Magazine of the Harvard T.H. Chan School of Public Health
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.”