8 billion people: Four ways climate change and population growth are combining to threaten public health, with global consequences | Kiowa County Press

Infectious diseases like COVID-19 top the list of health concerns. Marco Longari/AFP via Getty Images

Maureen Lichtveld, University of Pittsburgh

There are issues that concern me deeply as a population health and environmental scientist.

Will we have enough food for a growing world population? How are we going to care for more people in the next pandemic? What will the heat do to millions of hypertensives? Will countries fight 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 predicts will reach 8 billion people around November 15, 2022, double the population of 2022. barely 48 years old.



In my 40-year career, first in the Amazon rainforest and the Centers for Disease Control and Prevention, then in academia, I have encountered many public health threats, but none as intransigent and pervasive as climate change.

Among 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 more than half of all human infectious diseases can be made worse by climate change.

Flooding, for example, can affect water quality and habitats where bacteria and dangerous vectors like mosquitoes can breed and transmit infectious diseases to humans.

Dengue fever, a painful mosquito-borne viral disease that affects around 100 million people a year, is becoming more common in hot, humid environments. Its R0, or basic reproduction number – a gauge of how quickly it spreads – increased by about 12% between the 1950s and the 2012-2021 average, according to the 2022 Lancet Countdown report. The malaria season has extended by 31% in the highlands of Latin America and by almost 14% in the highlands of Africa, as temperatures have increased over the same period.

Rows of beds, some covered with mosquito netting, fill a warehouse-like space.  Doctors visit with some of the patients.
Patients rest in a makeshift dengue ward at a hospital during a severe outbreak in Pakistan in 2021. Arif Ali/AFP via Getty Images

Floods can also spread waterborne organisms that cause hepatitis and diarrheal diseases, such as cholera, especially when large numbers of people are displaced by disasters and live in areas with poor water. poor quality for drinking or washing.

Droughts can also degrade the quality of drinking water. As a result, more rodent populations are entering human communities in search of food, increasing the potential for hantavirus to spread.

Extreme heat

Rising temperatures are another serious health risk.

Excessive heat can exacerbate existing health problems, such as cardiovascular and respiratory disease. And when heat stress turns into heatstroke, it can damage the heart, brain and kidneys and become fatal.

Today, approximately 30% of the world’s population is exposed to life-threatening heat stress each year. The Intergovernmental Panel on Climate Change estimates that this percentage will increase to at least 48% and up to 76% by the end of this century.

Where climate change affects human health. Centers for Disaster Control and Prevention

In addition to the lives lost, heat exposure is estimated to have led to the loss of 470 billion potential work hours globally in 2021, with associated lost income totaling up to $669 billion. As populations grow and the heat rises, more and more people will rely on fossil fuel powered air conditioning, further contributing to climate change.

Food and water security

The heat also affects the food and water security of a growing population.

The Lancet review found that high temperatures in 2021 shortened the growing season by an average of about 9.3 days for maize or maize and six days for wheat compared to the 1981-2020 average . Warming oceans, meanwhile, can kill shellfish and displace the fisheries that coastal communities depend on. Heat waves in 2020 alone resulted in 98 million more people facing food insecurity than the 1981-2010 average.

A woman standing in a field examines a sorghum stalk
A farmer in Zimbabwe has switched to sorghum, a cereal that can thrive in dry conditions as drought withered other crops in 2019. Jekesai Njikizana/AFP via Getty Images

Rising temperatures are also affecting the supply of fresh water through evaporation and the shrinking mountain glaciers and snowpack that historically allowed water to flow in the summer months.

Water scarcity and drought could displace nearly 700 million people by 2030, according to UN estimates. Combined with growing populations and growing energy needs, they can also fuel geopolitical conflicts as countries face food shortages and compete for water.

Bad air quality

Air pollution can be exacerbated by drivers of climate change. Hot weather and the same fossil gases that warm the planet contribute to ground-level ozone, a key component of smog. It can exacerbate allergies, asthma and other respiratory problems, as well as cardiovascular disease.

Wildfires fueled by hot, dry landscapes add to the health risk from air pollution. Wildfire smoke is loaded with tiny particles that can penetrate deep into the lungs, causing heart and respiratory problems.

Three schoolgirls with backpacks walk in smog along a road while covering their mouths with tissues.
Smog in New Delhi, India is an ongoing problem. The situation deteriorated so badly in 2017 that the city temporarily closed its primary schools. Sajjad Hussain/AFP via Getty Images

What can we do about it?

Many medical groups and experts are working to counter this cascade of negative climate consequences on human health.

The U.S. National Academy of Medicine has embarked on an ambitious grand challenge in climate change, human health, and equity to accelerate research. At many academic institutions, including the University of Pittsburgh School of Public Health, where I am dean, climate and health are integrated into research, teaching, and service.

Addressing the health burden in low- and middle-income countries is essential. Often the most vulnerable people in these countries are the hardest hit by climate change without having the resources to protect their health and environment. Population growth can aggravate these inequities.

Adaptation assessments can help high-risk countries prepare for the effects of climate change. Development groups are also running projects to expand the cultivation of crops that can thrive in dry conditions. The Pan American Health Organization, which focuses on the Caribbean, is an example of how countries are working to reduce communicable diseases and advance regional capacity to counter the impact of climate change.

Ultimately, reducing health risks will require reducing greenhouse gas emissions that cause climate change.

Countries around the world made a commitment in 1992 to reduce greenhouse gas emissions. Thirty years later, global emissions are only beginning to level off and communities around the world are increasingly suffering from extreme heat waves and devastating floods and droughts.

The ongoing UN Climate Change Conference in November 2022 – which I believe does not focus enough on health – can help draw attention to key climate impacts that harm health. As UN Secretary-General Antonio Guterres noted: As we celebrate our progress, “at the same time, it is a reminder of our shared responsibility to care for our planet and a moment to reflect on the points where we still fail to meet our commitments to one another.”

Samantha Totoni, Ph.D. candidate at the University of Pittsburgh School of Public Health, contributed to this article.

The conversation

Maureen Lichtveld, Dean of the School of Public Health, University of Pittsburgh

This article is republished from The Conversation under a Creative Commons license. Read the original article.