“They [microorganisms] also produce and take up methane, carbon dioxide and nitrous oxide on tremendous scales—so that when it comes to controlling global emissions, they can be either friend or foe.”
-Katherine Bourzac, science and technology writer
“In seeking truth you have to get both sides of a story.”
- Walter Cronkite, American broadcast journalist
On December 12, 2023, the United Nations’ annual Climate Change Conference, referred to as COP28, ended. There was substantial controversy about holding this conference in Dubai, United Arab Emirates (one of the world’s ten largest oil producers), but there was little disagreement about the state of the world’s climate emergency—it’s getting worse.
Infectious diseases specialists are well aware that some human pathogens welcome a warmer planet. But far less appreciated is the fact that some microbes can help us deal with the global warming crisis. (See Katherine Bourzac’s Nature article, “Microbiologists at COP28 push for a seat at the climate-policy table.”) In this Germ Gems post, I briefly review the negative impact of climate change on human health, and then mention some extraordinary microbes that may play a positive role in mitigating climate change.
What is climate change? Until 2015, I knew almost nothing about climate change in general and next to nothing about its impacts on human health. Since then, with the help of colleagues in Health Professionals for a Healthy Climate, I’ve been on a steep learning curve. The following is a very brief summary of what I have learned.
Climate change (aka global warming) is caused by greenhouse gases (GHGs) consisting of carbon dioxide, methane, ozone, nitrous oxide, chlorofluorocarbons, and water vapor. (Carbon dioxide and methane are the really bad actors.) GHGs act like the glass walls of a greenhouse – hence the name. Without this greenhouse effect, temperatures would drop to as low as -18˚C (-0.4˚F)—too cold to sustain most life on Earth. But human activities, e.g., using fossil fuels such as coal, petroleum, and natural gas, are changing Earth's natural greenhouse effect by dramatically increasing the release of GHGs. These GHGs block release of heat from Earth’s atmosphere causing global warming, aka climate change.
Climate change is the single biggest threat to human health. It impairs the function of virtually every organ system, including our cardiovascular, cerebrovascular, pulmonary, and neurological systems. (For a recent review, see Dr. Melanie McKell’s August 31, 2023 article, “Health Effects of Climate Change” in Clinical Advisor.)
In 2015, considerable skepticism existed about whether climate change was real. Since then, climate change denial has largely dissipated in no small part because of a large string of natural disasters fueled by global warming, such as flooding, heat waves, wild fires, and drought. According to a recent report, a climate disaster now occurs every three weeks in the U.S. And, worldwide, 2023 is slated to be the hottest year on record.
Climate change fosters many infectious diseases. Global warming expands the geographic range and the length of the breeding season of many insects. As a result, vector-borne infections are having a field day.
In previous Germ Gems posts, I’ve focused mainly on diseases caused by the bad microbial actors—pathogens carried and transmitted by mosquitoes (such as, malaria, dengue fever, and West Nile virus ), ticks (such as, Borrelia burgdorferi, the cause of Lyme disease) and even sandflies which carry the parasite that causes cutaneous leishmaniasis. (See, respectively, June 15, 2022, and November 8, 2023, Germ Gem posts.) But recent studies suggest that the impact of climate change on infectious diseases is far more pervasive than many of us thought.
On August 22, 2022, Nature Climate Change published the article, “Over half of known human pathogenic diseases can be aggravated by climate change.” The infectious disease experts conducting the study examined the medical literature of established cases of illnesses. They found that “58% (that is 218 out of 375) of infectious diseases confronted by humanity worldwide have been at some point aggravated by climatic hazards.”
Turning to the microbial world to curtail damage of climate change. Pathogens, the bad actors among the microbes, are our mortal enemies. They cause undue suffering to our species. But the vast majority of microbes are our intimate friends; they either cause us no harm or, as in the case of those residing in the human microbiome, provide us great benefit. Not surprisingly, the same can be said for the estimated one trillion species of microbes on Earth.
A growing number of microbiologists, physician scientists, and environmentalists share a positive view of germs. (See “Save the microbes to save the planet. A call to action of the International Union of the Microbiological Societies [IUMS],” One Health Outlook, March 6, 2023.) Microbes were even on the agenda at this year’s COP28 where they were “tapped” to protect the planet. (See, scientific reviewer for the American Society of Microbiology Rachel Burkhardt’s article, “Climate Change Experts Tap Microbes to Protect the Planet.”)
Here are just a few examples of what’s recently been discovered:
Bacteria that “eat” methane (a strain of methylotuvimicrobium buryatnese);
Bacteria that can capture carbon (a type of cyanobacteria off the coast of Sicily that “eats carbon dioxide, ‘astonishingly quickly’”);
Key soil microbes involved in carbon sequestration, including mycorrhizal fungi, arbuscular mycorrhizal fungi, Actinobacteria, and Protobacteria;
Microbes that control our pollution, a process called bioremediation; and
Marine microbes, such as phytoplankton, that perform roughly half of the photosynthesis (that miraculous transformation of sunlight into food and oxygen) that occurs on Earth.
The crisis of climate change: danger and opportunity. President John F. Kennedy is quoted as saying: “The Chinese use two brush strokes to write the word ‘crisis.’ One brush stroke stands for danger; the other for opportunity. In a crisis, be aware of the danger—but recognize the opportunity.”
The existential threat of climate change is extraordinarily dangerous. We are in crisis mode. But climate change is also spurring enormous human ingenuity and technological progress. For me, I’m cautiously optimistic, especially now that microbiologists and other scientists are on board. After all, some 3.8 billion years ago, bacteria figured out how to adapt to an absolutely hellish climate; it was the origin of life on Earth. Perhaps today, scientists can harness microbes and put them to work on saving our species from extinction on this planet.