Meningkatnya
kadar karbon dioksida akan membantu dan menyakiti tanaman
Date:
May 4, 2016
Source:
NASA/Goddard Space
Flight Center
Summary:
konsentrasi karbon dioksida tinggi di atmosfer dapat meningkatkan efisiensi penggunaan air pada tanaman dan jauh mengurangi kehilangan hasil akibat perubahan iklim , menurut sebuah studi baru .
..................
konsentrasi karbon dioksida tinggi di atmosfer
dapat meningkatkan efisiensi penggunaan air pada tanaman dan jauh mengurangi
kehilangan hasil akibat perubahan iklim , menurut sebuah studi NASA baru
.Hasilnya, yang diterbitkan dalam jurnal Nature
Climate Change pada April 18, 2016 menunjukkan beberapa kompensasi untuk dampak
merugikan dari suhu ekstrem dan kelangkaan air yang disebabkan oleh
meningkatnya emisi karbon dioksida dan gas rumah kaca .
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Rising carbon
dioxide levels will help and hurt crops
Date:
May 4, 2016
Source:
NASA/Goddard Space
Flight Center
Summary:
Elevated carbon dioxide concentrations in the atmosphere may increase
water-use efficiency in crops and considerably mitigate yield losses due to
climate change, according to a new study.
..................
Elevated carbon dioxide concentrations in the atmosphere may increase
water-use efficiency in crops and considerably mitigate yield losses due to
climate change, according to a new NASA study.
The results, published in the journal Nature Climate Change on
April 18, 2016 show some compensation for the adverse impacts of temperature
extremes and water scarcity caused by increasing emissions of carbon dioxide
and other greenhouse gases.
Studies have shown that higher concentrations of atmospheric carbon dioxide
affect crops in two important ways: they boost crop yields by increasing the
rate of photosynthesis, which spurs growth, and they reduce the amount of water
crops lose through transpiration. Plants transpire through their leaves, which
contain tiny pores called stomata that open and collect carbon dioxide
molecules for photosynthesis. During that process they release water vapor. As
carbon dioxide concentrations increase, the pores don't open as wide, resulting
in lower levels of transpiration by plants and thus increased water-use
efficiency.
Global climate impact assessments for crops have focused primarily on the impacts
of elevated atmospheric carbon dioxide on yields, said Delphine Deryng, lead
author and a climate scientist at NASA's Goddard Institute for Space Studies
(GISS) in New York City. "There has been very little impact assessment
analysis that looked at the dual effect on yield and water use and how they
play out in different regions of the world, which is critical to anticipating
future agricultural water demands," she said.
To study those effects, for wheat, maize, soybean and rice crops, Deryng
and her co-authors simulated changes in crop yield and evapotranspiration (the
combined transfer of water vapor to the atmosphere due to evaporation and
transpiration) to estimate crop water productivity. Specifically, they looked
at the amount of yield produced per unit of water, which is a common
measurement for assessing crop water-use efficiency.
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Untuk mempelajari efek-efek , gandum , jagung , kedelai dan padi , Deryng dan rekan-rekan penulis men simulasi perubahan hasil panen dan evapotranspirasi ( transfer gabungan uap air ke atmosfer akibat penguapan dan transpirasi ) untuk memperkirakan produktivitas air tanaman . Secara khusus , mereka melihat jumlah hasil panen yang dihasilkan per unit air , yang merupakan pengukuran umum untuk menilai efisiensi penggunaan air oleh tanaman .
The results were synthesized from an ensemble of 30 simulations produced by
six global crop models driven by climate data from five different global
climate models under a "business-as-usual" greenhouse gases emissions
scenario, whereby concentrations of carbon dioxide double by the year 2080
compared with 2000. Two sets of crop experiments were conducted: one which
considered the effects of both atmospheric carbon dioxide concentrations and
their associated climatic changes, and one in which only the associated
climatic conditions were taken into account, which meant keeping carbon dioxide
concentrations at 2000 levels.
Results show that yields for all four crops grown at levels of carbon
dioxide remaining at 2000 levels would experience severe declines in yield due
to higher temperatures and drier conditions. But when grown at doubled carbon
dioxide levels, all four crops fare better due to increased photosynthesis and
crop water productivity, partially offsetting the impacts from those adverse
climate changes. For wheat and soybean crops, in terms of yield the median
negative impacts are fully compensated, and rice crops recoup up to 90 percent
and maize up to 60 percent of their losses.
According to the study, the impact of doubled carbon dioxide concentrations
on crop water productivity and yield varies regionally. Results show that maize
suffers yield losses with doubled carbon dioxide levels, due in large part to
the plant's already greater efficiency at using carbon dioxide for photosynthesis
compared with the other crops. Maize yields fall by 15 percent in areas that
use irrigation and by 8 percent in areas that rely on rain. Even so, losses
would be more severe without the carbon dioxide increase: yields would decrease
21 percent for irrigated maize and 26 percent for rainfed maize.
The larger spread for gains and losses in rainfed maize is attributed
mainly to the drier growing conditions. "The impact on crop water
productivity and yield is strongest in regions like southern Africa where water
is a limiting factor," Deryng said. "Maize in these regions
experience the most relief from better water-use efficiency."
As for wheat, doubled carbon dioxide levels bring about yield increases
across the board.
Rainfed wheat grown at higher latitudes such as those of the United States,
Canada and Europe, which have more moderate temperatures and longer growing
seasons, experience an overall increase in yield of almost 10 percent, while
their consumption of water goes down by a corresponding amount.
For rainfed wheat grown in more arid climates, such as southern Africa and
India, results show that doubled carbon dioxide levels, and their associated
climate change impacts, increase yield by 8 percent, an increase that's driven
by improved crop water productivity of up to 50 percent. As with rainred maize
crops in arid climates, without the carbon dioxide boost these rainfed wheat
crops do not cope as well because of the greater water stress imposed on them,
resulting in a 29 percent reduction in yield.
While these rainfed crops comprise only a small amount of the total wheat
grown worldwide, as with rainfed maize they are often grown in developing
countries that are more vulnerable to swings in production, Deryng said.
"People in these regions depend more on local crop production for
sustenance, so yield fluctuations tend to be more critical for food
security."
The study offers some hope for crops grown in arid, often economically
challenged areas, said Cynthia Rosenzweig, a climatologist at GISS. "For
example, farmers may switch to crops where their improved photosynthesis and
more efficient water use more than offsets losses due to the high temperatures
that climate change will bring."
But Rosenzweig said that more field experiments are needed. "The
uncertainty of carbon dioxide effects are greater in arid regions because
experiments have been carried out mostly in temperate regions of the northern
hemisphere," she said. "We need field observations in these drier
regions in order to validate and further improve our models."
There is also a need for research that explores the impact of elevated
carbon dioxide levels on crop nutrition, which wasn't investigated in this
study. "Crops also need nitrogen to grow, for example, and in many parts
of Africa there's not enough fertilizer," Deryng said. "Imbalances
between nitrogen and carbon in the crop tissues could lead to fewer nutrients
like iron, zinc, along with a reduction in the protein content."
The researchers say their findings cast a light on agriculture globally and
highlight the importance of studying arid and semi-arid cropping systems.
"For farmers, water is essential," Deryng said. "Building on
this research will help them and other stakeholders prepare for production in a
hotter, drier planet."
Story Source:
The above post is reprinted from materials provided byNASA/Goddard
Space Flight Center. Note: Materials may be edited for content
and length.
Journal Reference:
1.
Delphine Deryng, Joshua Elliott, Christian Folberth, Christoph Müller,
Thomas A. M. Pugh, Kenneth J. Boote, Declan Conway, Alex C. Ruane, Dieter Gerten,
James W. Jones, Nikolay Khabarov, Stefan Olin, Sibyll Schaphoff, Erwin Schmid,
Hong Yang, Cynthia Rosenzweig. Regional disparities in the beneficial
effects of rising CO2 concentrations on crop water productivity. Nature
Climate Change, 2016; DOI: 10.1038/nclimate2995
Sumber :