The Amazon and global warming

[lemit]

I recently heard a theory that intrigues me:

 

The Amazon basin was populated by millions in highly developed cultures and technologies until the end of the Fifteenth Century, in other words, during the Medieval Warm Period.

 

When the native cultures died and the forests reclaimed the Amazon, we entered the Little Ice Age.

 

Now, accelerated destruction of the Amazon forests and the acceleration of global warming seem to coincide.

 

That's the logic. Can anybody tell me what the science says?

 

Thanks.

 

--lemit

[lemit]

Also, I have long considered the Amazon to be the third pole or the fifth ocean in its influence on climate. That's why I was thrilled to hear this theory.

 

Are there other areas that might compete for the designation of third pole? Fifth ocean? I know about the Antarctic. For this discussion, it's a redundancy.

 

--lemit

[Moontanman]

I'm not sure about a third pole but check out this link for the connection with the plague.

 

Way of the Woo: The Pandemic vs. The Maunder Minimum

[Essay]

Very cool idea! Well, I should say a hot idea and a cool link! Thanks MTM!!!

 

While I like the implications of the article, it places the LIA from 1250-1650. I thought the LIA was more like wiki says: "Some confine the Little Ice Age to approximately the 16th century to the mid 19th century. It is generally agreed that there were three minima, beginning about 1650, about 1770, and 1850, each separated by slight warming intervals."

 

Implications: Massive collapses of local civilizations due to population collapses, from the 1350's to the 1650's may have led to a large drawdown of CO2 as jungles, forests and animal herds burgeoned--and nobody remained to manage the herds, burn off the underbrush and litter, and clear/cultivate the lands. This applies to all of the Americas (and Europe), but maybe Africa and Asia too.

 

I thought the MWP was from 800-1500. This would coincide with when the lands were being intensively managed--20 million Incas, Cahokia, etc.--releasing CO2.

 

Well, I was close: wiki says, "The Medieval Warm Period was a time of warm weather around AD 800-1300 during the European Medieval period."

 

p.s. wiki says: "Cahokia is the site of an ancient Native American city (650-1400 CE) near Collinsville, Illinois in the American Bottom floodplain, across the Mississippi River from St. Louis, Missouri. The 2,200-acre (8.9 km2) site includes at least 109 man-made earthen mounds. Cahokia Mounds is the largest archaeological site related to the Mississippian culture, which developed advanced societies in eastern North America centuries before the arrival of Europeans."

 

p.p.s. I did not know this, but wiki also says: "The plague resurfaced in the mid-18th century; like the Black Death, the Third Pandemic began in Central Asia. It spread worldwide, killing millions, into the early 20th century."

[lemit]

Now I'm confused. I'd always heard that the Little Ice Age started in the Fifteenth Century and finally disappeared in the late Nineteenth Century. I think that has been demonstrated.

 

So, what about the importance of the Amazon to the world's climate? That's still the essential question.

 

--lemit

[Essay]

So, does that mean the Amazon isn't as important to the earth's climate as I thought it was or just that the specific theory is questionable, or neither?

 

I think it lends support to the idea that humans have been affecting the climate for over a millinneum; we're just affecting it much more in the 20th century and now.

[Essay]

Now, another contender has entered the arena, vying for its place in history as the cause of the Little Ice Age: the pandemic. Richard Nevle and Dennis Bird of Stanford have examined sediment cores and soil samples dating back 5000 years and noted a precipitous drop in charcoal ash following periods of major pandemics. This indicated a massive decrease in the clearing of forests by burning to create more land for crops. While the population recovered (remember, Europe lost 20-30 million people in the span of six years), abandoned land began to regrow. Whole new forests sprouted, sucking CO2 out of the atmosphere, effectively removing layers from the Earth's thermal blanket. Moreover, their data aligns nearly perfectly (or so they say) with other information (heavy/light carbon isotope ratios) detailing the drop in atmospheric CO2 at the same time.

This (above) is the point that I thought was supporting.

 

I think the dates for LIA in that link are way off, though.

But with the correct dates, it supports the idea even more--though I'm not sure "how" their data lines up with "which" dates....

...or words to that effect.

[engineerdude]

Don't the world's oceans, which cover 70% of our planet, soak up the vast majority of planetary CO2? There's many articles that discuss this, but here's one:

 

Carbon dioxide: where does it all go? | Science News | Find Articles at BNET

 

Don't get me wrong I think the Amazon is cool and all, but as far as being a CO2 sink it isn't very significant.

[Essay]

I think the oceans and lands are about equivalent in CO2 cycling abilities; with most of the oceans being a "desert" for life--coastal waters being the main productive areas.

 

...and the oceans remained mostly as a constant in equation of CO2 balance--until the industrial age. I was focusing on the land-based contribution to CO2 balance as the factor being strongly influenced by civilization; with the Amazon being a prime example.

Being the fastest growing forests, they may have drawn down the most CO2 after the American civilizations collapsed.

 

It's something like 100 billion tons of carbon dioxide exchanged by the lands each year. If globally, or even regionally at various times through history, we shifted that balance by just 2-3 billion tons/year, then climate could be influenced over the course of decades or longer--assuming CO2 does act as a fine-tuning thermostat. After a large collapse the shift could be 5-10 billion tons/year, for decades or even a century or longer.

 

The point of this thread seems to be that globally there was a large collapse in many civilizations around 1500--the transition between the MWP & LIA--especially the intensively agrarian New World civilizations that seem to have cultivated two continents.

[engineerdude]

I think the oceans and lands are about equivalent in CO2 cycling abilities; with most of the oceans being a "desert" for life--coastal waters being the main productive areas.

 

...and the oceans remained mostly as a constant in equation of CO2 balance--until the industrial age. I was focusing on the land-based contribution to CO2 balance as the factor being strongly influenced by civilization; with the Amazon being a prime example.

Being the fastest growing forests, they may have drawn down the most CO2 after the American civilizations collapsed.

 

It's something like 100 billion tons of carbon dioxide exchanged by the lands each year. If globally, or even regionally at various times through history, we shifted that balance by just 2-3 billion tons/year, then climate could be influenced over the course of decades or longer--assuming CO2 does act as a fine-tuning thermostat. After a large collapse the shift could be 5-10 billion tons/year, for decades or even a century or longer.

 

The point of this thread seems to be that globally there was a large collapse in many civilizations around 1500--the transition between the MWP & LIA--especially the intensively agrarian New World civilizations that seem to have cultivated two continents.

 

I find this collapse of civilizations around 1500 intriguing as well - but I seriously doubt it has anything to do with CO2. Perhaps there is something that both causes large-scale disruptions and also causes a change in CO2 levels, but I do not see how the Amazon can have anything to do with it, at least not directly.

 

To explain, look at this:

 

total biomass of all land plants: 1.25 billion tons

total biomass of blue-green algae in oceans: 44 billion tons

 

Far from being a "desert" of life, the oceans contain 97.2% of all the plant life on our planet, by mass.

 

The blue-green algae (cyanobacteria) are what gave us our current atmosphere starting 2.8 billion years ago, and they continue, through sheer volume, to say what happens in our air.

 

Here's a nice article on cyanobacteria:

 

Cyanobacteria - Wikipedia, the free encyclopedia

[Essay]

Originally Posted by Essay

I think the oceans and lands are about equivalent in CO2 cycling abilities; with most of the oceans being a "desert" for life--coastal waters being the main productive areas.

 

...and the oceans remained mostly as a constant in equation of CO2 balance--until the industrial age. I was focusing on the land-based contribution to CO2 balance as the factor being strongly influenced by civilization; with the Amazon being a prime example.

Being the fastest growing forests, they may have drawn down the most CO2 after the American civilizations collapsed.

 

It's something like 100 billion tons of carbon dioxide exchanged by the lands each year. If globally, or even regionally at various times through history, we shifted that balance by just 2-3 billion tons/year, then climate could be influenced over the course of decades or longer--assuming CO2 does act as a fine-tuning thermostat. After a large collapse the shift could be 5-10 billion tons/year, for decades or even a century or longer.

 

The point of this thread seems to be that globally there was a large collapse in many civilizations around 1500--the transition between the MWP & LIA--especially the intensively agrarian New World civilizations that seem to have cultivated two continents.

 

I find this collapse of civilizations around 1500 intriguing as well - but I seriously doubt it has anything to do with CO2. Perhaps there is something that both causes large-scale disruptions and also causes a change in CO2 levels, but I do not see how the Amazon can have anything to do with it, at least not directly.

 

To explain, look at this:

 

total biomass of all land plants: 1.25 billion tons

total biomass of blue-green algae in oceans: 44 billion tons

 

Far from being a "desert" of life, the oceans contain 97.2% of all the plant life on our planet, by mass. I said "most" of the oceans are deserted, but your percentage must still be wrong (uncitable?).

 

The blue-green algae (cyanobacteria) are what gave us our current atmosphere starting 2.8 billion years ago, and they continue, through sheer volume, to say what happens in our air.

 

 

Well, yes; those numbers sound about right--as far as I know--but you need to include "the rest of the story" as Paul Harvey used to say.

 

For the oceans there are also the higher life forms, fish and mammals--comprising a billion tons or so--that grow on that 44 billion tons of plankton.

Total fish biomass in worlds oceans estimated to be 2 billion tonnes

===

 

Similarly on land, there are those "1.25 billion tons [of] land plants" that you mention, which are supported by the terrestrial microbiome.

 

Over 1500 billion tons of biomass fills our terrestrial biome--in our soils. So compared to your 44 gigatons of plankton, I think our soils are more significant (do you still think it's 97% in the oceans?).

http://picea.sel.uaf.edu/manuscripts/mcguirehobbierep97.pdf

For contemporary climate and an atmospheric C02 concentration of 312.5 ppmv, TEM [Terrestrial Ecosystem Model] estimates global carbon storage of 1781.4 x 10^15 gC (Pg C). This estimate does not include the carbon content of inert soil organic matter.

It is our agricultural practices, cultivation and harvesting regimes, and land use/land cover changes which affect the largest carbon pool.

 

I agree that the microbes control our atmosphere, but that is my point--just look what we've done to the soils of this planet through the process of civilization--desertification, deforestation, and denitrification.

 

~ :lol:

 

p.s. (1 PgC = 1 GtC) one petagram = one gigaton (billion tons)

[engineerdude]

Essay,

 

I do not agree that soil microbes have much to do with the composition of our atmosphere. The green plants that live by photosynthesis are what removes CO2 from the air - the rest of the life forms on our planet do the very opposite. And, as I have posted above, 97.2% of the plant life that scrubs the CO2 lives in the oceans. Desertification, intense farming, etc. all are unpleasant, but there just aren't enough land plants to affect CO2 levels much.

[Essay]

...photosynthesis...removes CO2 from the air -- the rest of the life forms on our planet do the very opposite.

This is a common, complicated misunderstanding.

 

Your focus on plants (over biomass) is understandable since we're talking about CO2 and we all know that plants take up CO2.

 

Biomass is more important because, to create biomass, CO2 must be converted into living creatures.

 

To oversimplify it [...and not counting the chemophiles.]--

CO2 + light = sugar

sugar + plants = plant biomass

plant biomass + animals = more animals + (less exhaled CO2 than was in the original plant biomass).

 

Animals (and microbes) are sequestered CO2.

This is true in the same way that trees, plants, and algae are sequestered CO2.

 

A food chain is just a subjective way of viewing a carbon sequestration chain.

Similar to the way that top predators accumulate toxins, top predators are accumulated (sequestered) CO2.

Whether it's 100 pounds of meat, or 100 pounds of bacteria, or 100 pounds of tree; they each take about 100 pounds of CO2 to produce. Meat is sequestered carbon. Life propagates sequestered carbon.

===

 

...put another way....

Ultimately all biomass comes from CO2 (or CH4, methane).

Photosynthesis "fixes" carbon, it doesn't create biomass.

Y'know, plants breath oxygen to grow and build tissue (biomass) just like animals and microbes do.

 

Photosynthesis is just a "food" (energy) accumulation mechanism. Plants, like animals and microbes, create more biomass by metabolising "food" using oxygen--burning the food and exhaling CO2.

Don't make the mistake of thinking photosynthesis creates biomass; it only creates food--so that life can burn that food (using oxygen) to create more biomass. The point is that some of the "fixed" CO2 becomes biomass--tissues, cell membranes/walls, and inter/intracellular matrices or fluids--not all of the CO2 is exhaled.

 

Shifting the balance between photosynthesis and respiration will have some effect on that "100 billion tons of carbon dioxide exchanged" each year, but it is the net increase or decrease in that 1,500 billion tons of biomass that will, "through sheer volume," most strongly affect our atmosphere.

...and of course, our emissions become a problem if there is not an offsetting increase in biomass--to sequester the emissions--say by increasing desertification, deforestation, and denitrification.

===

 

...to summarize.

It is that trillion-(plus) tons of biomass--the soil, which can rapidly be changed--that (as you say) continues "through sheer volume, to say what happens in our air."

[maikeru]

Essay,

 

I do not agree that soil microbes have much to do with the composition of our atmosphere. The green plants that live by photosynthesis are what removes CO2 from the air - the rest of the life forms on our planet do the very opposite. And, as I have posted above, 97.2% of the plant life that scrubs the CO2 lives in the oceans. Desertification, intense farming, etc. all are unpleasant, but there just aren't enough land plants to affect CO2 levels much.

 

This is not correct. Soils and the atmosphere are interconnected, and affect each other in significant ways. Also, soils contain and often harbor significant amounts of cyanobacteria, algae, lichen, etc. that perform photosynthesis (and in the case of cyanobacteria can fix N2). Even in the case of deserts (and Antarctica), many have a crust of living lichen on the surface, where cyanobacteria/algae and fungi work together to fix N2, perform photosynthesis, and grow in some of the harshest places on earth. Also, I have some biochar-filled pots with herbs that I keep in my room that have significant cyanobacterial growth on the surface of the soils, which makes them visibly tinted blue-green or even somewhat slimey. These coexist and flourish with the plants and are probably happily photosynthesizing away. Here are a few links on soil microbiology and soil science to perk your interest if you're so inclined:

 

Soil crust - Wikipedia, the free encyclopedia (I'm familiar with this because I live in Utah and have seen cryptobiotic soil many times--it's common in the undisturbed desert areas, although it's very fragile)

Soil Bacteria | NRCS SQ

Cyanobacteria Photos

[engineerdude]

This is not correct. Soils and the atmosphere are interconnected, and affect each other in significant ways. Also, soils contain and often harbor significant amounts of cyanobacteria, algae, lichen, etc. that perform photosynthesis (and in the case of cyanobacteria can fix N2). Even in the case of deserts (and Antarctica), many have a crust of living lichen on the surface, where cyanobacteria/algae and fungi work together to fix N2, perform photosynthesis, and grow in some of the harshest places on earth. Also, I have some biochar-filled pots with herbs that I keep in my room that have significant cyanobacterial growth on the surface of the soils, which makes them visibly tinted blue-green or even somewhat slimey. These coexist and flourish with the plants and are probably happily photosynthesizing away. Here are a few links on soil microbiology and soil science to perk your interest if you're so inclined:

 

Soil crust - Wikipedia, the free encyclopedia (I'm familiar with this because I live in Utah and have seen cryptobiotic soil many times--it's common in the undisturbed desert areas, although it's very fragile)

Soil Bacteria | NRCS SQ

Cyanobacteria Photos

 

I think you folks are making this way way too complicated.

 

Look at it this way - if every bit of animal life disappeared, and the plants remained, we would still scrub about the same amount of CO2 from the air. With no animal life, the carbon from the dead plants would just sit in the soil once the plant decayed, and become coal or petroleum or whatever.

 

Certainly there is life in Antarctica, and in deserts - but that is irrelevant to this thread. My point is that over 97% of all plant life is in the oceans, not on the land - and that the Amazon forest makes up a small percentage of that even smaller percentage of land plant life. Thus, variances in thickness of the Amazon would have a negligible effect on atmospheric CO2 levels.

[freeztar]

I think you folks are making this way way too complicated.

 

The system being studied is very complex. It's not "us" that are making it complicated. It's our understanding and analysis that becomes more complex with each new bit that we learn scientifically. Any study of worldwide phenomena is inherently complicated.

 

Look at it this way - if every bit of animal life disappeared, and the plants remained, we would still scrub about the same amount of CO2 from the air.

 

Can you elaborate? A legitimate, scientific source stating this would be acceptable.

 

With no animal life, the carbon from the dead plants would just sit in the soil once the plant decayed, and become coal or petroleum or whatever.

Do you include bacteria in "animals"?

 

My point is that over 97% of all plant life is in the oceans, not on the land - and that the Amazon forest makes up a small percentage of that even smaller percentage of land plant life. Thus, variances in thickness of the Amazon would have a negligible effect on atmospheric CO2 levels.

 

I understand your logic, but when you post a specific number (97%), you need to back this up somehow. A quick search provided a legitimate source that claims a number very different from yours.

 

Approximately half of the photosynthesis on Earth occurs in the oceans, and the remainder on land.

NASA Study Solves Ocean Plant Mystery

 

If you can find other legitimate sources that come up with a different number, I'd love to see them. Otherwise, I'm more inclined to go with NASA'a quote of 50/50. :phones:

[Essay]

With no animal life, the carbon from the dead plants would just sit in the soil once the plant decayed, and become coal or petroleum or whatever.

 

Do you include bacteria in "animals"?

Yes, that sentence begs the question....

===

 

I'd wanted to reply but got sidetracked--and Maikeru and Freeztar seem to have summed it up nicely.

Still, I want to again emphasize the importance of that 1.5 Trillion tons of terrestrial "old" biomass.

===

 

Engineerdude,

Yes, the amount photosynthesized in a year is proportional to the amount of new biomass created by those photosynthesizers.

 

The important number to focus on however, is the amount of that new biomass which gets incorporated into the 1.5 trillion tons of old biomass--versus the amount of new biomass that simply cycles back into the atmosphere.

 

In addition to how much of the new biomass is being cycled into the old biomass, another important number is the amount of old biomass that is being disturbed, dried, or in whatever way destroyed--and thus adding anew the old carbon that had been sequestered in the terrestrial microbiome since the soil formed after the last ice age.

 

A small percentage change, or trendline up or down, in that terrestrial "old biomass"

which is more than an order of magnitude larger than any of the annual carbon pools

is going to affect our atmosphere more than the annual carbon cycles. IMHO