Long-term fate of tropical forests may not be as dire as believed, study says

Long-term fate of tropical forests may not be as dire as believed, says CU Boulder study
A new CU Boulder study indicates tropical forests may surprisingly accelerate their growth in warmer and wetter conditions -- good news because they may take up more CO2 from the atmosphere under such conditions. Credit: University of Colorado

Tropical rainforests are often described as the "lungs of the earth," able to inhale carbon dioxide from the atmosphere and exhale oxygen in return. The faster they grow, the more they mitigate climate change by absorbing CO2.

This role has made them a hot research topic, as scientists question what will happen to this vital sink long-term as temperatures rise and rainfall increases.

Conventional wisdom has held that growth will dramatically slow with high levels of rainfall. But University of Colorado Boulder researchers this month turned that assumption on its head with an unprecedented review of data from 150 forests that concluded just the opposite.

"Our data suggest that as large-scale climate patterns shift in the tropics, and some places get wetter and warmer, forests will accelerate their growth, which is good for taking carbon out of the atmosphere," said Philip Taylor, a research associate with the Institute of Arctic and Alpine Research (INSTAAR). "In some ways, this is a good-news story, because we can expect greater CO2 uptake in tropical regions where rainfall is expected to increase. But there are a lot of caveats."

Ecologists have long thought that forest growth follows a hump-shaped curve when it comes to precipitation: To a point, more rainfall leads to more growth. But after about 8 feet per year, it was assumed too much water can waterlog the ecosystem and slow the growth rate of forests. While working in the Osa Peninsula of Costa Rica, Taylor, who got his doctoral degree in ecology and evolutionary biology at CU Boulder, began to question this assumption.

"Here we were in a place that got 16 feet of rain per year, and it was one of the most productive and carbon-rich forests on Earth. It clearly broke from the traditional line of thinking," he said.

Intrigued, Taylor spent four years synthesizing data on temperature, rainfall, tree growth and soil composition from rainforests in 42 countries, compiling what he believes is the largest pan-tropical database to date.

The study, published April 17 in the journal Ecology Letters, found that cooler forests (below 68 degrees F on average), which make up only about 5 percent of the tropical forest biome, seemed to follow the expected hump-shaped curve. But warmer forests, which are in the majority, did not.

"The old model was formed with a lack of data from warm ," said Taylor. "It turns out that in the big tropical forests that do the vast majority of the 'breathing' the situation is flipped. Instead of water slowing growth down, it accelerates it."

Taylor cautioned this does not mean won't negatively impact tropical forests at all. In the short term, research has shown, droughts in the Amazon Basin have already led to widespread plant death and a 30 percent decrease in carbon accumulation in the past decade.

"A lot of climate change is happening at a pace far quicker than what our study speaks to," he says. "Our study speaks to what we can expect forests to do over hundreds of years."

Because the carbon cycle is complex, with forests also releasing carbon into the atmosphere as plants die, it's still impossible to say what the net impact of a wetter climate might be on the forest's ability to sequester carbon, said senior author Alan Townsend, a professor of environmental studies.

"The implications of the change still need to be worked out, but what we can say is that the forest responds to changes in rainfall quite differently than what has been a common assumption for a long time," said Townsend.

Going forward, the authors hope the findings will set the record straight for educators and scientists.

"Our findings fundamentally change a view of the tropical forest carbon cycle that has been published in textbooks and incorporated into models of future climate change for years," said Taylor. "Given how much these forests matter to the climate, these new relationships need to be a part of future assessments."


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Heavy precipitation speeds carbon exchange in tropics

Journal information: Ecology Letters

Citation: Long-term fate of tropical forests may not be as dire as believed, study says (2017, April 28) retrieved 22 July 2019 from https://phys.org/news/2017-04-long-term-fate-tropical-forests-dire.html
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Apr 29, 2017
Long-term fate of tropical forests may not be as dire as believed,


Of course the "fate" is not as dire as portrayed in the leftist press. 2 million years ago, what is now the Amazon was grassland. At best, rain forests are transitory. As are every other feature on the planet.

Apr 29, 2017
Long-term fate of tropical forests may not be as dire as believed,


Of course the "fate" is not as dire as portrayed in the leftist press. 2 million years ago, what is now the Amazon was grassland. At best, rain forests are transitory. As are every other feature on the planet.

So you don't cure if we just trashed and destroyed the beautiful rain forests just to spite the so called 'lefties'?
I fear there is something very wrong with your sole.

Apr 29, 2017
Long-term fate of tropical forests may not be as dire as believed,


Of course the "fate" is not as dire as portrayed in the leftist press. 2 million years ago, what is now the Amazon was grassland. At best, rain forests are transitory. As are every other feature on the planet.


This is what happens when science is misused for politics. Yes, long-term, in hundreds of thousands or millions of years, the Earth-system MAY re-equilibrate and recover from many injuries. No, that re-equilibration process may be very unpleasant during the short-term represented by human lives and human civilization.

Apr 29, 2017
Industry tells soothing lies to defend its ambitions to profit by environmental damage, Greens tell terrifying lies to oppose industry. Both sides despise reality for not being onside with their narratives, and both sides view the public as dimwitted and gullible (probably 40% true - how else to explain the human world?) Being caught in a lie, though, can be devastating for a position - how much damage was done to the Green cause by Climategate? Our natural world is best defended with truth and clarity, combined with a sharp eye on who is paying for environmental research, an on the reproducibility of results.

Apr 29, 2017
Industry tells soothing lies to defend its ambitions to profit by environmental damage, Greens tell terrifying lies to oppose industry. Both sides despise reality for not being onside with their narratives, and both sides view the public as dimwitted and gullible (probably 40% true - how else to explain the human world?)


Hey look-- someone trying to be fair-minded and objective with regard to the AGW "debate"!

Being caught in a lie, though, can be devastating for a position -


Truth!

how much damage was done to the Green cause by Climategate?


Very little to none, outside of the Rightwing blogosphere.

Our natural world is best defended with truth and clarity, combined with a sharp eye on who is paying for environmental research, an on the reproducibility of results.


Vague wording here makes it difficult to determine the intent of this statement.

Care to offer up a more definitive position?


Apr 29, 2017
Long-term fate of tropical forests may not be as dire as believed,


Of course the "fate" is not as dire as portrayed in the leftist press. 2 million years ago, what is now the Amazon was grassland. At best, rain forests are transitory. As are every other feature on the planet.


The reality 2 million years ago doesn't have any bearing on that of the present in this context, Scrotist.

Tropical rain forest has been the reality for the past 2 million, by your reckoning.

The current interglacial period, which contains all of recorded human history, is expected to last for several thousand more years, and in a very stable temperature regime.

This was all abruptly changed about two hundred years ago, when massive deforestation and fossil fuel burning began with the ramp up of The Industrial Revolution, and into the present. A steady -now accelerating- rise in average temperature is observed.

Do make an effort to keep current, yes?

Apr 29, 2017
That's what they said about coral before 90% of the Great Barrier Reef died in 2 years.

Apr 29, 2017
The problem with climate change in tropical forests isn't just the increased amount of rain in some places. It's that the species that evolved there can't evolve and adapt as quickly as the climate is now changing. They're going extinct already at an unprecedented rate.

Plus this study tells us about increased CO2 uptake in those tropical forests where rainfall increases. But they don't mention the reduced CO2 uptake - and large stored CO2 release from rotting forests not replaced by offspring, and from soils no longer maintained by a viable ecosystem - where drought begins to prevail. It also appears the study doesn't account for changing rainfall patterns across the year, leaving shortages when existing species expect adequate supplies even if overcompensating during seasons the species don't consume it effectively.

In other words it sounds like greenwashing.

Apr 29, 2017
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Apr 30, 2017
The tropical forests could actually profit from global warming if only the greedy "environmentalists" wouldn't propose a "biofuels" for its "solution".

Dingbone

I am not a fan of biofuels but; how can the environmentalists be "greedy" for promoting something they don't personally profit from? That makes no sense.
+ some biofuels can be produced sustainable and without cutting down trees thus can be part of the solution albeit I think generally not the best one unless it is just converting organic waste into biofuel; which is exactly what I think should be done.

(if we neglect, they're the main source of oxygen).

if all the forests were cut down, it would make no noteworthy let alone "dire" difference (less than 0.1%) to the oxygen concentration in the Earth's atmosphere. It would, however, release massive amounts of CO2 that will thus accelerate man made global warming.

Apr 30, 2017
Half of the Earth's biological oxygen budget comes from land, and half from the oceans. It's worth keeping in mind when discussing these things.

Apr 30, 2017
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Apr 30, 2017
Ding Maroon aka Antigoracle sockpuppet YOU don't even qualify to even TRY to bring up costs associated with environmentalist spending, Tell us how Big Filthy Oil has raped every ounce of the earth
reaping trillions upon trillions upon trillions. Now you come try bafoon headedly and bark about the drop in the ocean environmentalists is receiving and spending to protect the earth, against BIG OIL's Relentless profits, whilst destroying the earth, what mental institution will they need to send you to next ?

Apr 30, 2017
how can the environmentalists be "greedy" for promoting something they don't personally profit from
Do you mean "environmentalists" like Rajendra Pachauri? .

Dingbone

NO, I mean all people with genuine concerns about pollution deforestation and the future that are all labelled as "environmentalists" by amoral morons not worth shit because they don't care the less about the future of humanity.

Apr 30, 2017
I can't imagine the mentality required to downvote a statement of obvious fact. Half of our oxygen comes from trees; half comes from oceanic algae. It's just a simple fact. If you don't like it, go argue with the Earth. Good luck with that. Meanwhile, get over it. Dumb da dumb dumb. Dumb da dumb dumb duhhh.

May 01, 2017
I can't imagine the mentality required to downvote a statement of obvious fact. Half of our oxygen comes from trees; half comes from oceanic algae.

Da Schneib

Nobody here including me denied nor disbelieves that much (not all) of the oxygen in the Eath's atmosphere originally came from plants/cyanobacteria.
However, If you just do the maths with the basic scientifically proven chemistry and physics equations and determine how much oxygen will be actually lost from the atmosphere if all the forests were cut and burned/rotted, the figure you will get is less than 0.1% of the total amount of oxygen in the Earth's atmosphere will be lost via convection into CO2 by the chemical addition of carbon and then that figure will stabilize i.e. there would be no further lose of oxygen. That isn't a reduction in oxygen sufficient to harm Earth's life. So it isn't the oxygen levels we should be concerned about but the extra greenhouse effect of the CO2 if we lost all the forests

May 01, 2017
misprint;
The above

"...oxygen in the Earth's atmosphere will be lost via convection into CO2 by ..."

should have been;

"...oxygen in the Earth's atmosphere will be lost via chemical conversion into CO2 by ..."

May 02, 2017
Caliban "Vague wording here makes it difficult to determine the intent of this statement.

Care to offer up a more definitive position?"

To clarify - without accurate data and a realistic understanding of the environment we can't expect to find or set effective boundaries for sustainable activity. Can we harvest 1% of a forest annually, or 5%, without major changes? What portion of a fish population can be caught yearly without a collapse? What is the real environmental footprint per kilowatt hour of natural gas or corn ethanol or wind turbines? I understand that it's all a vast and highly complex subject, often without definitive answers, but I don't think lies can help us arrive at real sustainability.

May 02, 2017
@humy your typo noted and I will correct inline to preserve your intended meaning.

I can't imagine the mentality required to downvote a statement of obvious fact. Half of our oxygen comes from trees; half comes from oceanic algae.
Da Schneib
Nobody here including me denied nor disbelieves that much (not all) of the oxygen in the Eath's atmosphere originally came from plants/cyanobacteria.
It's a very important point here to note that most of the oxygen in the atmosphere has been generated in historical times, not geological times. The amount of oxygen generated by the biosphere is enormous; so is the amount consumed.

It's completely ignoring the oxygen cycle to claim that the Earth's oxygen was created billions of years ago by cyanobacteria. Oxygen creation and oxygen consumption have proceeded creating turnover for those billions of years, and practically none of the oxygen currently in the atmosphere was created billions of years ago.

[contd]

May 02, 2017
[contd]
If we significantly compromise either oceanic or land-based oxygen production, the results will be far worse than global warming. Screw either one up and you better be able to survive permanently at oxygen levels equivalent to current 10,000 foot levels; and if you have ever been at 10,000 feet, this should scare the crap out of you. This isn't little games with CO2 levels; this is the air you have to be able to breathe to live. I been there and when I came back I barfed for two days. I did, however, see Omega Centauri, so I consider it worthwhile.

Ocean acidification is by far the most frightening effect of CO2 increase. Global warming is an afterthought and of minor importance. Scientists have been pointing this out now for decades and no one is listening.

May 02, 2017
[contd]
However, If you just do the maths with the basic scientifically proven chemistry and physics equations and determine how much oxygen will be actually lost from the atmosphere if all the forests were cut and burned/rotted, the figure you will get is less than 0.1% of the total amount of oxygen in the Earth's atmosphere will be lost via convection into CO2 by the chemical addition of carbon and then that figure will stabilize i.e. there would be no further lose of oxygen. That isn't a reduction in oxygen sufficient to harm Earth's life. So it isn't the oxygen levels we should be concerned about but the extra greenhouse effect of the CO2 if we lost all the forests
That's 0.1% per year. We really don't want to multiply that out to 1,000 years and lose 10% of the oxygen in our atmosphere.

May 03, 2017
Caliban "Vague wording here makes it difficult to determine the intent of this statement.

Care to offer up a more definitive position?"

To clarify - without accurate data and a realistic understanding of the environment we can't expect to find or set effective boundaries for sustainable activity. Can we harvest 1% of a forest annually, or 5%, without major changes? What portion of a fish population can be caught yearly without a collapse? What is the real environmental footprint per kilowatt hour of natural gas or corn ethanol or wind turbines? I understand that it's all a vast and highly complex subject, often without definitive answers, but I don't think lies can help us arrive at real sustainability.


Right.
That pretty much settles you as a Deniersphere inhabitant, posing as a "skeptic".

Your "questions" are bogus, reasoning nonexistent, and your purposeful ignorance of the science is just that.

Thus my question to you in the first place.

May 03, 2017
It has come to my attention while re-reading this thread that I did not post a source for my claim that the distribution of oxygen production is about 50/50 land and sea. Here is a pretty recent, well-sourced article on it: https://ic.ucsc.e...ycle.pdf

Note that on page 521, the paper gives production figures that are quite close to my estimate. They differ by less than 10%.

May 04, 2017
Caliban

All those questions are variants on "what are the ecological limits to economic growth?" How is that a bogus question? How do that "deny" anything? Should we deny that limits exist, and grow ourselves into a Malthusian collapse? If we have passed a limit in any area (such as co2 emissions, where we certainly have) should we not want to know the most effective and least damaging technologies for our move back to a sustainable position?

May 04, 2017
Caliban

All those questions are variants on "what are the ecological limits to economic growth?" How is that a bogus question? How do that "deny" anything?[...] most effective and least damaging technologies for our move back to a sustainable position?


A long way from the above to your earlier comment:

To clarify - without accurate data and a realistic understanding of the environment we can't expect to find or set effective boundaries for sustainable activity.


There is no dearth of data or understanding. Certainly there are details not yet included, and some small margin of uncertainty, but the big picture is clear, and there is no time left for nitpicking or fence sitting, which you are clearly calling for with such statements.

I would recommend that you dispense with the pussyfooting, and say clearly and unequivocally what you mean, and thereby avoid criticism for a stance that you may --or may not-- be taking.

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