There are questions that worry me profoundly as a population- and environmental-health scientist. Will we have enough food for a growing global population? How will we take care of more people in the next pandemic? What will heat do to millions with hypertension? Will countries wage water wars because of increasing droughts?
These risks all have three things in common: health, climate change and a growing population that the United Nations forecasts will reach 8 billion people around Nov. 15, 2022—double the population of just 48 years ago.
In my 40-year career, first working in the Amazon rainforest and the Centers for Disease Control and Prevention, and then in academia, I have encountered many public-health threats, but none so intransigent and pervasive as climate change. Of the multitude of climate-related adverse health effects, the following four represent the greatest public health concerns for a growing population.Infectious diseases Researchers have found that over half of all human infectious diseases can be worsened by climate change. Flooding, for example, can affect water quality and the habitats where dangerous bacteria and vectors like mosquitoes can breed and transmit infectious diseases to people. Dengue, a painful mosquito-borne viral disease that sickens about 100 million people a year, becomes more common in warm, wet environments. Its R0, or basic reproduction number—a gauge of how quickly it spreads—increased by about 12% from the 1950s to the average in 2012-2021, according to the 2022 Lancet Countdown report. Malaria’s season expanded by 31% in highland areas of Latin America and nearly 14% in Africa’s highlands as temperatures rose over the same period. Flooding can also spread waterborne organisms that cause hepatitis and diarrheal diseases, such as cholera, particularly when large numbers of people are displaced by disasters and living in areas with poor water quality for drinking or washing. Droughts, too, can degrade drinking water quality. As a result, more rodent populations enter into human communities in search of food, increasing the potential to spread hantavirus.Extreme heat Another serious health risk is rising temperatures. Excessive heat can exacerbate existing health problems, such as cardiovascular and respiratory diseases. And when heat stress becomes heat stroke, it can damage the heart, brain and kidneys and become lethal. Today, about 30% of the global population is exposed to potentially deadly heat stress each year. T …