s high levels of income inequality are compounded by inequitable distributions of urban heat island, air pollution, urban tree cover, and distance to public transit, which disproportionately burden lower income earners.

Data gaps still remain: vital socioeconomic data still proves especially difficult to collect and standardize across different urban contexts, while tools like OpenStreetMap are prone to gaps in volunteers’ data collection. Data alone, however, is not a panacea — cities’ ability to investigate and respond to data signals depends on technical knowledge, financial resources, and political will. The continued growth of mobile phones and information communication technology and the innovation in new modes of data collection have the potential to help ground and inform cities’ growing role in fostering sustainable development. We hope this tool continues to serve decision makers, researchers, and citizens alike, sparking further discussions about the role of data in support of urban sustainability to create a more robust dataset of urban triumphs and challenges, and to mobilize support for efforts to chart a safe, inclusive future.