In the summer of 2022, one of the worst monsoons on record turned parts of Bangladesh, a low-lying country in South Asia, into large, muddy lakes. When the heaviness of the floods finally eased, at least 141 people died and millions of others throughout the region were injured, impoverished or displaced. The sheer scale of the destruction made 2022 a leap year, but data from the past few decades suggests that the historic monsoon was part of a larger trend: climate change is making South Asia’s rainy season more intense and inconsistent. Unusually heavy floods hit the region earlier in the year and more often than before – a pattern research shows will continueand aggravateas the planet warms in the years ahead.
A study published last week shows that Bangladesh’s increasing monsoons come with a staggering death toll, both in the immediate aftermath of the flooding itself and, more significantly, in the months that follow. The true extent of the toll has not been fully captured by local officials, aid organizations or the international research community.
The same probably applies to other parts of the world that experience recurring climate disasters. “In the field of climate and health, we often evaluate the health effects of specific acute events because it is easier to account for all the other potential factors that could confound the association,” said Lara Schwarz, an epidemiologist at the University of California, San Diego said. , who was not involved in the study. But a focus on the short term obscures the bigger picture. “Most climate events do not occur just once and are likely to harm vulnerable populations over and over again, over years, decades and generations,” she said.
In the new study, researchers from the University of California, San Diego and San Francisco found that flooding contributed to the deaths of 152,753 infants – defined as children 11 months old and younger – in Bangladesh in the three decades between 1988 and 2017. The researchers used health surveys conducted by the United States Agency for International Development to collect data on more than 150,000 births over the course of 30 years. They compared that data with high-resolution maps of major floods over that period and found a stark difference in mortality risk: there were 5.3 more infant deaths per 1,000 births in flood-prone areas than in non-flood-prone areas. The authors extrapolated from this finding to estimate how many infant deaths could be attributed to flooding in Bangladesh overall over the period they studied.
Infants are a particularly vulnerable subset of the population, and changes in infant health may reflect the prevalence of health issues in the broader population. “Death is the most serious health outcome,” Schwarz said. “The increased risk of infant mortality suggests that populations living in a flood-prone region may also be at increased risk of other adverse health problems such as improper nutrition, water-borne diseases and poor mental health.”
The majority of the deaths were likely linked to three flood-related conditions. The first, diarrheal disease, often spreads when flooding overwhelms local sanitation infrastructure and causes drinking water supplies to become contaminated. Cholera, one of the most common and deadly waterborne bacterial diseases, is a particular concern in poor countries where sanitation infrastructure is underdeveloped. Flooding also contributes to outbreaks of mosquito-borne diseases such as dengue, because standing water creates ample breeding ground for mosquitoes. Finally, flooding turns agricultural fields into swamps and can lead to massive crop losseswhich contributes to existing food insecurity in Bangladesh. Babies are extreme vulnerable to hunger. The Lancet, a leading medical journal that has a annual analysis of the impact of climate change on human health around the world, identified bacterial and vector-borne diseases and malnutrition as major areas of concern.
Drownings and other injuries from the flooding also accounted for a small percentage of the deaths, the study’s authors told Grist. All the health-related risks posed by flooding, from the first drowning to the last case of dengue, are exacerbated by socio-economic factors such as food security, family income, vaccination history, access to medical care and the condition of local infrastructure such as sewage systems and drinking water treatment facilities.
The study’s authors told Grist that their results suggest that the risks of environmental health hazards are shifting as climate change worsens. Government health agencies and researchers often collect information on the immediate public health impacts of a single extreme weather event. But because a warmer world also means a world plagued by more frequent and intense disasters, communities are repeatedly affected by extreme weather. The long-term, cumulative health consequences of events that occur on an annual or sometimes even more frequent basis are not well understood by the scientific community. And as such, the world has a flawed understanding of the true human cost of extreme weather.
“We need to understand this kind of long-term impact in the context of climate change because communities are going to be repeatedly and systematically exposed to these hazards,” said Tarik Benmahria, an environmental health researcher at the University of California, San Diego. one of three authors of the Bangladesh study. “These types of issues used to be exceptional by definition,” he added. “They are no more.”
The method the researchers used to assess the burden of flooding on communities in Bangladesh over several years, Schwarz said, “has the potential to be applied to assess the long-term effects of other climate exposures.” Extreme heat, hurricanes, and drought, to name a few of the environmental disasters exacerbated by climate change, can also have compounding health effects that occur weeks, months, even years after the event occurred. If future research determines how and when these effects occur, it could potentially save lives. “The approach is very relevant to other areas of the world that are vulnerable to recurring climate hazards,” Schwarz said.
