The world is getting warmer; this we know already. The last five years were the warmest ever recorded by the National Oceanic and Atmospheric Administration, and there are plenty of forecasts detailing the devastation that awaits as climate change worsens, from rising sea levels to melting ice caps to unprecedented, extreme weather.
But all that could happen even sooner than predicted, according to new research, because of how the world’s bacteria release carbon into the air. As bacteria and archaea (another class of single-celled microorganisms) adapt to Earth’s hotter and hotter temperatures, they in turn release CO2 at higher rates.
“Many bacteria perform similar metabolism to us—they take in oxygen and ‘breathe’ out carbon dioxide,” Tom Smith, PhD student at Imperial College London and lead author of the paper published Tuesday in Nature Communications, told Fast Company in an email. It turns out that bacteria “breathe” out CO2 at a higher rate when temperatures increase, and since CO2 is a greenhouse gas, those emissions could in turn raise climate temperatures, meaning bacteria will then emit even more CO2, creating, Smith says, “a positive feedback loop.”
It may seem like single-celled organisms shouldn’t be a big concern when we have traffic-clogged streets and cities full of energy-inefficient buildings, but these bacteria are bountiful.
“The major habitats for bacteria are soils, sub-surface sediments and the oceans, but in general they’re everywhere,” says Smith. Experts say that bacteria account for somewhere between 20% to 50% of the total weight of all organisms on Earth, and so they play a significant role in global CO2 production.
Microorganisms have long changed the world’s climate, and been changed by it, according to the National Center for Biotechnology Information. They are the “backbone” of most ecological systems, and since they generate faster than eukaryotes (organisms with cells that contain a nucleus; in other words, all living things besides bacteria and archaea), they also evolve and adapt to environmental changes more quickly. Scientists can look at how climate change is currently affecting microorganisms to see how it may affect other forms of life down the line.
Though scientists have previously studied the role of prokaryotes (as bacteria and archaea are collectively known) on the climate, that exact relationship between temperature, respiration rate and output of CO2 wasn’t clear. For this paper, researchers analyzed data on respiration rate changes by temperature from 482 prokaryote strains, and found that the majority of them ramp up carbon emissions when at higher temperatures to a greater extent than previously thought. This means that current models estimating climate change aren’t taking into account this cycle of bacteria-produced CO2, which will only increase as the Earth gets warmer.
Though the researchers didn’t calculate exactly how much more CO2 these bacteria will release, or how much more the climate will warm because of that effect, they estimated that including this behavior, a new climate change model may show increased carbon production of 5% to 10%. “That doesn’t sound like very much,” Smith says, “but when considering global CO2 output, it could have a large effect.”
“Many models attempting to estimate the impacts of climate change do actually include this sort of effect for organisms which don’t regulate their body temperature (which can be anything from bacteria, to plants, to insects, etc.), but the numbers used in those models have been based on older work that hasn’t directly accounted for bacteria,” says Smith. “However, we found that, compared to [other] organisms, the metabolic rates of bacteria were likely to increase by an even greater amount with temperature…which means that extra CO2 production due to warming has likely been underestimated in these models.”
Just how much the metabolic rates of bacteria increase with temperature was a surprise to Smith, and it’s not just that they produce more CO2 in the short term; as they continue to evolve to higher temperatures over the years, they’ll keep increasing their carbon output. The researchers hope this can be factored in to future models of global warming—such as the ones that the Intergovernmental Panel on Climate Change relies on—so we can better understand the impacts of climate change, and get a clearer picture of what Earth’s future has in store.