'Energy flows and matter cycles' ; a secret to life and earth

part III Biodiversity regulates climate

Humans search for the grammar to understand life, ecology and earth. We seek a story to tell about ourselves and our a planet that is pulsing with living matter. Some scientists have been working at a complex systems framework to understand ecology and climate, that also captures some sense of the aliveness of it all. In the last article I covered a diaspora of these scientists developing this paradigm. It was a somewhat panoramic view, which some of you told me was quite breathtaking. It also covered a lot, so in this article I attempt to distill one of the central themes of this story into a simpler and more understandable form.

When water in a pot begins to be heated, the water molecules will increase their jiggling. As it gets hotter, billions of water molecules start moving upwards, carrying heat with it; heat which it will then release at the surface. In a cooler form, the water molecules will then dive back downward, where it goes to pick up more heat to bring back up. Heat flows upward, as the water circulates. Harold Morowitz, one of the first biologists to bring thermodynamics to his field, describes this as “Energy flows, matter cycles”. Dissipative structures, is what Ilya Prigogine called these matter cycles.

The circulation that happens in the pot, is similar to the convective circulation that happens in the atmosphere. The sun heats the surface of the earth, which causes air to rise, carrying heat with it. As it ascends it releases that heat. When cooled enough, the air then dives back down. Energy flows upward in the form of heat, while matter, in the form of air, cycles. The convection loop is a dissipative structure, which moves in a manner that allows it to release heat as fast as it can, in a maximum power manner.

The cycling air can carry water vapor with it. When water vapor evapotranspires from the land, it carries with it some heat of the land. Up in the sky, the water vapor condenses into clouds, where it releases that heat. The water then dives back down to the earth as rain. Heat flows up, as water cycles.

Another example of ‘energy flows, matter cycles’ is the tornado. When cold fronts collide with warm fronts, tornadoes may form. The lateral temperature gradient drives the flow of heat, which then helps drive the spinning of the tornado. There is also a vertical temperature gradient that drives the flow of air upwards. The flow of the energy from warm to cold helps drive the circulation of the air, creating the dissipative structure that is the tornado.

[ Diagram from UK meteorological service showing conditions for tornadoes]

Boris Belousov, was a Soviet chemist who discovered an intriguing chemical phenomena, that later became known as the Belousov–Zhabotinsky reaction. When he mixed cerium sulfate and some others chemicals, he found they formed these pulsing, evolving patterns. That’s not normally what we would expect in chemistry. We expect chemicals to mix, react, and then decay to a homogenous state.

When Belousov wrote a scientific paper about this reaction, journal referees would not permit it to be published, because they thought that the reaction violated the second law of thermodynamics, which says that entropy always increases.

It was Ilya Prigogine who solved this thermodynamic mystery of how order formed in the face of entropy, a discovery for which he would win the Nobel Prize.

If we think about our boiling pot of water example, that the water molecules move in large coordinated convective cycle is somewhat unexpected from the perspective of the law of entropy increase. We normally would expect a system evolves to more randomness, not to more coordinated motion. Heating the pot of water could have caused all the water molecules in it to get more energy and bounce in random directions at higher velocity. But they don’t bounce around randomly, they coordinate into these convective loops.

The reason the system is able to self-organize this way is because it expels entropy in the form of heat from the pot of water which means there is then more order left for the pot of water to self-organize with. In doing so, it can then transport heat at a faster rate, in a maximum power manner, to be expelled out of the pot of water.

What Prigogine discovered was that in a far from equilibrium system energy can flow out of the system, expelling entropy, which then allows more order to be in the system. The expelling of entropy drives matter cycles that are ordered. “Entropy is the price of structure” wrote Prigogine.

In the chemical reaction that Belousov discovered, as energy flows through the system, it drives a flow of matter, with cerium 4+ turning into cerium 3+ with the help of a catalyst, and then that cerium 3+ turning back into cerium 4+ with the help of another catalyst, thus creating these oscillating, evolving patterns. In the convection loop and the tornado matter cycle around spatially, in this chemical reaction case matter makes and unmakes itself in an autocatalytic cycle. Matter is flowing through a structural space. Like legos making and unmaking themselves. Energy flows, matter cycles.

As Prigogine’s nonequilibrium thermodynamics work spread, the Belousov–Zhabotinsky reaction became an archetypal example of how order can appear. It provided a simpler analogy for the Kreb’s cycle, aka citric acid cycle, the bane of many a medical student forced to memorize it. The Kreb’s cycle is a cycle fundamental to life, playing a key role in metabolism and the production of energy in organisms. As chemical energy flows in our bodies, it drives the Kreb’s cycle which consists of molecules unmaking and then making itself again, in an autocatalytic circulation of molecular matter. Energy flows, matter cycles. An organismal dissipative structure that helps organisms metabolize.

The ‘energy flows, matter cycles’ picture can shed light on what happens in earth’s ecosystems. Sunlight is transformed by plants into chemical energy that drives the plant-animal-bacteria-fungi cycle. Molecules are built up into more complex chains, and then broken down, only to be made up again. Plants make and unmake complex molecules. Animals eat plants and make new complex molecules out of the plant’s molecules. They then break down some of these molecules and poop them out. Fungi and bacteria then break down those molecules further, turning it into soil. Plants grab some of those simpler molecules from the soil, and then once again, make more complex molecules. Our ecosystem is a cycle of molecules making and unmaking each other, in a dissipative structure and autocatalytic cycle of organic matter. Transformed sunlight flows, matter cycles.

The plant-animal-bacteria-fungi-bactera cycle produces soil. The soil is better able to absorb the rain it falls down so it doesn’t all become runoff. The soil supplies water for the plants to evapotranspire and create rain, rain that then gets absorbed by the soil again. The plant-animal-fungi-bacteria cycle thus couples with the small water cycle. As transformed sunlight flows, it drives this coupled eco-water cycles.

Soil allows sunlight to be absorbed and reradiated over a wider range of time, through the night and sometimes even through winter. This means that photons are radiated back out into outer space in more directions, because of the earth’s spin. If photons are radiated in more directions it is more entropic. When water vapor transports heat to a higher altitude, the ensuing photons that radiate into space are longer wavelength and more entropic. Soil and water thus help expel more entropy into space, which means there is then more order available for the earth to self-organize.

This reservoir of self-organizing order is used by evolution to couple the plant-animal-fungi-bacteria cycle and small water cycle to work more in tune with each other. It also couples them with the oxygen, carbon, and nitrogen cycles, the process by which the gases flow into the atmosphere and then come back to be integrated into organisms.

In the process of this coupling, we have biodiversity adjusting the rain to meet its needs. And in the process we have biodiversity adjusting the temperature for optimality, because it can affect the heat capacity of the soil, enable evapotranspiration cooling, adjust the amount of water in the atmosphere that affects the formation of clouds, and affect the amount of greenhouse gases that are in the atmsophere. As energy flows through the earth, and matter cycles, the organismal matter cycles adjust the atmospheric matter cycles.

As our planet hurtles through space over the aeons, energy and matter have been self-organizing in ways to absorb more sunlight, and evolve to ever more complex forms. The sunlight is transformed to drive the autocatalytic cycles of matter that create multidimensional diverse networked forms, and to coordinate the pumping of water and gases into the atmosphere where they can be transported to be nutrients for these autocatalytic cycles. Its an earth evolving into a living organism.

………………….

Here is part I “ Adventures in Daisyworld”, and part II “Unifying ecology and climate with the fourth law of thermodynamics”, of this ‘Biodiversity regulates the climate’ series.

……

This is a reader supported publication