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Earth Day 2023

Earth Day is upon us once again. It is likely that your attractive friends from college will post montages of waterfall pictures from their travels around the world, accompanied by captions that straddle the thin line between sentimental and out-of-touch. Maybe your neighbor will organize a group hike, camping trip, or biking excursion. Almost certainly, the brands whose email subscriptions you neglected to cancel will inundate your inbox with Earth Day-inspired promotions and a detailed rundown of their environmental, social, and governance (ESG) commitments.

For the most part, this is all well and good. Any celebration of our planet’s natural beauty or extra attention focused on our dire climate situation cannot be considered a bad thing. However, although it is important to appreciate our planet’s splendor, a greater sense of urgency and pragmatism are needed to address our current environmental crisis. As Jeff Goodell writes, “We don’t need pretty pictures – we need action.” We must recognize that we are not passive inhabitants of this planet and the Earth is not, in itself, fragile; rather it is humanity’s peaceful coexistence with the Earth that we must fight to protect.

The recent Synthesis Report published by the Intergovernmental Panel on Climate Change (IPCC) offers a clear warning: “There is a rapidly closing window of opportunity to secure a livable and sustainable future for all…the choices and actions implemented in this decade will have impacts now and for thousands of years.” This fact, presented so starkly, should not simply set off alarm bells; it must inspire immediate action. But how are we to wage battle against an intractable, unrelenting, invisible enemy of our own making? One promising tactic is to concentrate force. More specifically, concentrate force in cities.

The IPCC report is explicit: “Urban systems are critical for achieving deep emissions reductions and advancing climate resilient development.” Sustainable urban development will help mitigate present and future climate emissions, while also furthering global adaptation efforts and providing for the 68% of the world’s population who will be living in cities by 2050. There is no denying that our climate situation is grim, but there are viable solutions amid an ever-narrowing window for action. To effectively invest in our planet, we must immediately invest in our cities.

Cities are unquestionably significant contributors to the climate crisis. Despite comparatively low per capita emissions, urban areas account for almost three quarters of the world’s total CO2 emissions as a consequence of “industrial and motorized transport systems that use huge quantities of fossil fuels and rely on far-flung infrastructure constructed with carbon-intensive materials.” Furthermore, as cities across Africa and Asia grow to accommodate an additional 2.25 billion urban residents by 2050, urban emissions and energy demand are only expected to increase.

Nonetheless, it is precisely because cities are the biggest emissions culprits that targeting carbon-intensive energy, transit, and infrastructure systems in urban centers is a crucial mitigation tactic. Increasing urban density through land use policy can help lower transportation emissions and improve energy efficiency. In fact, there is a strong negative correlation between density and per capita emissions in cities throughout East Asia and the Pacific, the Middle East and North Africa, and North America and Europe, as well as a weak negative correlation in Latin America and the Caribbean and Sub-Saharan African (See Figure 1).¹

Charts showing Urban Density and Per Capita Carbon Emissions
Author’s calculations using data from the Global Human Settlement Layer.

Furthermore, many climate change mitigation strategies – such as establishing requirements for building insulation, improving waste management systems, or increasing accessibility of low-carbon transit – are highly viable at the municipal level. For example, since 2012, Copenhagen has engaged in the expansion of bike lanes throughout the city as part of efforts to reach carbon neutrality by 2025. Now, over 62% of residents commute to work or school via bike, with bikes outnumbering cars five to one. Proactively integrating similar climate-conscious urban systems into the design and planning of settlements in burgeoning cities can help prevent lock-in of high emissions infrastructure. Such efforts will be particularly important in developing countries as urban populations continue to grow and cities swell to accommodate the influx.

As home to the majority of our population, cities must also be prepared to protect their residents from extreme weather events and withstand the harmful effects of climate change. As Goodall notes, “the earth, truth be told, is not a dependable source of hugs and forgiveness for us humans. Nor does nature itself hold us in high esteem just because we’ve figured out a way to send photos of puppies across the planet instantaneously.” Mother Nature is not vengeful; she adapts. The challenge for us humans is to adapt in turn as our planet transforms. 

Already, the impacts of climate change are being poignantly felt in urban areas. For one, rising temperatures threaten to turn cities into urban heat islands. Extensive pavement and other infrastructure surfaces absorb and re-emit heat, turning cities into urban ovens during heatwaves. Recent work by Tuholske et al. (2020) finds that between 1982-2016, global exposure to extreme heat in urban areas “increased nearly 200%, affecting 1.7 billion people,” (see Figure 2).

Chart showing Urban Extreme Heat Exposure in 2016
Author’s calculations using data from Tuholske et al. (2020).

Furthermore, urban areas have become increasingly vulnerable to flooding, due to both increased exposure to intense, unpredictable weather and urban expansion into flood zones (see Figure 3). For example, a recent study finds that in Mumbai, rural residents moving to the city in search of economic opportunity are often relegated to “high-risk flood zones near riverbeds, [where] informal settlements grow without planning or public infrastructure.” The authors observe similar patterns in Ho Chi Minh City and Bangkok.

Graph showing Potential Urban Flood Exposure in 2015
Author’s calculations using data from the Global Human Settlement Layer.

Hasty, unsupervised, and unsound construction in urban expansion zones increases the likelihood of damage to infrastructure and dwelling units during floods and severe storms. As of 2018, over one billion people worldwide were living in informal urban settlements. Climate migration – including refugees, internally-displaced peoples, and economic migrants whose livelihoods have been devastated by climatic changes – will undoubtedly contribute to the growth of unplanned settlements. Urban slum proliferation, poor service provision, weak infrastructure, low household adaptive capacity, and high risk of exposure to extreme weather events not only heighten climate vulnerability, but, most importantly, have devastating ramifications for human well-being.

However, policies to promote orderly, efficient urban expansion – such as pre-emptively installing arterial roads and public facilities in expansion zones – can help minimize urban sprawl and lay a strong foundation for future growth. Investing in climate-conscious infrastructure plans and nature-based solutions can also support urban resilience. For example, a growing number of cities are turning to urban parks and green spaces to insulate against the impacts of climate change.

Urban parks provide a multitude of benefits for the cities they serve: they absorb excess water during periods of intense rainfall; mitigate the ‘heat island’ effect; reduce air pollution; protect biodiversity; and promote social cohesion. However, many of the countries in regions which stand to be the most severely impacted by climate change have a low average urban green space per capita. In fact, no low-income countries and only three lower-middle-income countries – Sri Lanka, Bangladesh, and Zimbabwe – rank in the top 25 for average urban green space per capita (see Figure 4). Urban green spaces remain an underutilized climate adaptation strategy.

Graph showing the Average Urban Green Space Per Capita in 2014
Author’s calculations using data from the Global Human Settlement Layer.

Finally, as the IPCC suggests, “mitigation and adaptation actions have more synergies than trade-offs with [the United Nations’] Sustainable Development Goals.” Policies designed to promote mitigation and adaptation efforts in urban areas can – and should – simultaneously support economic growth. As urban economist Ed Glaeser argues, there is “a near-perfect correlation between urbanization and prosperity across nations.” Establishing resilient cities helps reduce risk and improves stability, but it also improves the health and well-being of citizens, allowing them to engage as creative, productive members of society.

After all, the flourishing of human civilization is what we must fight to preserve from the harmful impacts of climate change. As Glaeser argues, cities are humanity’s greatest invention, and though they are partly culpable for climate change, they are more than capable of leading the charge against it.  This Earth Day, we must move beyond sentimental appreciation for our planet and remember our own agency in building a sustainable, prosperous future for all. 

¹ Among predominately developing regions, the only exception to this phenomenon is South Asia. This is driven in part two outlier cities in India – Visakhapatnam (omitted from Figure 1) and Berhampur – which are industrial and transport centers. However, more research is needed to investigate this further. It is also important to note that this analysis only include cities that have a population over 1 million. 

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November 16-18, 2023 | Kigali, Rwanda


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