[MCN] U of Montana researchers on CO2 fertilization, forest, farm

[Lance Olsen]

THE UNIVERSITY OF MONTANA PUBLIC RELEASE: 9-DEC-2015
UM study: Plants absorb less carbon dioxide than models show
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Running said the study could help researchers 
understand how Montana forests and crops will 
respond to the changing climate.

"While increasing CO2 does aid photosynthesis, 
the changing climate is reducing growing season 
water supplies," he said.
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While global plant growth has increased slightly 
during the past 30 years, researchers at the 
University of Montana found it hasn't increased 
as much as some scientists predicted.

Former UM doctoral student Bill Smith and current 
UM Professors Cory Cleveland, Ashley Ballantyne 
and Steve Running studied the relationship 
between atmospheric carbon dioxide from human 
emissions and a corresponding growth in plant 
life, and they compared their results with 
existing models. The study was published this 
month in the journal Nature Climate Change. 
Abstract of article is available free online at
http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2879.htm

Carbon dioxide enhances plant growth, and plants 
absorb atmospheric carbon dioxide. Smith and the 
study co-authors compared measurements of plant 
productivity estimated by models with those 
measured by satellites. They concluded that 
current models unrealistically overpredict the 
ability of plants to offset growing greenhouse 
gas emissions, suggesting that the earth's 
capacity to take up future carbon dioxide 
emissions may be less than previously thought.

"Current earth-system models assume that global 
plant growth will provide the tremendous benefit 
of offsetting a significant portion of humanity's 
CO2 emissions, thus buying us much-needed time to 
curb emissions," Smith said. "Unfortunately, our 
observation-based estimates of global vegetation 
growth indicate that plant growth may not buy us 
as much time as expected, [so] action to curb 
emissions is all the more urgent."

The authors identify two important factors that 
could drive the divergence between 
satellite-based results and model-based results: 
availability of water and availability of 
nutrients. Satellite data indicate warmer climate 
conditions resulting from rising atmospheric 
carbon dioxide may increase stress in plant 
water, counteracting any positive effect of 
carbon dioxide. Additionally, limited 
availability of nitrogen and phosphorus in the 
environment also could limit the ability of 
plants to soak up additional carbon dioxide.

These findings indicate that current climate 
models do not accurately predict future plant 
growth and suggest that allowable emissions 
targets based on these models may need 
re-evaluation. The authors recommend better 
integration among model, satellite and 
on-the-ground measurement approaches to improve 
our understanding of the effects of rising 
atmospheric carbon dioxide on plant growth

The work provides an important step toward 
understanding how plants may respond (or not 
respond) to rising atmospheric carbon dioxide, as 
well as highlights ways scientists from different 
specialties can work together to reach a deeper 
understanding of how ecosystems will respond to 
global change, says Sasha Reed, a U.S. Geological 
Survey scientist and a co-author of the paper.

"We have many scientific tools in our toolbox," 
Reed said, "and bringing them together is a 
powerful approach to asking questions and to 
solving problems."

Running said the study could help researchers 
understand how Montana forests and crops will 
respond to the changing climate.

"While increasing CO2 does aid photosynthesis, 
the changing climate is reducing growing season 
water supplies," he said. "The result will help 
form policies for forest, range and water 
management."

Running suggests that satellite-derived 
measurements might, for now, be a more accurate 
way to measure how carbon dioxide fertilization 
impacts global terrestrial ecosystems.
###
Abstract of article is available free online at 
http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2879.html.


-- 
==================================================================
"The most painful and expensive way to deal with 
global climate change will be to ignore it until 
something happens that elicits powerful public 
demands for immediate and Draconian action."

Jonathan Lash. 
"As the earth heats up. " 
Journal of Commerce  August 16, 1996.
=============================================================================
"Š the race between climate dynamics and  climate 
policy will be a close one Š." and " Š requires 
an industrial revolution for sustainability 
starting now." 

Hans Joachim Schellenhuber.
Global warming: Stop worrying, start panicking?
Proceedings of the National Academy of Sciences 
September 23, 2008  vol. 105  no. 38
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