Changing Places
Changing Places
Changing Places

Changing Places

Kashmere Gardens has seen better days. In this neighborhood of northeast Houston, modest ranch homes are framed by murky drainage ditches and rusting chain-link fences. About 15 percent of its residents are unemployed, and most of those who aren’t make less than $23,000 per year.

The neighborhood is tucked between an industrial park, a major train depot, and Hunting Bayou, a muddy trickle that stretches for miles through a grass-filled depression. Although technically a creek, the bayou is barely lower than the surrounding land. It was one of the first places to flood when Hurricane Harvey dumped nearly 50 inches of rain on the region in August 2017, sending water and debris chest-high into the neighborhood’s homes.

Spring | 2018
by David Levin

The deluge exposed residents to dangerous skin infections from bacteria-laden floodwaters and to carcinogens from overwhelmed chemical plants and Superfund sites nearby.  It swamped utility lines, depriving residents of fresh water, and caused raw sewage to overflow from sewers and septic tanks—in some places, tainting floodwaters with 135 times the safe levels of E. coli bacteria. In short, it created a barrage of public health risks that plagued the neighborhood—and the rest of the Houston metro area—in the days following the storm.

Months after the disaster, many of the residents of Kashmere Gardens are still in danger. Piles of rubble sit in front yards, creating ideal breeding grounds for mosquitoes that spread Zika, dengue, and West Nile viruses. Lingering mold infestations trigger asthma and other respiratory conditions. And those few residents with the resources to rebuild are living in homes under active renovation, exposing themselves to a cocktail of airborne carcinogens released by paint, waterproofing sprays, and other building materials.

Like it or not, we humans are facing a new normal: In January, the National Oceanic and Atmospheric Administration announced that the last four years were the warmest on record—and global temperatures are projected to continue climbing. While much attention has been focused on ice caps, glaciers, deserts, and other sparsely inhabited regions, life in our most densely populated places will also be dramatically altered. Expanding cities, their growth fueled by global rural-to-urban migration, emit higher levels of climate-altering pollution, which in turn warms the atmosphere and causes dangerous stresses on public health.

“For city dwellers, climate change poses a very specific set of public health challenges,” says Ashish Jha, K.T. Li Professor of Global Health and director of the Harvard Global Health Institute at the Harvard T.H. Chan School of Public Health. “Cities are usually near bodies of water, on rivers, or near the ocean. As climate warms, you’re going to have serious issues with extreme storms and flooding, which can expose residents to dangerous chemicals and infectious disease. You’re also going to have to deal with extreme heat, which can cause cardiovascular and respiratory stress. There’s more and more evidence that climate change is directly contributing to public health problems in urban areas.”

But cities are also living laboratories for climate change solutions. And some experts say that if climate change is not solved in cities, it won’t be solved at all. “Urban areas hold more than half the world’s population and most of its built assets and economic activities. They also house a high proportion of the population and economic activities most at risk from climate change, and a high proportion of global greenhouse-gas emissions are generated by urban-based activities and residents,” notes a 2014 report from the Intergovernmental Panel on Climate Change (IPCC). “Action in urban centers is essential to successful global climate change adaptation.”

In 1990, the United Nations (U.N.) Department of Economic and Social Affairs identified only 10 “megacities” with populations larger than 10 million people. By 2014, more than 28 cities around the globe had hit that benchmark, collectively housing 54 percent of the world’s urban population. “For the first time in human history, the majority of our species lives entirely in cities,” Jha says. “The best prediction is that we’re going to be 70 percent urban by 2050 or 2060.”

When cities grow, they inevitably burn more fossil fuels in vehicles and electricity production, generating equally formidable amounts of greenhouse gases, which trap heat in the atmosphere. As the U.N. Human Settlements Programme notes, urban areas worldwide are responsible for up to 80 percent of the planet’s CO2 emissions. With megacities on the rise, that proportion could go up, accelerating climate change.

Increasing global temperatures put coastal cities in particular at risk. In 2009, the IPCC predicted that extra atmospheric heat would cause a rise in average sea level of between 18 and 38 centimeters (roughly 7 and 15 inches) over the next 100 years—its best-case estimate. If the atmosphere warms by more than 2 degrees Celsius (3.6 degrees Fahrenheit), the panel noted, sea levels worldwide could rise as much as 59 centimeters (about 23.2 inches).

Pair that with a direct hit from a powerful hurricane or cyclone, and entire sections of low-lying megacities like Bangkok, Thailand, and Mumbai, India, could be swamped. Major infrastructure from roadways to utilities could be overwhelmed and hospitals inundated. With little access to drinking water, sanitation, transportation, or reliable health care, millions of people could be at risk from the unchecked spread of infectious disease.

The rate at which many coastal cities are expanding makes the problem acute, says Ronak Patel, founder and director of the Urbanization and Resilience Program at the Harvard Humanitarian Initiative. “These cities are growing in a way that leaves them unable to respond to climate threats,” he says. “Their resilience is lower, in part, because their baseline public health infrastructure is poor.”

Worldwide, rising temperatures in dense urban areas will worsen existing public health dangers. When temperatures soar, emissions often increase as well, says Shahir Masri, SD ’16, who studies air quality and epidemiology at the University of California, Irvine. On hot days, power plants—many of which burn fossil fuels—must meet increased demands, spewing hazardous levels of particulates and ozone into the air. “When you get superhot temperatures, you’ve got way more people that are going to be shutting their doors, putting on their ACs, and exacerbating air pollution,” Masri says.

Sunlight and heat can then “cook” pollution emissions, converting them into even more harmful products such as ozone gas, which can cause asthma and lung damage. Once formed, ozone can produce tiny “ultrafine” particulates smaller than 2.5 microns across (PM2.5), which end up deep in the lungs, contributing to inflammation and cardiovascular disease.

And high temperatures themselves are a major health issue, notes Augusta Williams, SD ’19, in the Environmental Health Department at the Harvard Chan School. “Many people don’t realize it, but heat is kind of a silent threat,” she says. “It’s actually responsible for more deaths than hurricanes, tornadoes, or floods. Heat influences cardiovascular disease, respiratory and renal problems, even mental health status.”

Hot air and intense sunlight also produce “urban heat islands” amid tightly clustered buildings. “When you have greater density of buildings made out of materials like concrete and asphalt, those materials absorb heat on warm days, then reradiate heat back out. It can create temperatures up to 10 degrees Fahrenheit warmer than the surrounding area,” says Williams. Since many existing building materials retain that heat, temperatures within them can stay high for hours after the sun sets, she adds. “When people and buildings are not able to cool down during the overnight hours, it exacerbates heat exposure during heat waves,” she says.

Changing climate is also amplifying human migration worldwide, causing a massive movement into cities. Most migrants are relocating from rural areas for economic or humanitarian reasons, says Michael VanRooyen, Lavine Family Professor of Humanitarian Studies at the Harvard Chan School and director of the Harvard Humanitarian Initiative. In some cases, these people can no longer make a living from subsistence farming, due to changing rainfall and heat that withers crops. In other cases, they’re fleeing conflicts caused by dwindling natural resources. Either way, he says, climate drivers can be an important contributor.

The ongoing war and public health catastrophe in Syria, VanRooyen notes, may have been at least partially precipitated by a massive drought in rural areas that stirred migration and caused widespread civil unrest. A similar story has unfolded over decades in Darfur, southwest Sudan, as seasonal monsoons that the region historically relied on for water began to vanish. Suddenly, groups of nomadic herders and settled farmers that coexisted for centuries were forced to compete for limited food and water sources. When the Sudanese government sought to eliminate the Darfurian tribes, hundreds of thousands of people were killed in the ensuing bloodshed.

“Vulnerability to climate-related disasters is all about location, location, location,” VanRooyen says. Each year, an average of 2.3 million people are displaced by natural hazards, with the majority of displacements in low- and middle-income countries. Once migrants make it to a city, those without financial means settle into the only places they can afford: massive shantytowns and urban slums.

Ronak Patel notes that residents of these informal urban settlements are being squeezed on both ends. As shifting weather devastates rural agriculture, it also chokes off the major food source for most cities, triggering hikes in food prices. In 2009, for example, the World Bank food index reported that the cost of staple foods like maize and wheat in central Africa had jumped by more than 70 percent, causing undernourishment in 763,000 people.

Waves of climate-related migration in Africa and the Middle East could be replicated in other regions of the world, says Aaron Bernstein, associate director of the Center for Health and the Global Environment at the Harvard Chan School.

In the Andes Mountains of South America, tropical glaciers that provide water for millions of people downstream have shrunk by 22 percent since 1970. The melting rate is getting faster as global temperatures warm—and if the glaciers were to disappear entirely, it could cause widespread water shortages in the region.

Ultimately, the biggest impact that changing climate may have on public health is that it will make existing problems far worse. In the developing world, many governments already struggle to provide basic sanitation or health care for millions of their poorest residents. On normal days in Cape Town, South Africa, for example, 400,000 residents—more than 10 percent of the population—live in neighborhoods without electricity, running water, or sewage systems. After three years of historic drought, it nearly became the first major metropolis in the world to run out of water entirely.

“In any sort of global perspective, places where climate change is going to be most painful are places where people are poor, places where people live on or near the coast, and places that are at or near sea level,” Bernstein says. “In particular, it may exact its heaviest toll in poorer countries, where the health of many may already be compromised and the resources to adapt are scarcest.”

As the world faces rising seas, a warming atmosphere, and vast changes in weather, it’s easy to be pessimistic about the future. Short of eliminating greenhouse-gas emissions, real solutions are off the table. Instead, our future will need to involve both mitigating climate change by reducing its core causes (as some put it, “avoiding the unmanageable”) and adapting to existing threats by coming up with new strategies to reduce population impact (“managing the unavoidable”).

Major polluters like China, which is responsible for almost 30 percent of the world’s greenhouse-gas emissions, have already laid out plans to generate half of new power needs with renewable sources by 2020. In the U.S., despite rollbacks of federal environmental regulations under the Trump administration, the governments of cities, counties, and states have stepped up to create emissions controls of their own. In all these instances, adaptation and mitigation will require focusing on a few key areas.

1. Reframe climate action as public health action

Instead of spending extra money to “go green” for the sake of the environment, municipalities could position climate mitigation as a means of improving public health, says Bernstein. “If we make the argument that dealing with climate change is about protecting the health of the American people—and we can make that argument—we will succeed at decarbonization,” he says. “When it comes to paying for better health, we Americans are willing to spend. We’re already spending 18 percent of GDP on health care. But wouldn’t it be better to spend that money to keep people healthy, rather than to treat them when they’re already sick?”

2. Bolster health care infrastructure

To become more resilient in the face of climate change, cities will need to shore up major health care centers. “People still assume that when a disaster strikes or when a severe storm occurs, hospitals will be open for them if they get sick or injured. But increasingly, as we see larger storm surges, heavier precipitation, extreme wind and heat, the chance that health care facilities will be taken offline by these events increases substantially,” says Paul Biddinger, director of the Emergency Preparedness and Response Exercise Program at the Harvard Chan School and medical director for emergency preparedness at Partners HealthCare.

When Hurricane Sandy struck New York in 2012, he notes, Bellevue Hospital—the largest care center in Manhattan—pumped more than 17 million gallons of water from its basement. Yet even that Herculean effort wasn’t enough: The flood eventually inundated fuel pumps that fed backup generators on higher floors. The hospital’s electrical supply shut down entirely, leaving staff scrambling to provide care for patients relying on ventilators, heart monitors, and other machinery. Hundreds of patients and caregivers had to be evacuated.

Memorial Medical Center in New Orleans faced an eerily similar fate during Hurricane Katrina in 2005, Biddinger notes. Although emergency generators initially kept the hospital running for more than 48 hours after the storm, floodwaters eventually overwhelmed them, knocking out backup power. In the rush to evacuate, 11 patients died.

As climate change continues to produce violent storms like Sandy, Biddinger says, it will become essential to make cities’ health care centers structurally resilient. “In Boston, hospital buildings are typically built for many, many decades of expected use,” he says. “We are designing our future construction with climate change in mind. Utility services are more protected, more elevated, and more shielded from flooding and from high winds.”

3. Improve resilience in resource-poor settings

In developing countries, even relatively simple interventions can improve public health in the face of changing climate, says Michael VanRooyen. The Philippines, he notes, is a nation regularly hit by powerful typhoons—yet through leadership on a mayoral level, small towns across the nation are reducing the effects of those storms on residents.

“One way to build resilience is to educate local leadership about preparation—how to participate in early- warning systems and planned evacuations, how to store equipment and supplies for people who have to be evacuated, how to build resilient structures so that they don’t get washed away. So even in places that are economically underdeveloped, there are a lot of strategies that can be learned from one town to the next to the next to the next to help their population prepare,” VanRooyen notes.

Bangladesh offers another example of simple, low-tech solutions to climate-based health issues. Since much of the countryside is barely above sea level, constructing elevated concrete storm shelters—and conducting early-warning drills and exercises—have saved hundreds of thousands of lives during extreme flooding.

“The death rate from major storms has plummeted, because people have learned to adapt and plan, and in so doing become resilient,” VanRooyen says. “Even at a very basic community level, people are aware of the possibility of storms and play a significant role in planning for it. Those planning efforts really do save thousands and thousands of lives. So even though the number and the severity of storms in Bangladesh, the Philippines, and elsewhere have increased, the number of deaths has rapidly decreased just because of planning and community-based strategies.”

4. Plant urban forests

Green spaces outside buildings make a major difference in how heat is perceived, says Linda Powers Tomasso, a PhD student in environmental health at the Harvard Chan School. As urban areas grow at a breakneck pace, creating urban forests and parklands in cities will enable residents to cope with sweltering summers through temperature and moisture regulation.

“Forested green spaces absorb the heat into the ground. If we pave over these areas, we’re converting them to places that release heat instead. Cities that are heavily paved over can be much hotter, even by 10 degrees than more verdant tracts of land,” says Tomasso. “For those who access nature on a regular basis, there’s also a health benefit of exposure to green space in terms of cognition, mood, and physiology, such as lower levels of stress, lower blood pressure, enhanced focus, and creativity.”

Tomasso is part of a Harvard Chan team that is studying how to better incorporate green space into a major development in Bangkok. In an abandoned rice paddy on the outer edges of the city, developers are planning a multigenerational living space that will be made up of at least 35 percent vegetation, about a third of which will be restored forest. “When you’re talking about a city, that’s a pretty generous amount. But it helps with storm water management and cyclical flooding while also delivering nature-based health benefits,” she says.

5. Think locally, act locally

These localized solutions may be the front lines for dealing with the effects of changing climate. “Nation-states were the organizing principle of public health in the 20th century. Cities are going to be the organizing principle for health in the 21st century,” says the Harvard Global Health Institute’s Ashish Jha. “They will take on a bigger and bigger role in public health. And much of that will involve thinking hard about how to mitigate the harmful effects of climate change.”

Cities, he adds, are generally far more nimble than national governments—and potentially more responsive to the problems of climate change, since any adaptations will be tailored to local conditions. That means that even on the neighborhood level, residents will play a major role in how their communities respond to environmental threats.

“Democracy is a bottom-up approach. You’re supposed to manage your issues locally,” says Gina McCarthy, former administrator of the U.S. Environmental Protection Agency, now professor of the practice of public health and director of the Center for Health and the Global Environment at the Harvard Chan School. “Maybe to everybody in Washington, climate change is a large national or global problem, but to people in a local community, their sewer is always overflowing because it can’t handle the high-intensity storms, or they have a drought and their farms are drying up. The public health sphere has always been local. That’s where innovation often starts. That’s where creative approaches begin.”

David Levin is a science writer based in Boston.