Friday, August 8, 2014
The Ages of Gaia: A Biography of Our Living Earth
Book Review: The Ages of Gaia: A Biography of Our Living Earth by James Lovelock
(Bantam Books 1988, 1990)
This was a fascinating read by the main proponent of the Gaia Hypothesis. It was his second book about Gaia. Lovelock is a keen scientist and seems a sensible fellow. The details of what Lovelock calls ‘geophysiology’ are explored. The earth paired with life can be regarded as a self-regulating system and life as a self-organizing system. Life seems to regulate several cyclical chemical systems throughout land, ocean, and atmosphere. Lovelock is also an inventor and prides himself in being an independent scientist. One of his main ideas is that evolution is more closely coupled to the environment than previously acknowledged. In more recent times, biologists have verified this idea through acknowledgement of evolutionary mechanisms like “niche construction,” (organisms alter environment to increase survival chances) which may be as important to evolution as natural selection. Gaian science is a systems view, with the goal being to promote the overall health of the system, thus planetary medicine. Much of this book is about chemistry. He notes that intricate geophysiological regulation systems evolved without foresight or planning and followed the rules of natural selection.
Lovelock’s first inkling of Gaia theory was when working on instrumentation design for early NASA moon and proposed planetary missions. His background being in medicine and biology he was soon involved in the task of detecting life on other planets and proposed that the best way to do so was to analyze their atmospheres. Planets with life would have different atmospheres than planets without life due to the chemical cycles and metabolism between land, ocean, and atmosphere. Lovelock and his colleague’s conclusion that Mars was lifeless due to its atmospheric composition was not at first popular but turned out to be correct. In these analyses in the early 1960’s the atmosphere of Earth and the beginnings of determining how it developed was compared to that of Mars. The fact that life in its various forms developed and regulates our atmosphere through various chemical cycles led to the development of Gaia theory. Earth as alive was a component of ancient cosmology and earth as an organism also had scientific precedents such as those of geologist James Hutton and the Ukrainian scientists Korolenko and his cousin Vernadsky. Eduard Suess first coined the term “biosphere” in 1875 when studying the
Lovelock asserts that geology and biology are so intertwined that they can
hardly be studied separately. He uses the term “geophysiology” to study earth
as a bio-system. Gaia theory is a theory of a living earth – but not in a
comparable sense to a sentient earth in human terms.
He points out that the question: “What is life?” is not so easy to answer. An organism is a collection of living things, organs and tissues. Organs are composed of billions of cells. Our very cells are communities of microorganisms that once lived independently, their energy-transforming components as mitochondria in the case of animals and in the case of plants, mitochondria and chloroplasts.
“Life is social. It exists in communities and collectives.” Physics uses the term colligative to describe properties of collections. Properties like temperature and pressure are the colligative properties of collections of molecules rather than of a single molecule. The constant temperature of the human body, called homeostasis, is a colligative property. Can ecosystems and Gaia also have colligative properties, their own homeostasis? This seems likely. Lovelock notes that Gaia is not synonymous with biosphere. Biology and geology are intertwined. The biosphere is the place, or part of Earth where life typically exists. The properties of Gaia, like those of the human body, cannot be discerned through individual species or populations. The homeostasis of Gaia involves “temperature, oxidation state, acidity, and certain aspects of the rocks and waters are kept constant, and that homeostasis is maintained by active feedback processes operated automatically and unconsciously by the biota.”
The 2nd Law of Thermodynamics – the conservation of energy – is discussed in terms of entropy, negentropy, and the production and consumption aspects of life that transfer energy. Lovelock was influenced by Erwin Schrodinger’s What is Life? where he noted that life exists within boundaries yet transfers energy with environment beyond those boundaries. In a sort of hierarchy there are also the boundaries of earth (such as the atmosphere), the boundaries of ecosystems (forests, etc), of beings (skin, bark), and of cells (cell membranes). In response to critics from the climate and microbiology disciplines, Lovelock writes:
“Life has not adapted to an inert world determined by the dead hand of chemistry and physics. We live in a world that has been built by our ancestors, ancient and modern, which is continually maintained by all things alive today.”
Lovelock here mentions two criticisms of Gaia that he addresses. First is that it is teleological as Richard Dawkins and Ford Doolittle argued – earth does not really regulate life as it would have to do it consciously. Second is that biological regulation is only partial, as climate scientist Stephen Schneider argued. Lovelock notes that Gaia is a “tightly couple system of life and its environment…” He includes a whole chapter on his theoretical construct, called Daisyworld, an imaginary world where different colored daisies evolve as the only life on a planet and alter temperature by their color. He made this model to show that self-regulation could come about through simple evolution and energy transfer through feedback mechanisms without any pre-conscious intent. To me this suggests that he is saying that Gaia is alive but not conscious. Variables in the Daisyworld model are temperature, solar luminosity, diversity, and color of the daisies (to absorb or reflect sunlight in order to regulate climate). He compares his imaginary construct to mathematical ecology models. He notes the difference between his geophysiology and theoretical ecology is in the interpretation of perturbation:
“The geophysiologists see temperature, rainfall, the supply of nutrients, and so on as variables that might be perturbed. In their view the Gaian system evolved with its physical and chemical environment and is well able to resist changes of this kind. Forests of the humid tropics are normally well watered and shaded by their canopy of clouds; during their existence they are never subjected to prolonged drought as in a desert region. Theoretical ecologists, on the other hand, ignore the physical and chemical environment; to them the environment means the collection of species themselves and a niche is some piece of territory negotiated among the species, …”
This is important as geophysiology suggests that the natural link between ecosystem and environment is strong, such that if that ecosystem were replaced (say tropical rainforests cut down for agriculture) then such a perturbation would be more difficult to recover from than the natural climatic variations of the previous ecosystem through time. Homeostasis would be harder to achieve. This, he says, is in accord with the “punctuated evolution” ideas (rapid and abrupt periods of evolution) of Stephen Jay Gould and Niles Eldridge. Gaia theory simply notes that life and environment evolve together. Biologist Alfred Lotka noted that modeling a whole system would be simpler than modeling parts of it. It is apparently more functional to do so as parts of systems are more liable to exhibit chaotic, non-linear behavior and relationships, says Lovelock. He gives four points about the Gaian view: 1) Life is a planetary-scale phenomenon, immortal in this sense with no need to reproduce; 2) partial occupation of a planet is not possible to sustain life (naturally) as sufficient life is needed to regulate the environment; 3) Darwinian adaptation notions must be altered to include the environment, which is tightly coupled to life; 4) models of species and environment as a single system are mathematically stable and show that increased diversity leads to better regulation.
Next the Archean (4.5 bya to 2.5 bya) is explored. Life is thought to have begun on earth 3.6 billion years ago. He makes an interesting point about the ability of life to pass on information better than any other means, further and with less distortion.
“There is every reason to believe that we share with the first ancient bacteria a common chemistry, and that the natural restrictions on the existence of those ancient bacteria tells us what the environment of the early Earth was like. By transmitting coded messages in the genetic material of living cells, life acts as a repeater, with each generation restoring and renewing the message of the specifications of the chemistry of the early Earth.”
Of course, the message mutated through time. The Earth as a body likely came from an exploding star, a supernova. This likely happened around 4.55 bya as dated through the precision of radioactive decay. Before life came about the planet was probably beset with violence in the form of multiple planetesimals and volcanic eruptions. Lovelock and his collaborators note that the atmosphere of a planet tells more about life than any other thing such as the rocks or the oceans. Certain components present together like methane and oxygen are related to life processes. The atmosphere has an immediate effect on the climate and chemical state of a planet. On earth the chemistry and climate were obviously favorable for the development of life. A cooler sun was offset by a thicker blanket of CO2. Lovelock does note that exact conditions in the Archean are unknown but much can be surmised about the atmosphere and its components. Much more frequent volcanic eruptions and reaction between ferrous iron from basaltic rock and water would make hydrogen gas. Hydrogen would have escaped from the atmosphere until biochemical reactions occurred with it in the ocean and later it reacted with oxygen in the atmosphere to form water. The dead bodies of the first microbes likely became food for the next ones as they were concentrated organic matter. It was also in the Archean that cyanobacteria, the primary producers, first learned to tap the sunlight for food by photosythesis. There were also methanogens, scavengers that rearranged the molecular products of the producers. In Lovelock’s scenario life came before Gaia. After microbes colonized most of the planet the regulatory processes affecting the entire biosphere could commence. Photosynthesizers used up CO2 but made oxygen which was immediately taken up by the oceanic oxidizers, sulfur and iron. The methanogens utilized organic material and made as waste products CO2 and methane but only in the absence of oxygen. Lovelock proposes that this may have produced a layer of methane smog very high in the atmosphere that had the same effect as the ozone layer does today – filtering ultraviolet light and stabilizing the stratosphere. He goes into much more detail about possible Archean atmospheric components but also cautions that his ideas here are quite speculative. The end of the Archean about 2.3 bya is marked by a fall in temperature and a sharp rise in atmospheric oxygen and a disappearance of methane. Planetesimals may have killed off half of the life on earth many times during the Archean but in each case life recovered. He thinks the presence of life has led to Earth keeping the oceans. He talks about much more here: carbon burial, hydrogen sulfide, anoxic zones, anerobic organisms, denitrification, and free oxygen. He thinks the point where free oxygen became present in the air signaled the end of the Archean. Bacteria was the only life in those 2 billion years. It was both mobile and motile – a single organism throughout the world exchanging information “as messages encoded on low-molecular-weight chains of nucleic acids called plasmids.” This was the first known global communication network.
We now come to the Proterozoic period of the Precambrian era (2.5 bya to 570 mya). As in the Archean the earth was populated by the bacteria known as prokaryotes but in the now mildly oxidizing ocean emerged a new form of bacteria, the eukaryotes. “These are the ancestors of large communities of nucleated cells, like the trees and ourselves.” The boundary between the Archean and Proterozoic is not set in stone. Lovelock likes to see it as the point in time when dominance by electron donors like methane gave way to dominance by electron acceptors like oxygen – which made the overall environment predominantly oxidizing. Now, instead of an excess of methane there came to be an excess of oxygen in the air – the environment went from anoxic to oxic. The composition of the atmosphere changed. He speculates that a fall in the atmospheric concentration of methane may have led to a known period of major glaciation 2.3 bya. Free photosynthetically derived oxygen in the air may have caused hydroxyl radicals to oxidize atmospheric methane and new consumers may have fed on organic matter before it could reach the anoxic sediments, denying them of their fodder to make methane. These would be positive feedbacks for the development of an oxygenated atmosphere. Lovelock suggests that as oxygen was crucial to the geophysiological development of the atmosphere so was calcium crucial to the geophysiological development of the oceans. Oceanic limestone deposits are apparently an adaptive strategy to quarantine potentially toxic ionic Calcium. This was first done by bacteria in the building of stromatolites and is now remnant in bone and teeth. Biological calcium carbonate deposition may have powered the endogenic cycle – the slow cycling of elements from the ocean surface to the crustal rocks and back again. This may have even spurred plate tectonics from the basalt-eclogite phase transition near subducting plate margins. This is apparently a speculative idea not accepted by most geologists but if true it would be powerful evidence for regulatory activity by living things. Even today there is new research suggesting that life had regulating effects on atmospheric and chemicals cycles such as the following geology article that suggests burrowing animals stabilized oxygen and phosphorus. This is thought to have begun at the end of the Proterozoic – about 540 mya as burrowing animals evolved. They affected the rate of carbon burial and the amount of carbon buried affects oxygen production as Lovelock notes. This sounds a lot like one of Lovelock’s ideas:
Next he talks about salt regulation. It is interesting that the salinity of the blood of most living things is remarkably similar. Too much salt affects cell membranes. Most sea creatures have evolved internal salt regulating mechanisms. Next he talks about how vast limestone reefs serves to trap water in lagoons, water which eventually evaporates and deposits the salts. This is another way oceanic salinity is regulated. He notes that the evidence for this is strong. He does note that the links between biomineralization (like biological deposition of calcium carbonate), salt stress, and plate tectonics are tenuous – but he seems to favor the idea. The new Proterozoic eukaryotes were communities of cells that utilized the presence of oxygen. Cyanobacteria are ancestors of the chloroplasts of plants and trees. Chloroplasts occur in eukaryotes as part of the community within the membrane in what is called endosymbiosis. The need to transfer genetic information, easier in the single-celled prokaryotes, now required a new process – sex.
Oxygen concentration affects growth of organisms and growth of organisms affect oxygen concentration. Where the lines intersect is the point of regulation = ~21% atmospheric oxygen – which has apparently been remarkably consistent – the geology article above suggests that it was helped by burrowing animals at the end of the Proterozoic when oxygen levels were noted to have risen to this level.
He gives an interesting account of a place in southern
Africa bout 1.8 bya where
algal mats processed and concentrated uranium isotopes coming from deposits
dissolved in a local stream – that served as a natural nuclear reactor! The
uranium isotope, could only be soluble in the presence of sufficient oxygen
which likely came about in that time period in that place.
We now come to the Phanerozoic which begins about 570 mya and goes to the present. Soft-bodied cell communities and skeletons came about just before this time. Reactions of free oxygen with other elements like carbon and sulfur would lead to acids in the air and increased weathering of crustal rocks, releasing more nutrients – another positive feedback , beneficial for life. Lovelock suggests that plants began to make lignin to detoxify oxygen by phenols reacting with it and locking it in – just as sea creatures made calcium carbonate to detoxify calcium. In both ways the poisons are captured and sequestered. In the case of calcium this made for vast cell communities – stromatolites, reefs. In the case of oxygen sequestering in these polymers, it allowed the development of plants and animals. Apparently, it has been shown that below 15% oxygen nothing could burn and above 25% oxygen it would burn everything – so about 21% is an interesting near-necessity for many forms of life. The presence of charcoal going back at least 200 mya shows that it was in this range. Fires themselves could theoretically also regulate oxygen by regulating carbon burial but there is apparently not enough charcoal in the rocks to account for this. He does speculate that it could have been regulated by more flammable trees with more complete combustion that don’t leave much charcoal
Next we come to the carbon cycle. Life certainly partially regulates carbon and carbon dioxide. It does this by speeding up the carbon cycle through increasing rates of rock weathering. Rocks are conveyed from plate margin subduction zones to mid-ocean ridges over millions of years in a continuous slow cycle. Life takes carbon dioxide from the air and brings it to the ground where it reacts with calcium silicate in rocks to form silicic acid and calcium carbonate which in turn are carried by streams back to the oceans to be used as shells then dropped on the sea floor to be subducted. Lovelock suggests that the most abundant vegetation occurs with the least atmospheric carbon dioxide - in periods of glaciation – which he suggests are the healthiest periods of Gaia. Some of these glacial periods have CO2 at the lowest level comfortable for plant life. In the Miocene, just 10 mya new plants developed that could tolerate lower CO2. These are called C4 plants and include some grasses. They tolerate the low CO2 periods of glaciation and are better prepared for the next glaciation. He thinks the glacial periods have the highest amount of life and the most efficient forms of life. The increasing heat of the sun and the effect of the Milankovitch cycles may trigger glaciation which he thinks is a regulating effect – the more normal earth-state with the inter-glacials like now being less healthy and abnormal. Lower sea level would mean more fertile ground exposed in the tropics to support tropical forests which would sequester more carbon and lower CO2. This is all speculative but very interesting.
Next he considers the sulfur cycle. Here Lovelock has done some key scientific work. Hydrogen sulfide was once thought to be emitted from the ocean in sufficient quantity to account for its uptake of sulfur among life but this is now known not to be the case. Lovelock invented a homemade gas chromatograph able to detect dimethyl sulfide and halocarbons (such as CFCs) in parts per trillion. This he took or sent on a few voyages across oceans to measure it. As an independent scientist he funded much of the research himself in the early 1970’s. The results of this research were published in the journal Nature. He found that halocarbons were persistent in the atmosphere. He also found that dimethyl sulfide and carbon disulfide were conspicuously present in the oceans. Dimethyl sulfide is emitted by algae as a result of their salt-regulating mechanism that involves betaines. The so-called smell of the sea is probably the smell of dimethyl sulfide. Lovelock’s Gaia theory suggested its abundance might account for sufficient atmospheric sulfur (as aerosols that eventually fall back to earth via air currents or rain) to account for the missing sulfur in the sulfur cycle and subsequent studies have proved this correct. He speculates on how this salt-regulating mechanism of algae came about through algae drying out, stranded on ebb tide beaches. Algae also release methyl iodide which carries iodine to the land which along with sulfur is essential for land life. The emission of sulfur by algae has also been proposed as an efficient climate regulating mechanism. Stratospheric sulfur gases from volcanoes are known to cool the climate as it forms sulfuric acid with water vapor around small particulate matter (also from volcanoes) that falls much slower. This cools the climate for a while until the aerosols drop. Some have suggested that the algae can emit dimethyl sulfide as a climate regulating mechanism but this is highly speculative. Apparently, it has been found that the sulfur chemicals related to salt regulation of algae are released eventually after their death and after it circulates through the ocean – as dimethyl sulfide, particularly in the “desert” areas of the open ocean – and this makes the aerosols that react to make sulfuric acid nuclei to form clouds. This increases wind velocity which mixes the nutrient-depleted surface zones and the nutrient-rich deeper zones of the upper part of the ocean – so the algae benefit themselves. The rain also washes out nutrient-rich land dust out of the air. The clouds also filter ultraviolet radiation. The atmospheric oxidation product of dimethyl sulfide is methane sulfonic acid which has been found in ice cores to correlate to global temperature which suggests that cloud cover and low carbon dioxide acted in unison to cool the earth.
Next he seeks to look at the problems of Gaia from the perspective of a planetary doctor. Some of this material is just a bit outdated. He gives an account of global warming from a late 80’s perspective. He talks about acid rain and how the problem is with dosage as some is natural. It also depends on where it falls – if on already acid land it brings the pH too low. He notes that perturbations caused by humans can upset the Gaian regulatory systems. Acids and other components from nitrate fertilizers and raw sewage also affects ecosystems, oceans and forests. Then his discusses ozone and CFCs. As stated earlier he invented an extremely sensitive gas chromatograph to detect CFCs in parts per trillion. These had thinned the ozone layer. More problematic is that they are intensely potent greenhouse gases. Lovelock originally thought that CFCs were harmless – he calls it a great blunder. He got caught in the politics and notes that the dangers of ultraviolet radiation are variable and with CFCs as with many other things the dose makes the poison. It was once thought that unfiltered ultraviolet light was lethal but experiments have shown that life has ways of adapting. He also discusses nuclear radiation and ecology. He notes that oxygen kills us the same way as nuclear radiation does by metabolizing oxidizing free radicals. Thus, oxygen is a mutagen and a carcinogen that confers on us a lifespan and we fight the same battle as was fought by life at the end of the Archean when oxygen began to increase. We evolved antioxidants like vitamin E, and other chemical neutralizing mechanisms like superoxide dismutase, catalase, and others to mitigate problems related to oxygen toxicity. He does note that our vast population of humans has given us the potential to cause harm on a much greater scale than previously. If there were only a billion people instead of 7 billion there would be less global warming, less pollution, etc. He derides “bad farming” as one of the biggest threats to Gaia. By this he means such things as deforestation for agriculture, intensive monoculture, and extensive grazing that minimizes diversity and carbon sinks.
In one chapter he examines imaginary scenarios of making Mars habitable for life. This is all very speculative and he does think that Mars is probably too dry to support life even with magnificent engineering feats like making a greenhouse atmosphere by manufacturing CFCs and unlocking the ice deposits for water – though those ice deposits may be much less than thought. He suggests that the only way for it ever to happen is to make it habitable for life and have life do it through its regulatory mechanisms over millions of years. This is all so very unlikely that even reading about it is a bit over the top.
The last section is titled God and Gaia. Since he was often asked much about his religious beliefs he included this chapter. He states that he was raised among counrty folk, witches, and Quakers. Though he admires religious festivities he is no religionist but a scientist. He does see Gaia as both a religious and a scientific concept but not in terms of any prevailing dogma. I suppose he enshrines mystery a bit, maybe similar to how Einstein stated it. He sees himself as a positive agnostic. As a Gaian he does seem to like the idea of a nature goddess, perhaps like the Virgin Mary is venerated among rural Europeans. He invokes William James and declares the scientist as inquisitive natural philosopher as religion enough, without the dogma. I like such a view. Lovelock acknowledges that we are the polluters, we demand and consume the products and resources that pollute. He has been accused by environmentalists as pro-industry but he says he is not. He simply thinks that Gaia is more powerful than what we can do to her. In extreme circumstances we could destroy our species and many others but the Gaia will recover.
He compares ideas of a deterministic and mechanistic universe and those of a self-organizing universe. He clearly favors the latter:
“It is concerned with the thermodynamics of the unsteady state of which dissipative structures such as flames, whirlpools, and life itself are examples.”
He sees the debate as a continuation of older debates between reductionists and holists and notes that reductionism will not fade away as a superb method for understanding and working with the components of things but seeing holistically can also solve problems and lead to deeper perspectives. He sees science being unnecessarily polarized by these one or the other views. Reductionism is key to the scientific method and needs to be free of subjectivity, yet we tread into areas where it breaks down and holism offers better ways of knowing. Systems are more than the sum of their parts, he notes. He notes his awe at chaos and non-linear systems:
“In our guts and in those of other animals, the ancient world of the Archean lives on. In Gaia, also the ancient chaotic world of dissipating structures that preceded life still lives on. A recent and relatively unknown discovery of science is that the fluctuations at every scale from viscosity to weather can be chaotic. There is no complete determinism in the Universe;”
Apparently the study of the thermodynamics of the unsteady state suggests the presence of a self-organizing universe.
In the epilog he talks about his home with his wife and pets in the country between
the changing of the local landscape to promote industrial farming and remove
troublesome wild critters, and the accompanying habitat destruction. It is the same in many places.
Lovelock thinks that if we see the world as a living organism which we are a part, then we will live in harmony better with it – rather than seeing ourselves as dominant over it or as a mere tenant of it.