By Ana V. Diez Roux, MD, PhD, MPH

Two examples this month, one more local and one more global, but both equally powerful, have brought home the dramatic effects our planet, our lives, and our health are experiencing as a result of global climate change. They also highlight how social justice, environmental impacts, and our economic system are inextricably linked.

Just last week, a study led by Vivek Shandas of Portland State University, and extensively covered in the New York Times, highlighted how increases in temperature are affecting cities throughout the United States and more specifically — how temperature varies dramatically across neighborhoods within cities. The study showed, for example, how on a hot, summer day temperatures can differ by as much as 20 degrees Fahrenheit across neighborhoods within a city, with poor and minority neighborhoods being the most affected by heat. As the study authors noted, it’s not only that cities are often warmer than the surrounding areas (the well-established urban heat-island effect), but also that within cities some neighborhoods experience significantly more heat than others. It’s no surprise that poorer neighborhoods are more affected: they tend to have more paved surfaces and asphalt to absorb and reflect heat and less parks and green cover, both known to have a cooling effect. 

The health impacts of heat are well-known. It is also well-established that the health impacts of heat are greater in individuals with pre-existing health problems, in children, and older individuals. Adverse health conditions in residents of poor neighborhoods thus magnify the adverse impact of heat. In addition, residents of poorer neighborhoods have fewer resources to buffer or escape the impact of heat. Their homes are less insulated from heat and they are less likely to have air conditioning. At the same time, and in a perverse twist, wealthier neighborhoods benefit from larger homes with air conditioning, and from consumption patterns (such as more cars and more energy consumption overall) that reinforce the global warming that affects disadvantaged groups (not just in their own city but all over the world) the most.

And then on the global front, we have the devastating fires in the Amazon. Aside from its very real impact on the world’s climate, the symbolism of the images is hard to understate: a burning jungle, fleeing animals, an aftermath of devastation and desolation. The causes of the fires are likely complex but certainly economic drivers and political inaction, as well as subtle and not-so-subtle signs by some world leaders that perceived economic imperatives trump environmental concerns, are major contributors. The health impacts of fires like these are extraordinary and operate through both direct and short-term effects (e.g. air pollution impacts, as starkly illustrated by the smoke over Sao Paulo) and through more long-term effects on green-house gasses resulting from the loss of biomass.   

Just as the distribution of heat in the city mirrors and reinforces inequities in health and environmental conditions by class, race, and ethnicity, large scale global environmental catastrophes like the Amazon fires (or global warming itself) reinforce global inequities. They do not affect all countries or all cities equally: poorer countries, poorer cities, and poorer people within those cities will bear the brunt of higher temperatures, flooding, famine, and drought. This despite the fact that on a per capita basis, poorer countries and poorer people within them consume significantly less energy than wealthier countries and people, and therefore from a moral perspective bear less responsibility for the state we are in and have less latitude to change their consumption patterns.  

The elephant in the room is of course a social and economic system that has on one hand supported and encouraged consumption patterns linked to environmental degradation, and on the other hand generated and sustained pronounced social inequalities. Population health and environmental sustainability cannot be understood without reference to these underlying systems. So as public health professionals, or simply as citizens of the world, we cannot be on the sidelines. We must study, make visible, disseminate and act, personally and as a community. The heat in the city and the fires in the jungle are different aspects of the same crisis: a crisis that should motivate us to challenge and think differently about how we organize our society to protect our health, promote social justice, and ensure the survival of our planet and future generations.