01 Jun 2010: Analysis
The Microbe Factor and
Its Role in Our Climate Future
Within the planet’s oceans and soils are trillions of bacteria that store and release far more carbon dioxide than all of the Earth’s trees and plants. Now, scientists are attempting to understand how the world’s bacteria will influence — and be influenced by — a warming climate.
When new reports about global warming come out, they typically include a picture of the land and sky, with arrows marking the movement of carbon dioxide around the planet. Some arrows rise up from cities and farmland, while other arrows plunge down to forests and oceans. This sort of diagram does a great job of illustrating the big picture. Thanks to human activity, carbon dioxide is rising into the atmosphere faster than the planet can draw it down. But the giant scale of this picture hides some of the most important players in the global warming story, which are as crucial to the future of the planet as factories and forests: the planet’s vast swarms of microbes.
A single bacterium, measuring a few millionths of an inch across, may not seem like much compared to a coal-fired power plant. But taken together, microbes are a force to be reckoned with. Some scientists estimate that our planet is home to about 5 trillion trillion bacteria They pack the oceans and the soils; they live just about everywhere they can find even a trace of liquid water. Together, microbes lock up — and release — a huge amount of carbon. The world’s soils — the product of bacteria and fungi breaking down plant matter — contain more than 2.5 trillion tons of carbon. “If you look at all the trees and the grass and the flowers and add all that up, there’s four times as much carbon in the soil,” says Steven Allison, a biologist at the University of California at Irvine.
Even more impressive is the vast amount of carbon that microbes pump around the biosphere. On the surface of the ocean, photosynthetic bacteria
Microbes have been absorbing and releasing greenhouse gases since they evolved 3.5 billion years agosuck vast amounts of carbon dioxide dissolved in the water and turn it into organic molecules. The ocean is also rife with bacteria that feed on organic matter and release carbon dioxide as waste. Meanwhile, the microbes that break plant matter into soil release 55 billion tons a year of carbon dioxide. “It’s eight times what humans are putting into the atmosphere through fossil fuel burning and deforestation,” says Allison.
Microbes have been absorbing and releasing greenhouse gases ever since they first evolved in the ocean more than 3.5 billion years ago and spread on land about 2 billion years ago. And in the process they’ve influenced the Earth’s climate. But the influence doesn’t just flow one way, from microbes to the climate. As the climate changes, it can change the planet’s microbial menagerie.
Scientists are only just starting to figure out some of the rules that govern this feedback. They know just enough to recognize that as we raise the planet’s temperature, we will alter the planet’s microbes. And as we change the world’s microbes, we will also change their impact on the climate. But scientists have only a rough sense of what those changes will turn out to be. It’s possible that we will cause bacteria to churn out greenhouse gases far faster than they do today, adding to our own global warming.
Wikimedia Commons
A microscopic view of oscillatoria, a bacteria found in freshwater.
To see the starkest evidence of the feedback between global warming and microbes, you need only travel to the Arctic. The tundra is a tough place for microbes to make a living. They are frozen for much of the year, and the stress of the cold makes them grow poorly even in warm months. Making life even harder for them is the lack of oxygen in the boggy ground. When tundra plants die, microbes can only break down a fraction of their biomass. The rest becomes entombed in permafrost.
The tundra of North America and Siberia has been storing away carbon for the past 11,000 years, since the glaciers retreated at the end of the last Ice Age. But as the Arctic has warmed in recent decades, the flow of carbon has reversed: The tundra has started releasing more carbon than it captures. Scientists believe that the change has come as rising temperatures in the Arctic have reduced the stress experienced by the microbes. The tundra has also become drier, so that oxygen can penetrate into the ground, allowing microbes to thrive. Decomposing microbes can now feed on the dead plant matter and pump carbon into the atmosphere.
Scientists would like to know what those microbes will do if we continue to shoot more carbon dioxide into the atmosphere. It’s possible, for example,
We believe that as the polar ocean warms, the ecosystem will change to favor microbes,” says one researcher.that microbes could accelerate the pace of climate change. As the Arctic warms and dries, microbes release carbon dioxide into the air. The carbon dioxide drives up temperatures, causing the tundra to warm and dry even more. The microbes are spurred to grow faster and release still more carbon dioxide. With so much carbon locked up in the world’s permafrost, the possibility of such a runaway feedback is sobering.
The microbes in the polar oceans may behave in a similar way, although for different reasons. Hugh Ducklow, director of the Ecosystems Center at the Marine Biological Laboratory in Woods Hole, Mass., and his colleagues have found that marine microbes eat only a small fraction of organic matter. The rest gets devoured by small animals or sinks down into the deep ocean. As polar oceans warm, however, Ducklow suspects that marine microbes will become more active and devour more organic matter. “We believe that as the polar ocean warms, the ecosystem will change to favor microbes,” says Ducklow.
As the microbe population grows, it will release more carbon dioxide into the water. The oceans will thus be able to absorb less carbon dioxide from the atmosphere. As a result, the carbon dioxide levels in the atmosphere will climb, warming the planet. “The effects of climate change on the oceans are a bit like what’s happening in the tundra,” says Ducklow, “but the mechanisms and timescales are very different.”
On land and at sea, however, microbes are influenced by lots of different factors. In the ocean, global warming will
It’s possible that there are rare species of microbes that will thrive in warmer temperatures.also change the pH of seawater and the wind patterns, both of which could either slow the growth of microbes or accelerate it. Likewise, in the tundra, the warmer temperatures are allowing trees and shrubs to advance northward, and the shadows they cast on the ground may influence microbes in unpredictable ways.
To tackle this complexity, some scientists are developing sophisticated computer models. Allison and his colleagues recently constructed a model of the microbes living in the soil of temperate forests. The model tracked the growth of bacteria as they fed on carbon in the soil, along with the carbon dioxide they released into the atmosphere. The scientists then raised the temperature of their virtual forest 5 degrees Celsius and observed how it changed.
The bacteria experienced stress in the warmer climate, and as a result their biochemical reactions ran less efficiently. Instead of converting much of the carbon in plants into their own biomass, the microbes released more of it as carbon dioxide.
You might think that the hotter temperatures would therefore lead to more carbon dioxide in the air. But because the bacteria became inefficient, their growth slowed down. So there were fewer bacteria to release carbon dioxide.
MORE FROM YALE e360
Network Theory: A Key to
Unraveling How Nature Works
READ MORE
Allison stresses that his model is just a first stab at understanding the complex changes that will come to the microbial world. For one thing, it only applies to temperate forests. “Our model doesn’t apply to the tundra at all,” he says, pointing out that warming the tundra reduces the stress on bacteria, because they’re so cold to start off with. He expects that his model would show the tundra releasing more carbon.
Such models assume that bacteria stay the same as the climate changes. But communities of microbes change a lot, over days, months, and years. It’s possible, for example, that there are rare species of microbes that will turn out to thrive in the warmer temperatures. It’s also possible that global warming will drive microbes to evolve. Albert Bennett, Dean of the School of Biological Sciences at the University of California, Irvine, has run experiments in which he has reared flasks of E. coli while steadily raising the temperature. After just a few hundred generations, the bacteria evolved to grow faster at the higher temperature than at their original temperature. We may be running the same experiment on a planetary scale.
“We don’t understand if they can adapt, or how fast they can adapt,” says Allison. “It’s now our job as scientists to figure out which is going to be the case.”
POSTED ON 01 Jun 2010 IN Climate Climate Oceans Science & Technology Science & Technology North America
Comments have been closed on this feature.
ABOUT THE AUTHORCarl Zimmer writes about science for The New York Times and a number of magazines. A 2007 winner of the National Academies of Science Communication Award, Zimmer is the author of six books, including Microcosm: E. coli and the New Science of Life. In previous articles for Yale Environment 360, he has written about the prospect of a warming world causing an evolutionary explosion and about using assisted migration to save species threatened by climate change.
Recommend
Tweet
Reddit
Email
Print
Stumble Upon
ShareRELATED ARTICLES
A Summer of Extremes
Signifies the New Normal
This summer has seen record heat waves and wildfires in the U.S, the worst flooding in Beijing’s modern history, and droughts that devastated the U.S. corn crop and led India to set up “refugee camps” for livestock. These extreme events were not freak occurrences — this is how the earth works now.
Florida Counties Band Together
To Ready for Warming’s Effects
While U.S. action on climate change remains stalled, four south Florida counties have joined forces to plan for how to deal with the impacts — some of which are already being felt — of rising seas, higher temperatures, and more torrential rains.
What Rising Temperatures May
Mean for World’s Wine Industry
Warming temperatures associated with climate change are already affecting vineyards from France to Chile, often in beneficial ways. But as the world continues to warm, some traditional winemaking regions are scrambling to adapt, while other areas see themselves as new wine frontiers.
The Long Strange Journey
Of Earth’s Traveling Microbes
Airborne microbes can travel thousands of miles and high into the stratosphere. Now scientists are beginning to understand the possible role of these microbes — such as bacteria, fungal spores, and tiny algae — in creating clouds, causing rain, spreading disease, and even changing climate.
The World’s Tropical Forests
Are Already Feeling the Heat
Much attention has been paid to how global warming is affecting the world’s polar regions and glaciers. But a leading authority on tropical forests warns that rising temperatures could have an equally profound impact on rainforests and are already taking a toll on some tropical species.
MORE IN Analysis
Will Huge New Hydro Projects
Bring Power to Africa’s People?
A giant new hydro project on the Congo River is only the latest in a rush of massive dams being built across Africa. Critics contend small-scale renewable energy projects would be a far more effective way of bringing power to the hundreds of millions of Africans still without electricity.
Research on Microbes Points
To New Tools for Conservation
Improvements in DNA technology now make it possible for biologists to identify every living organism in and around a species. Scientists say this could have profound implications for everything from protecting amphibians from a deadly fungus to reintroducing species into the wild.
True Nature: Revising Ideas
On What is Pristine and Wild
New research shows that humans have been transforming the earth and its ecosystems for millenniums — far longer than previously believed. These findings call into question our notions about what is unspoiled nature and what should be preserved.
Probing the Reasons Behind
The Changing Pace of Warming
A consensus is emerging among scientists that the rate of global warming has slowed over the last decade. While they are still examining why, many researchers believe this phenomenon is linked to the heat being absorbed by the world’s oceans.
Blocked Migration: Fish Ladders
On U.S. Dams Are Not Effective
Fishways on rivers in the U.S. Northeast are failing, with less than 3 percent of one key species making it upriver to their spawning grounds, according to a new study. The researchers’ findings provide a cautionary tale for other nations now planning big dam projects.
The Scientist as Guardian:
A Tool for Protecting the Wild
An expanding body of evidence shows that the presence of field biologists and their assistants is playing an important part in deterring poaching, illegal logging, and other destructive activities in the world’s parks and wildlife reserves.
Giant Sequoias Face Looming
Threat from Shifting Climate
The world’s largest living species, native to California’s Sierra Nevada, faces a two-pronged risk from declining snowpack and rising temperatures. The threat to sequoias mirrors a growing danger to trees worldwide, with some scientists saying rapid warming this century could wipe out many of the planet’s old trees.
Biodiversity in Logged Forests
Far Higher Than Once Believed
New research shows that scientists have significantly overestimated the damage that logging in tropical forests has done to biodiversity, a finding that could change the way conservationists think about how best to preserve species in areas disturbed by humans.
Will Reform Finally End The
Plunder of Europe’s Fisheries?
Maria Damanaki, Europe’s crusading fisheries minister, is making major headway in changing a cozy, “old boys” network that over-subsidized the European fishing industry and brought about the severe overfishing of the continent’s marine bounty.
Mercury’s Silent Toll
On the World’s Wildlife
Scientists are only beginning to understand the impacts of mercury contamination on birds, fish, and other wildlife populations. But what they are finding is alarming — even low levels can cause harm, and chronic exposure has unexpected and troubling effects.
RELATED e360 DIGEST ITEMS
17 Jun 2013: Changes in Jet Stream Triggered
Record Greenland Melt in 2012, Study Says
10 Jun 2013: Carbon Emissions Increased
1.4 Percent in 2012, IEA Reports
07 Jun 2013: New Map of Antarctica Provides
Clearest Glimpse of Subglacial Continent
30 May 2013: Nuclear Power Has Prevented
1.84 Million Premature Deaths, Study Says
23 May 2013: China Poised to Launch
Much-Anticipated Carbon-Trading Project
21 May 2013: Large Majority of Americans
Believe Global Warming Should be a Priority
16 May 2013: Scientist’s U.S. Road Trip
Reveals Unexpected Methane Emissions
15 May 2013: Glaciers on Everest Disappearing
As Temperatures Rise, Snowfall Declines
14 May 2013: Interview: Climate Pioneer’s Son
Ponders a Worrisome CO2 Milestone
13 May 2013: Project Looks to Quantify
Power Emissions Through Crowdsourcing
Yale Environment 360 is
a publication of the
Yale School of Forestry
& Environmental Studies.
SEARCH e360
CONNECT
Twitter: YaleE360e360 on Facebook
Donate to e360
View mobile site
Bookmark
Share e360
Email newsletter
Subscribe to our feed:
ABOUT
About e360Contact
Submission Guidelines
Reprints
e360 PHOTO GALLERY
South African photojournalist Adam Welz documents the harrowing relocation of six white rhinos to a region that has lost all its rhinos to poaching. View the gallery.
DEPARTMENTS
OpinionReports
Analysis
Interviews
e360 Digest
Podcasts
Video Reports
TOPICS
BiodiversityBusiness & Innovation
Climate
Energy
Forests
Oceans
Policy & Politics
Pollution & Health
Science & Technology
Sustainability
Urbanization
Water
REGIONS
Antarctica and the ArcticAfrica
Asia
Australia
Central & South America
Europe
Middle East
North America
e360 VIDEO
A Yale Environment 360 video explores Ecuador’s threatened Yasuni Biosphere Reserve with scientists inventorying its stunning forests and wildlife. Watch the video.
e360 MOBILE
from Yale
Environment 360 is now available for mobile devices at e360.yale.edu/mobile.
e360 VIDEO
In a Yale Environment 360 video, photographer Pete McBride documents how increasing water demands have transformed the Colorado River, the lifeblood of the arid Southwest. Watch the video.
Top Image: aerial view of Iceland. © Google & TerraMetrics.
e360 VIDEO
The Warriors of Qiugang, a Yale Environment 360 video that chronicles the story of a Chinese village’s fight against a polluting chemical plant, was nominated for a 2011 Academy Award for Best Documentary (Short Subject). Watch the video.
OF INTEREST
