Microbial organisms live in dynamic communities that are foundational to life as we know it. This article takes a closer look at how human-mediated climate change could disrupt the structure and function of these essential communities.
Microbes rule the world. They are involved in biogeochemical cycles that sustain most life on earth, they produce a large majority of the oxygen on our planet, and they also degrade a large number of harmful compounds that we generate in our day-to-day lives. These are just a few of the indispensable jobs that microbes do for us every day. I learned this at university while studying marine biology, and it struck me as incredible.
These tiny organisms are really the foundation of life as we know it, which is currently undergoing a major shift because of human-driven climate change. As a microbial ecologist, I now understand that these life-sustaining microbes aren’t invincible and we don’t know much about them or how climate change will impact them.
Discussions around climate change are often centered around extreme weather events, rising sea, and carbon dioxide (CO2) levels. All of these will have negative impacts on the world’s macrofauna and flora: the plants and animals large enough for us to see. The world’s microbes are often left out, even though they form the foundation of many important food webs and biogeochemical cycles 1.
Microbiomes
Within each animal gut and every patch of soil lives a complex community of microbes: the microbiome. Researchers have recently been paying more attention to the effects of climate change on these microbiomes - and for good reason! Two recently published studies have unveiled how extensively climate change is impacting the microbial communities in soil and animals.
Soil microbes are hidden drivers of important terrestrial biogeochemical cycles. They metabolize nutrients within our ecosystem that other living organisms can’t process. The by-products of these microbial metabolisms provide labile (ready-to-use) nutrients that ultimately fuel the food web, allowing plants and animals to prosper. Soil microbes also have the ability to metabolize greenhouse gases such as CO2 and methane, meaning that the microbial community in soils could help reduce the amount of greenhouse gases in the atmosphere. However, that means they also have the potential to become a source of greenhouse gases. Climate models predict that increases in CO2 levels, temperatures, rain and flooding may all result in soil communities releasing more CO2 into the atmosphere than they absorb. Soil would not only become an additional source of CO2, but the changing conditions of the soil would alter its microbial community and further shift life-supporting biogeochemical cycles 2.
The microbial communities associated with animals are also going to feel the negative effects of climate change. Animal microbiomes play vital roles in the health and disease of their animal hosts 3, 4. Recently, a study took a unique approach to investigate how increased temperature would impact an entire ecosystem. Researchers monitored the changes of three different microbial communities in the water surrounding a flowering plant called a bromeliad: 1) the bacteria in the water surrounding the plant; 2) the nearby arthropods; and 3) the bacteria in the gut of tadpoles also living around this aquatic plant. Higher temperatures changed both the community of arthropods and the environmental bacteria surrounding the plant. This ultimately disrupted the intestinal microbial community of the tadpoles and stunted their growth. The authors also pointed out that this dysbiosis - a disrupted intestinal microbiome - leads to an increased risk of disease in animals 5.
The research currently available clearly shows that climate change will disturb all levels of living organisms - big and small. Microbial communities inhabiting soils and animals should be as much of a climate change concern as are rising sea levels and extreme weather events. Increased temperatures can disrupt microbial communities in the soil and cause a cascade of disruptions throughout the food web.
References
1. Cavicchioli, R. et al. (2019) Scientists’ warning to humanity: microorganisms and climate change. Nat Rev Microbiol https://doi.org/10.1038/s41579-019-0222-5
2. Jansson & Hofmockel (2020) Soil microbiomes and climate change. Nature Reviews https://doi.org/10.1038/s41579-019-0265-7
3. McFall-Ngai et al. (2017) Animals in a bacterial world, a new imperative for the life sciences. PNAS Perspectives https://doi.org/10.1073/pnas.1218525110
4. Gilbert, Sapp, & Taupper (2012) A symbiotic view of life: We have never been individuals. Q Rev Biol https://doi.org/10.1086/668166
5. Greenspan et al. (2020) Warming drives ecological community changes linked to host-associated microbiome dysbiosis. Nature Climate Change https://doi.org/10.1038/s41558-020-0899-5
This article was specialist edited by Dr. Jake Wintermute and copy edited by Cassandra Koh.