The Roman Philosopher Lucius Anneaus Seneca (4 BCE-65 CE) was perhaps the first to note the universal trend that growth is slow but ruin is rapid. I call this tendency the "Seneca Effect."

Friday, March 17, 2023

How Forests Create Rain: a New Study on the Effect of Evapotranspiration

From the "Proud Holobionts" blog
Image created by Dall-E

The idea that forests create rain has been known by peasants for hundreds, perhaps thousands, of years. The first scientific studies go back to Alexander von Humboldt (1769–1859), but the subject remains controversial. Nevertheless, we are starting to understand the deep and complex interactions between the atmosphere and the biosphere. They form a true "holobiont," a system of connected elements that affect each other in non-linear ways. A recent paper published by a research group led by Anastassia Makarieva shows how evapotranspiration, the evaporation of water by trees, modifies the water vapor dynamics and may generate high moisture content regimes that provide the rain needed by the land ecosystem. There is still much that we need to understand about these mechanisms, but one point is clear: forests are a crucial element of the stability of Earth's climate, and they must be preserved as much as possible (U.B.)

Press Release, 14/03/2023

As water scarcity globally grows, and deforestation threatens the remaining natural forests, understanding how vegetation impacts the water cycle becomes increasingly important.  In their new paper, “The role of ecosystem transpiration in creating alternate moisture regimes by influencing atmospheric moisture convergence” published in Global Change Biology (, an international and interdisciplinary team led by TUM demonstrated the existence of two potential moisture regimes – one drier, with additional moisture decreasing atmospheric moisture import, and one wetter, with additional moisture enhancing atmospheric moisture import. In the drier regime, water vapor behaves as a passive tracer following the air flow. In the wetter regime, it modifies atmospheric dynamics.

The team based their analysis on the previously established non-linear dependence of precipitation on atmospheric moisture content – increasing absolute humidity leads to a negligible precipitation increment if the atmosphere is dry, but to a large increment when the atmosphere is sufficiently wet. Combining this dependence with a full consideration of the water budget, the researchers showed that an increase in precipitation in humid conditions facilitated by increased evapotranspiration, should lead to enhanced moisture import. They illustrated these patterns with the data from the Amazon basin and the Loess Plateau in China.

Dr. Anja Rammig (TUM School of Life Sciences and study author) considers these results as having profound implications for the ongoing studies of the resilience of the Amazon forest in the face of the danger of deforestation and climate change. Dr. Scott Saleska (University of Arizona, study author) believes that the new results are in agreement with the profound role of leaf phenology in the Amazon forest for water cycle regulation. By forcing a decline in forest evapotranspiration, deforestation can dehumidify the atmosphere and thus drive the forest into the drier regime where transpiration of the re-growing vegetation would further aggravate aridity by decreasing moisture import. Getting out of this landscape trap could be impossible. Dr. Ruben Molina (University of Antioquia, Colombia, study author) hopes that the study findings will raise the awareness of the importance of tropical forest conservation.

Dr. Andrei Nefiodov (Petersburg Nuclear Physics Institute, Russia) participating in the study says that the new results corroborate the concept of the biotic pump of atmospheric moisture that emphasizes the dominant role of natural forests in transporting moisture inland. Dr. Antonio Nobre (INPE, Brazil, study author) compares this biotic moisture pumping to a beating heart, and highlights the good news: even in arid lands, by restoring the vegetation one should be able to enhance the atmospheric moisture convergence and streamflow. To achieve that, the ecological restoration strategy should be carefully designed to guide the ecosystem transition from the dry to wet regimes.

“I suspect that natural vegetation will be best for maintaining a moist and productive environment as these systems kept the world green and productive long before people got involved” – emphasizes Dr. Douglas Sheil (Wageningen University, author), collaborating on the research. “We do need to take into account the holobiontic relationships among all ecosystem elements that allow for an efficient regulation of the water cycle,” adds another author Dr. Ugo Bardi (Club of Rome, University of Florence).

Anastassia Makarieva (Institute for Advanced Study, TUM, lead author) emphasizes the need for a broad international cooperation in the studies of the ecology of the water cycle: “We have shown that the non-linear precipitation dependence on atmospheric moisture content, first noted by our co-author Dr. Mara Baudena (CNR-ISAC, Italy) and her colleagues, has widely ranging implications. The atmospheric water flows do not recognize international borders, thus deforestation disrupting evapotranspiration in one region could trigger a transition to the drier regime in another. Our results indicate that natural forests of the Earth, in both high and low latitudes, are our common legacy of pivotal global importance as they support the terrestrial water cycle. Their preservation should become a widely recognized priority for our civilization to solve the global water crisis.”

Makarieva, A. M.,  Nefiodov, A. V.,  Nobre, A. D.,  Baudena, M.,  Bardi, U.,  Sheil, D.,  Saleska, S. R.,  Molina, R. D., &  Rammig, A. (2023).  The role of ecosystem transpiration in creating alternate moisture regimes by influencing atmospheric moisture convergence. Global Change Biology,  00,  1– 21.


  1. Walter Jehne, a soil microbiologist from Australia has a fantastic understanding of how hydrology and biological life interact,
    he says that two things form the nucleus of rain drops, salt crystals over oceans and certain airborne bacteria released by trees and plants over land,
    so forests transpire moisture and also release these airborne bacteria that seed the raindrops, the volume of rain that falls on the Amazon forest grossly exceeds the amount of water that exits the Amazon river into the ocean, because the rain is constantly falling, being transpired, seeded and falling again,

    I watched one of his presentations, he's quite modest and unassuming but he's got an answer for everything!

    I completely overhauled my understanding of the problem and the solution after discovering this guy,
    he answered all my outstanding questions.

  2. This is why afforestation would be possible in the Sahara and Australia.

  3. Forests evolved to retain rain and evaporate it out in place. A few hundred years of R & D and the evaporation is at a minimum and retention is maximum. Best not to improve it. Best to preserve it.

    1. I meant a few HUNDRED MILLION years of R & D for mother nature. A few hundred years of R & D is only human hubris.

  4. US$1.7 billion to build Ilısu Dam and US$1.2 billion to build Atatürk Dam in Turkey - prove how WMDs can be built at best, and how low humans can go ethically, morally and intellectually

    Watch here some of the impact caused:
    And here:

    The two US$ amounts combined is a fraction of what a conventional military system, like say an anti aircraft defence system, usually cost...

    Iran is now 30+ years trying to enrich Uranium - as the story goes - dedicating huge resources for the project.

    The West has spent no less resources - opposing the project - ha ha ha....

    Iran has already blocked all rivers going to Iraq, no less than Turkey - the West remained silent - ha ha ha

    The power generated from both dams in Turkey combined are hardly enough to run one or two Toyota or Renault car factories in Turkey - knowing most of the power would be lost before reaching the 1000s KMs-away - points of use.

    Voices in the ME and Europe have linked the vast amounts of water blocked behind the two dams and earthquakes recently hit Turkey.

    This far, few experts speculate that from now on - certain positions of the moon in its orbit will definitely cause more earthquakes - as if the system becomes an WMD.

    Humans were not ready morally, ethically and intellectually to start mass extraction of fossil fuels with the steam engine 300 years ago...

    The Magna Carta indeed requires now overhauling - adding to it the right for humans to understand what Energy really is;

    "In any system of energy, Control is what consumes energy the most.
    No energy store holds enough energy to extract an amount of energy equal to the total energy it stores.
    No system of energy can deliver sum useful energy in excess of the total energy put into constructing it.
    This universal truth applies to all systems.

    Energy, like time, flows from past to future".


  5. Unfortunately, most forest projects don't have even a few hundred years total, much less for R & D alone. ArtDeco