How Climate Changes Impact Microbes

Written by Emma Loewe: Writer, author, and editor of Cultured. Her writing explores the intersection of nature, climate, and human health. Emma is the author of “Return to Nature” and “The Spirit Almanac.”
Reviewed by Jennie O’Grady: Senior SciComms Specialist at Seed Health

When you picture the damage of climate change, you might imagine communities underwater or forests ablaze. But at the same time, climate change spurs microscopic shifts that are unseen but far from unfelt.

Threats like extreme heat, biodiversity loss, and air pollution are now destabilizing the microorganisms within and around us. Let’s explore the microbial footprint of climate change, why it matters to public health and safety, and how we can use it to adapt to an unknown future. 

The Microbial Impact of Climate Changes

Extreme Heat:

If you are in Southern California, Italy, or Western Canada at the time of this writing, chances are, you’re sweating. These are just a few places where forecast temperatures are currently hotter than normal.¹ This summer was the hottest ever recorded (again) and this year will likely become the hottest on record (also again).^2,3 This extreme heat predisposes us to cardiorespiratory diseases, mental health issues, and adverse pregnancy and birth outcomes, and it has far-reaching impacts on our microbial compositions as well.^4,5,6

Our bodies provide the scaffolding upon which communities of microscopic organisms (bacteria, viruses, fungi, etc.) can grow and flourish. The most expansive and well-studied of these microbial ecosystems resides in the gut—and it’s threatened by persistent heat exposure.

Research shows that heat stress is associated with a decline in Firmicutes, a phylum of beneficial bacteria in the gut that are short-chain fatty acids (SCFA) producers.⁷ Without these SCFAs, the gut’s protective barrier can weaken, potentially predisposing us to inflammation and disease over time. Furthermore, heat stress’s negative impact on the gut microbiome may disrupt immune function, metabolism, and gut-brain axis communication with broad health implications for humans and animals alike.⁸

Heat also impacts the microorganisms in our environment that help shield us from some of the worst impacts of climate change via carbon dioxide fixation (taking CO₂ from the atmosphere and converting it into organic compounds). 

Marine phytoplankton (microscopic plants in the ocean) are responsible for about half of the CO₂ that is removed from the air through photosynthesis, the process plants use to turn sunlight into energy. In this way, they help absorb large amounts of greenhouse gases (similar to how trees and plants on land do). Warmer temperatures seem to decrease the growth rate of these important climate change mitigators.^9,10 On land, warming threatens various fungi and Actinobacteria in the soil microbiome, negatively affecting its ability to sequester carbon and grow nutrient-rich food.¹¹

Biodiversity Loss:

If you feel like there are fewer fireflies, butterflies, or other critters now than when you were growing up, you’re onto something. Human activity has significantly increased extinction rates and we are now losing some species up to 100 times faster than expected.^12,13 

At the same time, the abundance of some vital microscopic life forms is also declining while less desirable bacterial families like Geodermatophilus (typically desert bacteria) and Streptomyces mirabilis (spore producers that show antibiotic resistance) may be getting more abundant.^14,15 Underwater, ocean acidification (the result of increasing CO₂ levels in the atmosphere) is shifting the communities of bacteria on corals, bivalves, and seagrasses, leaving their hosts more vulnerable to disease.¹⁶ 

You might be thinking: We’re losing some of the world’s bacteria and fungi—so what? Well, microorganisms form the building blocks of life, allowing plants, animals, and humans to undergo vital biological processes.¹⁴ Without them, there is no us (the foundational concept behind One Health—the idea that people, animals, and the environment are intricately connected and cannot exist without one another).¹⁷ 

As Raquel S. Peixoto, Ph.D., a coral microbiologist and Seed Scientific Board Member, declared in a 2022 perspective paper published in Nature Microbiology: “The stewardship of biodiversity is a collective duty as the planet’s ecosystems are strongly interdependent and the integrity of each of these systems is a necessary condition for sustaining life.”¹⁸ 

Just as having a diverse assembly of bacteria is essential for outcompeting pathogenic species in the gut, microbial diversity in the environment helps protect against invasive species and outside threats. 

Extreme Storms:

Flooding, drought, heavy rains, tropical storms, snowstorms, and hurricanes are all signs of a destabilized climate.¹⁹ These extreme weather events (which continue to become less and less “extreme”) lead to power outages, blocked roads, and property damages that increasingly pull people away from their homes and communities. By the year 2050, there will be an estimated 200 million climate migrants, or ecological refugees, reeling from displacement.²⁰ 

This is sure to take a toll on our bodies, our livelihoods, and our sense of community, not to mention our microbial functioning. Traumatic events that induce depression, anxiety, and stress, like forced relocation, have been associated with microbiome dysbiosis (an imbalance between beneficial and pathogenic microbiota) that can persist for months or longer.²¹

Air Pollution:

Air pollution is complex in that it’s both a cause (industrial greenhouse gas production) and an effect (smoke and chemical release from wildfires) of our changing climate.

On the one hand, accruing pollutants like CO₂ are known to reduce the growth and nutrient-cycling capabilities of plant-associated soil microbes. By shifting soil microbial community structure, metabolism, and diversity, atmospheric carbon dioxide also threatens our ability to grow nutritious food in the future.²²

Pollutants from industrial sources, transportation, and wildfires also affect the air we breathe in unexpected ways.²³ Not only does living in a more polluted area increase our risk of lung and heart disease, but research suggests that polluted air also has a different “aerobiome” (the collection of microorganisms in airspace), and breathing it may reduce the diversity and resilience of our gut microbiomes.^24,25,26 Over time, it may also increase our risk of developing obesity and type 2 diabetes.²⁷

We still have a lot to learn about the aerobiome (this is only the second year that researchers have studied it in earnest), but it seems to be yet another reason to treat air pollution as a major public health threat.²⁸ 

Pathogenic Disease Spread:

Research shows that the various biological, ecological, environmental, and social factors resulting from climate change can aggravate pathogenic infectious diseases.²⁹ The widespread movement of species in response to climate change brings people in contact with new infectious sources—which, when combined with strengthened pathogens and weakened immunity also caused by climate shifts, can worsen disease spread.

This is amplified by the fact that climatic changes make previously inhospitable areas more suitable for warmth and humidity-loving mosquitoes, ticks, and other vectors that carry disease. As these critters expand their latitude and altitude ranges, experts predict that the parasites, bacteria, and viruses they carry will pose a greater health threat to humans and other species around the world.³⁰ There is also some potential that ancient microorganisms trapped in ice and frozen ground (permafrost) will escape as temperatures warm and ice melts, possibly exposing us to long-dormant diseases.³¹ 

Can We Do Anything About It?

Climate changes affect so many elements of our world—from the macro to the micro. This is, of course, worrying. But it’s also empowering. If microorganisms are part of the problem, that means they can also be leveraged for solutions.

Researchers around the world are now designing microbiome-based interventions to climate change such as probiotics that can repopulate coral reefs and bacterial innovations that can trap carbon dioxide emissions. 

You, too, can get involved in this microbial stewardship. The first step is tending to your microbial world within to feel more energized and clearheaded. From there, you’ll be better equipped to take positive environmental action. Here are some microbe-inspired tips for every Earth dweller:

• Protect your microbial world: Tending to your body’s innate biodiversity can help you remain strong and resilient in any environment. Be wary of products or solutions that intend to “wipe out” bacteria (such as antibiotics), only taking them if deemed necessary by your doctor. Limiting alcohol, highly processed foods, and sedentary behaviors as much as possible can also preserve microbiome diversity.
• Rewild your ecosystem within: Beyond protecting the microbial diversity you already have, you can also take steps to expand upon it—essentially “rewilding” your internal ecosystem. Some ways to do so include eating a diversity of fruits, vegetables, and high-fiber foods, getting your hands dirty and exploring biodiverse natural environments, and taking a probiotic formulated with strains that have been clinically studied for an intended benefit. 
• Don’t brush aside climate emotions: Living through climate change can lead to a wide array of emotions—from solastalgia (the distress of watching familiar landscapes change) to eco-guilt (the feeling that you’re not doing enough to make a difference).^32,33,34 Instead of pushing these emotions away, do your best to feel and process them in real time—before they can harm your mental (and microbial) health. Seeing a therapist who is literate in climate emotions or finding a third space where you can talk them through your feelings in community may help. 
• Engage with community science: You don’t need to have a Ph.D. to locate microbial solutions to climate challenges; Non-researchers can take part by signing up for community science projects. These are open calls for anyone who wants to collect samples in their area in order to be analyzed and leveraged for science. To find opportunities near you, check out CitSci.org, CitizenScience.gov, SciStarter, and SeedLabs, Seed’s environmental research division.

The Key Insight

The climate is changing and so are we. The human microbiome is a microcosm of the planet’s microbiome, and both are being altered by extreme heat, unpredictable storms, pollution, and biodiversity loss. Protecting the unseen organisms within and around us is a climate action all its own—a micro step that can have macro impacts.