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October 1, 2018
Rainforest canopy in Caxiuanã, Brazil.Jake Bryant
Phytotechnicians have observed that when carbon dioxide levels in the atmosphere increase, most plants act in an unusual way: they thicken their leaves.
And as human activity increases the levels of carbon dioxide in the atmosphere, thick-leaved plants seem to be in our future.
But the consequences of this physiological reaction go far beyond the heaviest leaves on many plants. Two scientists at the University of Washington have discovered that thicker-leaved plants can exacerbate the effects of climate change because they would be less effective at sequestering atmospheric carbon, a fact that climate change models to date have not taken into account.
In an article published online Oct. 1 by the journal Global Biogeochemical Cycles, researchers report that, when they incorporated this information into global climate models under the high levels of atmospheric carbon dioxide expected later in the century, was less productive – leaving about 5.8 additional petagrams, or 6.39 million tons of carbon in the atmosphere per year. These levels are similar to the amount of carbon released into the atmosphere each year because of fossil fuel emissions of human origin – 8 petagrams, or 8.8 million tonnes.
"Plants are flexible and respond to different environmental conditions," said Abigail Swann, senior author, assistant professor of biosphere science and atmospheric science at the University of Washington. "But until now, no one has yet tried to quantify the impact of this type of reaction on climate change on the impact of plants on our planet."
Scene near the biological station of the Wayqecha Cloud Forest in Peru's Manú National Park.Abigail Swann
In addition to a weakening of the carbon sink, simulations of Swann and Marlies Kovenock, a PhD student in biology at UW, have shown that global temperatures could increase by 0.3 to 1.4 degrees Celsius change.
"If this unique trait – the thickness of the leaves – in high levels of carbon dioxide has such an important impact on future climate change, we believe that global climate models should take into account Other aspects of plant physiology and behavior the climate will look like later in the century, "said Kovenock, lead author of the paper.
Scientists do not know why plants thicken their leaves as carbon dioxide levels rise in the atmosphere. But the answer has been documented across many types of plant species, such as woody trees; staple crops such as wheat, rice and potatoes; and other plants that undergo C3 carbon fixation, the form of photosynthesis which accounts for about 95% of photosynthetic activity on Earth.
Scene of the boreal forest near Fairbanks, Alaska.Abigail Swann
Leaves can thicken to one-third, altering the surface-to-mass ratio in the leaf and altering plant activities such as photosynthesis, gas exchange, evaporative cooling, and sugar storage. Plants are crucial modulators of their environment – without them, the Earth's atmosphere would not contain the oxygen we breathe – and Kovenock and Swann thought that this thick and predictable response of thickening leaves was an ideal starting point for understanding the physiology of plants will affect the climate of the Earth.
"Plant biologists have collected large amounts of data on the reaction of thickening leaves at high levels of carbon dioxide, including levels of carbon dioxide in the atmosphere that we will see later during the century, "said Kovenock. "We have decided to incorporate known physiological effects of leaf thickening into climate models to determine the effect it would have, if any, on a global scale."
A 2009 article by researchers from Europe and Australia collected and cataloged years of experience on how plant leaves change with different environmental conditions. Kovenock and Swann incorporated the data collected on carbon dioxide reactions into Earth system models that are widely used to model the effect of various factors on global climate patterns.
The concentration of carbon dioxide in the atmosphere is now around 410 parts per million. In a century, it can reach 900 ppm. The carbon dioxide level simulated by Kovenock and Swann with thickened leaves was only 710 ppm. They also found that the effects were worse in some parts of the world. Parts of the Eurasia and Amazon Basin, for example, have shown a minimal increase in temperature. In these areas, thicker leaves can hinder evaporative cooling by plants or cloud formation, Kovenock said.
This map shows the global distribution of additional warming due to thickened leaves – beyond the effect of the rise in atmospheric carbon dioxide at 710 ppm – which was projected in the Kovenock and Swann simulations.Kovenock and Swann, 2018, Global Biogeochemical Cycles
Swann and Kovenock hope that this study shows that it is necessary to take into account the responses of plants to climate change in future climate projections. Researchers could model many other changes in plant physiology and behavior as a result of climate change.
"We now know that even small, seemingly small alterations in plants such as this one can have a global impact on the climate, but we need more data on plant responses to simulate very specific plant change." said Swann. "People are not the only organizations that can influence the climate."
The research was funded by the National Science Foundation and the UW.
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For more information, contact Swann at +1 206-616-0486 or [email protected].
DOI: 10.1029 / 2018GB005883
Grant Numbers: AGS-1321745, AGS-1553715.
Tag (s): Climate Change • College of Arts and Sciences • College of the Environment • Department of Atmospheric Sciences.
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