Conserving old growth forests is key to stabilising the Earth’s climate

From the Blog of the Club of Rome




© Greatandaman | Dreamstime
By Ugo Bardi, member of The Club of Rome


02 May 2023 – Do forests create rain? It is a question that has been debated for a long time. We know that trees produce huge amounts of water vapor that is pumped from humidity in the ground and condensed into clouds that generate rain, but the mechanisms that govern condensation and vapor water movements are still not completely clear.

In our new paper, a group of researchers led by Anastassia Makarieva of the Theoretical Physics Division of Petersburg Nuclear Physics Institute (PNPI) and the Institute for Advanced Study of the Technical University of München (TUM) highlight how evapotranspiration – the evaporation of water by trees, modifies water vapor dynamics to generate high moisture content regimes that provide the rain needed by land ecosystems. The research is a significant step forward in understanding the critical need to conserve old-growth forests to stabilise the Earth’s climate and maintain the biodiversity needed for the ecosystem to survive.

The study titled “The role of ecosystem transpiration in creating alternate moisture regimes by influencing atmospheric moisture convergence” shows that two potential moisture regimes exist: one is drier, with additional moisture decreasing atmospheric moisture import, and one is wetter, with additional moisture enhancing atmospheric moisture import. In the drier regime, that may be caused by deforestation, water vapor behaves as a passive tracer following the air flow. In the wetter regime, it modifies atmospheric dynamics and amplifies the atmospheric moisture import, creating rain.

There is still much that we need to understand about these mechanisms, but we are starting to understand how forests and the atmosphere form a system of connected elements that affect each other. One thing is clear: forests are crucial to the stability of the Earth’s climate.

Not only do trees store carbon in a form that does not cause greenhouse warming, but they actively cool the planet, due to how moisture condensation is managed. Forests also control the water cycle on land, pumping water vapor from the oceans inland by a mechanism called the biotic pump. Old growth forests generate giant flows of water known as “flying rivers” that fertilise entire continents. Our study shows that the non-linear precipitation dependence on atmospheric moisture content has wide-ranging implications. Atmospheric water flows do not recognize international borders, meaning deforestation disrupting evapotranspiration in one region could trigger a transition to a drier regime in another.

Our results indicate that the Earth’s natural forests, in both high and low latitudes, are our common legacy of pivotal global importance, as they support the terrestrial water cycle. Their preservation should be a recognised priority for our civilisation to solve the global water crisis. Important on-going work calls for re-appraisal of the forest’s role in the global temperature regime.

The study was performed by an international research team that included scientists from North and South America, and Eastern and Western Europe.

Rain is Life, and Holobionts Create it

 

Buying vegetables at a stall in Florence on a rainy day. My wife, Grazia, is the one with the pink umbrella. 

By Ugo Bardi

After three months of drought during the summer, Florence is now drenched in rain. It has been raining for two months and people are complaining that it is too much! But it is how things have to be: I recently discovered that rain is an "autocatalytic" phenomenon. A more humid atmosphere creates more rain, and rain creates a more humid atmosphere. And that creates long periods of static weather -- too little rain and then too much. 

I learned that from the work of Anastassia Makarieva, Mara Baudena, and several others who have studied the relationship between atmospheric humidity and rain. Look at this figure, from a paper by Makarieva et al., to be published.

The y-axis is the amount of rain, in mm/hour. The x-axis is the amount of water vapor in the "air column." Note the strongly non-linear relationship. It is a typical power law: a small increase in atmospheric humidity causes a large change in rainfall. The three red points indicate the boundary of the "abiotic regime" (no rain) and the power law region.  

As I said, it is an autocatalytic phenomenon, Rain tends to generate more rain, at least as long as it wets the land and it generates moisture transpiration, which increases the water vapor content in the atmosphere. This has very practical consequences in many senses. One is the role of forests in weather and climate. Forests generate strong evapotranspiration, that is they pump water from the soil to the atmosphere. And, also, forests tend to keep water in the soil, slowing down the runoff.

So, not only do forests generate rain, but they also tend to maintain the rain pattern. Without forests, and with the land covered with buildings, you have the typical desert climate: dry most of the time, then with short periods of heavy rain. Disasters ensue, now a common pattern in areas such as California or Italy, where deforestation has taken place. 

So, we need our fellow holobionts, the trees. Onward, fellow holobionts!

(below, some rain-loving holobionts pictured together)

Forest Recovery: A quote by Anastassia Makarieva

 

You see, there is a succession process for forest recovery. We first have shrub grasses after some disturbance like fire, then it takes time for that to be replaced by trees. So if we are lucky, our grand grandchildren will be walking in such a forest, so this dimension should also be stressed. We are working for the future we are not just securing for ourselves some two dozen years of better comfort. Rather, we send a message through centuries such that people will remember us, and walking into this forest along the brooks and rivers they will remember us with gratitude for our care and dedication.

Anastassia Makarieva  

The Role of the Forest Holobiont in Earth's Climate: More Important than it was Believed so far

Above, the talk by Anastassia Makarieva at the International Conference on Basic Science for Sustainability in Belgrade, on Sep 22, 2022

It is about an innovative and important interpretation of the current climate situation. Anastassia is proposing that the warming of the atmosphere may be caused not just by the accumulated CO2, but by a radiative forcing of the same order of magnitude generated by deforestation. Earth's forests are giant holobionts coupled and embedded in the even larger holobiont that's the whole ecosystem. It is not surprising that they strongly affect climate, and not just by the conventional factors, albedo and carbon sequestration. There is much more than that, as you can learn by watching the clip, above.  

I don't have to tell you the consequences of this concept. If it turns out to be true (and I think it might well be), it means that we have done a lot of wrong things in trying to mitigate global warming, for instance proposing "biofuels" obtained from wood. But there is much more: it is a complete revolution in the way we see Earth's climate system. Forests not only cool the atmosphere, but also stabilize the climate. This means not only that we need more forests, but that some ideas such as carbon sequestration and geoengineering could do a lot of damage if not coupled with reforestation.

On the other hand, Anastassia's ideas could also be misunderstood as meaning that Climate Science, as it has been proposed so far, is all wrong. And that's sure to happen if her ideas come into the hands of politically minded people who would use that to propose that there is no such thing as global warming, climate emergency, etcetera.  But if we believe in Science (true science, not TV science) we must not be afraid of the truth.

Onward, fellow holobionts!

Forests: do they cool Earth, or do they warm it? A comment by Anastassia Makarieva

 

Anastassia Makarieva, giving a talk. Together with Viktor Gorshkov, she developed some fundamental concepts on the functioning of the ecosphere: the "biotic regulation of the environment" and the "biotic pump." Here, with her permission, I reproduce a message that she sent to a discussion forum on these matters. If you are interested in joining the forum, write me at "ugo.bardi(thingette)unifi.it"

by Anastassia Makarieva

Dear colleagues,

thank you very much for these fascinating discussions. I am learning so much from this group, just to mention a couple of more recent things, thanks Svet for reminding us of those important mice studies, thanks Mihail for the note about agroecology in North Korea and thank you, Christine, for sharing your experiences as a farmer. It is indeed a very hard job, I am no farmer but I lived in the wild where you have to care about most things that are vital, and this job leaves little time for doing science, especially in a cold climate. (you can find some photos here). And I am overwhelmed with more things discussed in the group, trying to catch up, and will write later.

Here I thought that I would share my understanding of whether the forests cool or warm the Earth, I did discuss it a few times so sorry if it is a repetition.

In the review article recently quoted by Ugo, as Mara rightly noted, there is nothing controversial or revolutionary. Everybody knows that when a certain part of solar energy is captured by evaporation, the surface gets locally cooler than in the absence of this process. Just because, by energy conservation, a certain part of solar energy, instead of heating the surface, is spent to extract water vapor molecules from the liquid phase by overcoming intermolecular attraction.

But, importantly, this energy remains in the biosphere -- unlike the part of solar radiation that is reflected back to space by a bright surface.

So, whether the Earth as a whole will get cooler or warmer in the presence of evaporation, will depend on how the biosphere dispenses this latent energy.

Take a look at this figure, above. It shows how condensation occurs in the rising air. The latent heat is released in the upper atmosphere and can radiate to space from those upper layers without interacting with greenhouse absorbers (that are mostly concentrated below). This will serve to cool the planet, by effectively making the planetary greenhouse effect smaller. Once again: a certain share of solar energy will leave the Earth with less interaction with the greenhouse absorbers. It is a cooling effect of evaporation.

Importantly, this effect will be stronger if the warm air spends more time in the upper atmosphere. If it descends shortly after condensation, all latent heat becomes sensible and just warms the surface. But if there is a large-scale circulation pattern with the air traveling thousands of kilometers, the effect will be more pronounced. So the biotic pump circulation will make this effect stronger (more than in a local shower). (*)

But, besides this cooling effect, there are warming effects. One of them is the mere presence of more water vapor in the atmosphere over moist surfaces. Since water vapor is a greenhouse substance, its presence over land increases the concentration of greenhouse absorbers. The share of energy leaving without interacting with them increases, but the total number of molecules increases as well. Which effect will win?

Furthermore, more water vapor and convection mean more clouds. And some of the cloud types warm the Earth. Others cool the Earth. Which will prevail?

These arguments show why the message about cooling by forests will never spring up from global climate models. They are not suitable to estimate whether it exists and how strong it might be.

My personal position is that focusing on cooling or warming is strategically harmful to the forest protection case. What natural forests definitely do is that they minimize the fluctuations of the water cycle, heat waves, droughts, and floods. While these extremes are currently officially attributed to CO2 emissions, it is well-known that this attribution suffers from many problems. I would recommend this short video by Dr. Sabine Hossenfelder https://www.youtube.com/watch?v=KqNHdY90StU on this topic.

So in fact to argue that a particular (LOCAL) heatwave has to do with forest destruction (which is known to severely change LOCAL temperatures) might be much easier and more productive than to argue about the role of forests in global warming or cooling -- where there is no simple argumentation.

So, think how it works now: we have a heatwave, and people are told it is due to CO2 emissions, to cut emissions people use "biofuel" by cutting more forests. With more natural forest loss, the water cycle is further disturbed and we have more heatwaves, which are again attributed to global warming, etc. It is a complex situation.

Anastassia

Anastassia Makarieva on the role of forests in Earth's climate

 

If you can, do spend half an hour to watch the talk that Anastassia Makarieva gave at the Technical University of Munich (TUM) on 24.11.2021.

It is not easy stuff if you are not familiar with the field of atmospheric water circulation, but it is worth making the effort. Anastassia and her colleagues are doing nothing less than revolutionizing the way we understand the role of forests in the ecosystem. Rather than being a passive entity for humans to make chairs and cricket bats, forests may actually be what makes life on Earth possible, they are part of the great planetary holobiont that uses forests to regulate itself. 

Anastassia Makarieva Speaks About the role of Forests in Protecting Earth's Climate

 

Anastassia Makarieva in a recent talk recommendsed the preservation of the natural forest holobiont:

International climate discourse mentions forests in two contexts: as carbon deposits and as renewable sources of materials and energy.

If implemented in global policies, this narrow view on forests can, contrary to expectations, worsen climate destabilization. Two crucial aspects are undervalued and understudied.

The first is the major role of forests as regulators of the various aspects of the water cycle, including cloud cover (a major source of climate uncertainties) and ocean-to-land and transcontinental transport of atmospheric moisture.

The second is the difference in the environmental functions of primary forests, largely unperturbed by anthropogenic activities, versus exploited tree stands. While the former have evolved to maximize environmental homeostasis, the latter were selected to maximize economic productivity. The two cannot be maximized simultaneously.

Successful strategies of climate change mitigation should prioritize preservation of still extant self-sustainable natural forests for humanity to continue benefiting from their climate stabilization potential.

How Will our Descendants Remember us?

 

You see, there is a succession process for forest recovery. We first have shrub grasses after some disturbance like fire, then it takes time for that to be replaced by trees. So if we are lucky our grand grandchildren will be walking in such forest, so this dimension should also be stressed. We are working for the future we are not just securing for ourselves some two dozens years of better comfort. Rather, we send a message through centuries such that people will remember us and walking into this forest along the brookes and rivers they will remember us with gratitude for our consciousness and dedication.

Anastassia Makarieva 

A Fellow Feathered Holobiont

A fellow holobiont. This owl was photographed by Anastassia Makarieva in the region of the White Sea, in Northern Russia. It appeared to be friendly.

Owls have been fascinating as symbols of wisdom to humans since the time when they were sacred to the Goddess Athena. Anastassia sent to me this specific picture after a discussion we had on the meaning of the owl mentioned in an old short story by Vladimir Dudintsev, "A New Year's Tale" (1960) that resonates of meanings still valid today. I discuss this story in a post of mine on "Cassandra's Legacy"

Amont other things, it is curious how the symbology of owls was revisited by Hayao Miyazaki in recent times in his movie "Princess Mononoke"(1997) in the form of the little white creatures called "kodama," Japanese tree spirits. In the movie, kodamas share with owls the capability of turning their heads around, apparently without any bounds. You can see one of Miyazaki's kodamas as the front cover of this blog