Plants Save the Earth from an Icy Doom (w/ Podcast)

Jul 01, 2009
As plants become starved for CO2, rock weathering diminishes. Credit: David Beerling

(PhysOrg.com) -- Fifty million years ago, the North and South Poles were ice-free and crocodiles roamed the Arctic. Since then, a long-term decrease in the amount of CO2 in the atmosphere has cooled the Earth. Researchers at Yale University, the Carnegie Institution of Washington and the University of Sheffield now show that land plants saved the Earth from a deep frozen fate by buffering the removal of atmospheric CO2 over the past 24 million years.

While the upper limit for atmospheric CO2 levels has been a focus for discussions of global warming and the quality of life on Earth, this study points to the dynamics that maintain the lower sustainable limits of atmospheric CO2.

Volcanic gases naturally add CO2 to the , and over millions of years CO2 is removed by the weathering of silica-based rocks like granite and then locked up in carbonates on the floor of the world's oceans. The more these rocks are weathered, the more CO2 is removed from the atmosphere.

"Mountain building in places like Tibet and South America during the past 25 million years created conditions that should have sucked nearly all the CO2 out of the atmosphere, throwing the Earth into a deep freeze," said senior author Mark Pagani, associate professor of geology and geophysics and a member of the Yale Climate and Energy Institute's executive committee. "But as the CO2 concentration of Earth's atmosphere decreased to about 200 to 250 parts per million, CO2 levels stabilized."

This video is not supported by your browser at this time.

The study, published in the XX issue of Nature, looked for a possible explanation They used simulations of the global carbon cycle and observations from plant growth experiments to show that as atmospheric CO2 concentrations began to drop towards near-starvation levels for land plants, the capacity of plants and vegetation to weather silicate rocks greatly diminished, slowing the draw-down of atmospheric CO2.

"When CO2 levels become suffocatingly low, plant growth is compromised and the health of forest ecosystems suffer," said Pagani. "When this happens, plants can no longer help remove CO2 from the atmosphere faster than volcanoes and other sources can supply it."

"Ultimately, we owe another large debt to plants" said co-author Ken Caldeira from the Carnegie Institution of Washington at Stanford University. "Aside from providing zesty dishes like eggplant parmesan, plants have also stabilized Earth's climate by inhibiting critically low levels of CO2 that would have thrown spinning into space like a frozen ice ball."

Co-author David Beerling from Sheffield University adds, "Our research supports the emerging view that should be recognized as a geologic force of nature, with important consequences for all ."

More information: Nature, (doi:10.1038/nature08133)

Source: Yale University (news : web)

Explore further: Images released of shipwreck in San Francisco Bay

add to favorites email to friend print save as pdf

Related Stories

Corralling the carbon cycle

Nov 13, 2008

(PhysOrg.com) -- Scientists may have overcome a major hurdle to calculating how much carbon dioxide (CO2) is absorbed and released by plants, vital information for understanding how the biosphere responds ...

Carbon study could help reduce harmful emissions

Feb 14, 2008

Earth scientists at The University of Manchester have found that carbon dioxide has been naturally stored for more than a million years in several gas fields in the Colorado Plateau and Rocky Mountains of the United States.

Greenhouse gas effect consistent over 420 million years

Mar 28, 2007

New calculations show that sensitivity of Earth's climate to changes in the greenhouse gas carbon dioxide (CO2) has been consistent for the last 420 million years, according to an article in Nature by geologists at Yale and Wesle ...

Recommended for you

NASA sees last vestiges of Tropical Depression Jack

8 hours ago

Tropical Cyclone Jack had weakened to a tropical depression when NASA and JAXA's Tropical Rainfall Measuring Mission (TRMM) satellite passed above on April 22, 2014 at 1120 UTC/7:20 a.m. EDT.

New discovery helps solve mystery source of African lava

11 hours ago

Floods of molten lava may sound like the stuff of apocalyptic theorists, but history is littered with evidence of such past events where vast lava outpourings originating deep in the Earth accompany the breakup ...

Climate change likely to make Everest even riskier

12 hours ago

Climbing to the roof of the world is becoming less predictable and possibly more dangerous, scientists say, as climate change brings warmer temperatures that may eat through the ice and snow on Mount Everest.

User comments : 5

Adjust slider to filter visible comments by rank

Display comments: newest first

deatopmg
5 / 5 (1) Jul 01, 2009
Did the authors take into consideration that C4 plants were widely distributed in tropical areas 25 mm yrs ago. These can readily prosper at less than 200 ppm CO2 whereas the more common C3 plants can't. Did the authors take this into consideration in their simulations?
PinkElephant
1 / 5 (1) Jul 01, 2009
Possibly the low CO2 levels were a major factor that favored C4 plants in the first place. Otherwise, they're at a disadvantage due to their higher energy requirements.
CWFlink
1 / 5 (1) Jul 01, 2009
"Ultimately, we owe another large debt to plants ... plants have ... stabilized Earth's climate by inhibiting critically low levels of CO2 that would have thrown Earth spinning into space like a frozen ice ball."

So... we owe plants a debt of gratitude for nearly dying of CO2 starvation? Odd choice of words. But that is not all...

I was surprised to find out that 250 - 200 ppm was "near starvation" for plants! The current level of 350 ppm is often compared is 280 ppm in 1850.

...we were NOT far from CO2 "starvation" as recently as 1850!

Consider this quote:
"When CO2 levels become suffocatingly low, plant growth is compromised and the health of forest ecosystems suffer, .... When this happens, plants can no longer help remove CO2 from the atmosphere faster than volcanoes and other sources can supply it."

How rapidly does "weathering" remove CO2?

I had assumed the ONLY natural process to "sequester" CO2 was photosynthesis in green plants. This article implies that weathering is a significant process compared to photosynthesis since the starvation of plants ended weathering, not what I thought would have been more significant: the end of photosynthesis!

This suggests to me that the natural increase in plant life as C02 rises will lead to greater "weathering" and more rapid, natural sequestration of CO2.

How rapidly does this work? Has it been taken into account in models of Global Warming?
CWFlink
1 / 5 (1) Jul 02, 2009
Of course! ...higher CO2 levels -> higher levels of carbolic acid in rain -> greater weathering of stones into carbonates -> reduced CO2

And ...higher CO2 -> greater plant growth -> more cracking of stones and turnover of soil via root action -> more exposure to carbolic acid -> reduced CO2

Thus "photosynthesis" and "weathering" are complementary ways of reducing CO2 levels by virtue of plant growth!

Question: is this symbiotic relationship linear with CO2 levels? ...or exponential? ...or what?

Obsrvation: possibly another unintended consequence of human activity.... when we practice erosion control, we inhibit weathering, and thereby contribute to higher CO2 levels? ...what is the carbon footprint of erosion control?!

Ah... what tangled webs we weave!
out7x
1 / 5 (2) Jul 03, 2009
The earths surface is mostly, 75%, ocean. These simple models say nothing about this.

More news stories

On global warming, settled science and George Brandis

The Australian Attorney General, Senator George Brandis is no stranger to controversy. His statement in parliament that "people do have a right to be bigots" rapidly gained him notoriety, and it isn't hard to understand why ...