Study says Earth can sustain more terrestrial plant growth than previously thought

Aug 26, 2014
Scientists have historically underestimated the potential productivity of the earth's land plants, researchers report in a new study. Credit: NASA Earth Observatory image by Jesse Allen

A new analysis suggests the planet can produce much more land-plant biomass – the total material in leaves, stems, roots, fruits, grains and other terrestrial plant parts – than previously thought.

The study, reported in Environmental Science and Technology, recalculates the of terrestrial , and finds that it is much higher than many current estimates allow.

"When you try to estimate something over the whole planet, you have to make some simplifying assumptions," said University of Illinois plant biology professor Evan DeLucia, who led the new analysis. "And most previous research assumes that the maximum productivity you could get out of a landscape is what the natural ecosystem would have produced. But it turns out that in nature very few plants have evolved to maximize their growth rates."

DeLucia directs the Institute for Sustainability, Energy, and Environment at the U. of I. He also is an affiliate of the Energy Biosciences Institute, which funded the research through the Institute for Genomic Biology at Illinois.

Estimates derived from satellite images of vegetation and modeling suggest that about 54 gigatons of carbon is converted into terrestrial plant each year, the researchers report.

"This value has remained stable for the past several decades, leading to the conclusion that it represents a planetary boundary – an upper limit on global biomass production," the researchers wrote.

But these assumptions don't take into consideration human efforts to boost plant productivity through genetic manipulation, plant breeding and land management, DeLucia said. Such efforts have already yielded some extremely productive plants.

For example, in Illinois a hybrid grass, Miscanthus x giganteus, without fertilizer or irrigation produced 10 to 16 tons of above-ground biomass per acre, more than double the productivity of native prairie vegetation or corn. And genetically modified no-till corn is more than five times as productive – in terms of total biomass generated per acre – as restored prairie in Wisconsin.

Some non-native species also outcompete native species; this is what makes many of them invasive, DeLucia said. In Iceland, for example, an introduced species, the nootka lupine, produces four times as much biomass as the native boreal dwarf birch species it displaces. And in India bamboo plantations produce about 40 percent more biomass than dry, deciduous tropical forests.

Some of these plants would not be desirable additions to native or managed ecosystems, DeLucia said, but they represent the untapped potential productivity of plants in general.

"We're saying this is what's possible," he said.

The team used a model of light-use efficiency and the theoretical maximum efficiency with which plant canopies convert solar radiation to biomass to estimate the theoretical limit of net primary production (NPP) on a global scale. This newly calculated limit was "roughly two orders of magnitude higher than the productivity of most current managed or natural ecosystems," the authors wrote.

"We're not saying that this is even approachable, but the theory tells us that what is possible on the planet is much, much higher than what current estimates are," DeLucia said.

Taking into account global water limitations reduced this theoretical limit by more than 20 percent in all parts of the terrestrial landscape except the tropics, DeLucia said. "But even that water-limited NPP is many times higher than we see in our current agricultural systems."

DeLucia cautions that scientists and agronomists have a long way to go to boost plant productivity beyond current limits, and the new analysis does not suggest that shortages of food or other plant-based resources will cease to be a problem.

"I don't want to be the guy that says science is going to save the planet and we shouldn't worry about the environmental consequences of agriculture, we shouldn't worry about runaway population growth," he said. "All I'm saying is that we're underestimating the productive capacity of plants in managed ecosystems."

Explore further: Size and age of plants impact their productivity more than climate, study shows

More information: The paper, "The theoretical limit to plant productivity," is available online: pubs.acs.org/doi/abs/10.1021/es502348e

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ryggesogn2
1.7 / 5 (11) Aug 26, 2014
"I don't want to be the guy that says science is going to save the planet and we shouldn't worry about the environmental consequences of agriculture, we shouldn't worry about runaway population growth,"

Why not?
Will you get kicked out of the 'Club-for-anti-growth'?
freeiam
1.8 / 5 (10) Aug 26, 2014
So, orders of a magnitude increased CO2 capture.
It's a bad year for the climate whiners.
Modernmystic
1.7 / 5 (6) Aug 26, 2014
"I don't want to be the guy that says science is going to save the planet and we shouldn't worry about the environmental consequences of agriculture, we shouldn't worry about runaway population growth


Good GOD no you don't! That's too close to the objective truth, you'd be ignoring the values and worldviews of millions that don't agree with reality.

So, orders of a magnitude increased CO2 capture.
It's a bad year for the climate whiners.


How would it be bad news? It would actually be good news for us all. Too bad we can't actually do it.
orti
1.4 / 5 (9) Aug 26, 2014
There is a theory that the planet has been CO2 starved relative to ancient levels. This may be supporting evidence. That half of man's CO2 output is being immediately absorbed by something is another.
antialias_physorg
4.6 / 5 (10) Aug 26, 2014
So, orders of a magnitude increased CO2 capture.
It's a bad year for the climate whiners.

Not sustainably, though. Plants need a bit more than just CO2 from the air.

And in any case - you're missing the point again. Plants are a buffer system at best (as their decay/use releases as much CO2 as they grabbed in the first place). Buffer systems do not make problems go away.
ryggesogn2
1.4 / 5 (10) Aug 26, 2014
Plants are a buffer system at best

Plants are food.
Jayded
1.4 / 5 (10) Aug 26, 2014
What a stupid study. How the heavens these people manage to get funding for such stupid studies is just beyond me. As far as I remember there was a period in Earths history we refer to a the carboniferous period (late Devonian - early Permian) and yup the planet could and did support more plant bio mass and yup, probably more than we originally expected.
TheGhostofOtto1923
4 / 5 (4) Aug 26, 2014
What, more kudzu and giant hogweed? No thanks.
antialias_physorg
4.5 / 5 (8) Aug 26, 2014
Plants are food.

So what do you think happens to them when eaten? In the end the carbon gets released again by the animal that ate it (either as CO2 when breathing out, as methane after the digestion process, or eventually during the process of that animal being turned into bacteria-food - which is the most microscopic fraction. The vast, vast majority is released through the first two processes)
runrig
4.6 / 5 (9) Aug 26, 2014
What a stupid study. How the heavens these people manage to get funding for such stupid studies is just beyond me. As far as I remember there was a period in Earths history we refer to a the carboniferous period (late Devonian - early Permian) and yup the planet could and did support more plant bio mass and yup, probably more than we originally expected.


Twas a totally different planet my friend and in no way analogous.
thingumbobesquire
4 / 5 (2) Aug 27, 2014
Bravo. I applaud this unexpected optimism. Human improved nature is the hallmark of the concept of the noösphere. http://larouchepu...oos.html
drodsaxman
3 / 5 (2) Aug 27, 2014
Good to see potential to increase biomass alternative energy use vs carbon based fuel such as oil and gas. Another grass they call them C4 feedstock to consider and research more is Giant King Grass even greater yield per acre the giaganteus micanthus. Both are preferred over carbons. Thanks
drodsaxman
ryggesogn2
1.7 / 5 (6) Aug 27, 2014
Plants are food.

So what do you think happens to them when eaten? In the end the carbon gets released again by the animal that ate it (either as CO2 when breathing out, as methane after the digestion process, or eventually during the process of that animal being turned into bacteria-food - which is the most microscopic fraction. The vast, vast majority is released through the first two processes)

Let's kill all plants. That will save the planet.

What makes quality soil black? Carbon.
Compost ingredients:
shredded newspaper* 170:1
straw 75:1
shredded cardboard 350:1
dried leaves 70:1
old hay 55:1
sawdust 400:1
wood chips 400:1
small branches/twigs 500:1
paper towel 110:1
tissue paper 70:1
wood ashes 25:1
dried grass clippings 50:1
pine needles** 80:1
Everyone is plant based.
http://www.compos...nts.html
AGWites whine about extracting carbon. That's what plants DO. Turn water, CO2 and O2 into plants made of carbon.
ViperSRT3g
4.3 / 5 (6) Aug 27, 2014
Plants are food.

So what do you think happens to them when eaten? In the end the carbon gets released again by the animal that ate it (either as CO2 when breathing out, as methane after the digestion process, or eventually during the process of that animal being turned into bacteria-food - which is the most microscopic fraction. The vast, vast majority is released through the first two processes)

Let's kill all plants. That will save the planet.

What makes quality soil black? Carbon.
Compost ingredients:
shredded newspaper* 170:1
straw 75:1
shredded cardboard 350:1
dried leaves 70:1
old hay 55:1
sawdust 400:1
wood chips 400:1
small branches/twigs 500:1
paper towel 110:1
tissue paper 70:1
wood ashes 25:1
dried grass clippings 50:1
pine needles** 80:1
Everyone is plant based.
http://www.compos...nts.html
AGWites whine about extracting carbon. That's what plants DO. Turn water, CO2 and O2 into plants made of carbon.

And your point is?
antialias_physorg
4.2 / 5 (5) Aug 27, 2014
That's what plants DO. Turn water, CO2 and O2 into plants made of carbon.

...an plants in turn get turned into? C'mon...you're so close to using your brain.
ryggesogn2
1.7 / 5 (6) Aug 27, 2014
That's what plants DO. Turn water, CO2 and O2 into plants made of carbon.

...an plants in turn get turned into? C'mon...you're so close to using your brain.

Soil.
ryggesogn2
1.8 / 5 (5) Aug 27, 2014
We plant corn for silage to feed our dairy cows over the winter.
After the first frost the corn is chopped, put into a silo, fermented and fed to cows.
Cows extract nutrients and expel the rest which is collected and spread back onto the field to enrich the soil.
The straw leftover from small grains like oats and wheat are used for bedding or chopped an left in the field, plowed under to enrich the soil.
Many rice growers burn the straw leaving carbon ash in the fields.
antialias_physorg
4.2 / 5 (5) Aug 27, 2014
Soil.

Earlier you said food.

Hint: if we want to use plants to sequester CO2 we'll be doing what Earth did over billions of years: create coal deposits, oil deposits or peat deposits. Note the 'billions of years'. This is not something that happens in a few years to any appreciable scale.

Instead we are actively digging up these deposits and burning them. Now it takes a very special kind of idiot to not see a problem with this (and I grant you: you are very special in this case)

Cows extract nutrients and expel the rest which is collected and spread back onto the field to enrich the soil.

Are you aware of this mechanism called breathing? O2 in, CO2 out. It's simple. Try it some time. Your brain might start working if it gets some O2.

inany case - even the part we put back on the fields is just in a cycle. It doesn't sequester diddly squat. It's just a buffer system. And buffer systems are not a solution to a compounding addition of CO2.
Modernmystic
3 / 5 (2) Aug 27, 2014
What' you're saying is correct, anti, but if you increase the effective pool of biomass by two orders of magnitude you effectively instantly increase the sequestration potential by as much...because after all when they're plants and they're considered living "biomass" they've got that carbon locked up pretty tight....

It' is a buffer, and it's not a "solution" I agree, but there are reasons to have bigger buffers in all kinds of things. A buffer THAT big could actually effectively sequester all the carbon we've put into the air thus far. The question is what happens when we fill THAT huge a buffer...not good...
antialias_physorg
4 / 5 (4) Aug 27, 2014
two orders of magnitude you effectively instantly increase the sequestration potential by as much

Two orders is the theoretical upper limit. Nowhere near a practically realizable goal. The limit on biological matter is the LEAST available resource - and CO2 ain't that. (It's water. Many agricultural regions are already at the sustainable water limit or well beyond.)

The catastrophe will then be much worse because in the meantime you've not reacted to the problem because it looked like nothing was happening.

A buffer THAT big could actually effectively sequester all the carbon

A buffer is not sequester. Not one gram of carbon gets sequestered that way.
ryggesogn2
1.8 / 5 (5) Aug 27, 2014
Earlier you said food.

First food, then soil.
even the part we put back on the fields is just in a cycle

It's not a cycle. It's additive. You just said so. Peat bog, pararie sod, ...
Plants take CO2, O2 and water, and a few minerals from the soil, and create plant stuff: sugars, cellulose, etc.
When it dies, the plant stuff is added to the soil.
Modernmystic
2 / 5 (4) Aug 27, 2014

A buffer is not sequester. Not one gram of carbon gets sequestered that way.


So then the carbon in one tree is the same as the carbon in a hundred? You'll have to explain that one.

It isn't sequestered in the sense that it's buried and turning into hydrocarbons...but it IS out of the system and in the buffer.
NOM
3 / 5 (2) Aug 27, 2014
That's what plants DO. Turn water, CO2 and O2 into plants made of carbon.
...an plants in turn get turned into? C'mon...you're so close to using your brain.

He failed.
antialias_physorg
3.7 / 5 (3) Aug 28, 2014
So then the carbon in one tree is the same as the carbon in a hundred? You'll have to explain that one.

You're just shifting the CO2 in the air down the road (till the next forrest fire, or any other condition in which you cannot sustain this above-normal vegetation...e.g. when we run out of fertilizer or groundwater). Then it hits you all at once and hard. And then you will not be given time to react. Change will be swift.

A buffer is not a sequester. A sequester takes the carbon out of the system permanently (with no chance of re-release). A sequester is also (for all intents and purposes) infinite. A buffer is finite and leaves you where you started from after some time (as well as demanding continual investment to keep it going in this case).