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Articles and Presented Papers

ABSTRACT. The goal of this paper is to formalize better the division of big history into three main stages (phases, eras). In my own work they are “dynamical realms,” 1. physical laws, 2. biological evolution, and 3. cultural evolution. I show a deep similarity in two mighty transitions; first, from dynamical realm 1 to 2, and then from 2 to 3. The common “metapattern” in these transitions is that of generalized evolutionary dynamics, which in both cases opened up vast new arenas of possibility space. I first present relevant conclusions from my book, Quarks to Culture. A “grand sequence” of twelve fundamental levels was forged through a repeated cycle of “combogenesis” spanning the dynamical realms as families of levels. Next, I provide examples of other scholars who have similarly weighed in on a three-fold arc; notably Christian, Spier, Chaisson, Rolston, Salk, and Voros (following Jansch). Like me, all have nominally recognized similarities between biological and cultural evolution as important in the dynamics of realms two and three. Generally, these scholars have not placed primary emphasis on general evolutionary dynamics as a multiply-instantiated process. The PVS metapattern for evolution (propagation, variation, and selection) is well established as overarching across many patterns in biology, following life’s origin. In culture the operation of general evolutionary dynamics is, I suggest, dual-tier, consisting of cognitive PVS of individuals coupled to social PVS of groups. The emergence of realm-forming PVS-dynamics twice (biology, culture) created radically new ways to explore and stabilize patterns in expansive fields of diverse types within the respective dynamics. Thus, we can recognize a fundamentally similar reason (i.e., two emergent forms of evolutionary dynamics) for why so many scholars have correctly, in my opinion, discerned a threefold arc of big history. Important as well in the flow of progress from quarks to culture were two only slightly less major instantiations of PVS-dynamics (though both crucial): an era of chemical evolution within the realm of physical laws, which led into the realm of biological evolution, and also the evolution of the animal cognitive learning PVS of trial, error, and success, which was essential to the path into cultural evolution. In concluding remarks, I note several outstanding issues: alternative proposals for five orders or four dimensions (i.e., divisions more than three in the arc of big history); the use of the word “evolution,” and three matrices (cosmosphere, biosphere, civisphere) that contain and are constituted by the varieties of patterns within the corresponding dynamical realms.


  • Volk, T. (2016). Biosphere. In J. Adamson, W. A. Gleason, and D. N. Pellow (Eds.), Keywords for Environmental Studies (pp. 32-34). New York: NYU Press.


  • Volk, T. (2010) It’s not the entropy you produce, rather, how you produce it. Philosophical Transactions of the Royal Society Bulletin, 365, 1317-1322.

ABSTRACT. Civilization can be at least partially determined by climatic constraints upon net primary productivity and heat dissipation from the human body (Kleidon 2009). I discuss how these “metabolic” limitations were historically overcome: first, because large rivers in dry regions provided water to ancient civilizations; second, because fossil fuel energy servants working externally to muscle-limited bodies have produced economic well-being in a number of world areas.


ABSTRACT. The biosphere is the thin, interconnected system of all living things and three environmental matrices of atmosphere, ocean, and soil. Organisms are coupled to each other in the traditional ecological interactions, such as the food webs. But organisms are also coupled by nutrient intakes from the matrices and waste inputs to the matrices. All together, these intakes and inputs create a global metabolism. The result is a biosphere system in which wastes from certain biochemical guilds of organisms are nutrients for other guilds, and in which free by-products from different guilds have affected the large-scale chemistry and thus habitability of the biosphere’s environmental matrices. Today, humans, through the combustion of fossil fuels and the waste emissions of the greenhouse gas carbon dioxide, are altering the chemistry of the atmosphere and the other environmental matrices, faster than the global carbon cycle can adjust. We are responsible for these changes, which will cause ever more global warming and other effects, and therefore we must look for ways to create a more sustainable future.


  • Volk, T. (2009). How the biosphere works. In E. Crist & B. Rinker (Eds.), Gaia in Turmoil: Climate Change, Biodepletion, and Earth Ethics in an Age of Crisis (pp. 27-40). Cambridge, MA: MIT Press.


ABSTRACT. In part I of this paper set, Volk and Bloom discuss the reasons why metapatterns are important in biological and cultural contexts. Here, in part II, we show how metapatterns can be applied to an important problem in qualitative educational research: the difficulties in elucidating fundamental patterns of interaction. In meeting this challenge we provide a metapatterns-based framework for analyzing and interpreting qualitative data. We begin by acknowledging the importance of context, the setting within which any system under investigation can be expected to exhibit metapatterns as functional components that are vital for the maintenance of that specific system within a particular context. We follow this discussion by defining three dimensions of our proposed analytical framework. The first dimension, which we call depth, examines the various metapatterns involved in the particular system under investigation. Extent is the second dimension, which involves extending to other contexts the interacting sets of metapatterns found in the investigation of depth. The third component is abstraction, which involves generating overarching principles or models from the analytical results of the first and second dimensions (i.e., depth and extent). We recommend that these three dimensions should be used recursively to meet the challenge named above. We demonstrate the framework through an example of a classroom discussion involving children arguing about the concept of density. We conclude with a discussion of the implications of this analytical framework, along with a list of fundamental principles of this framework and a list of questions that can guide qualitative research.


ABSTRACT. We justify the concept of metapatterns as functional patterns or functional principles that are common to a large set of systems that encompass both biology and culture, by starting with the fact that evolved systems, whether biological or cultural, are produced from any iterative sequence of replication, variation, and selection. Therefore the systems that result, with specific functional parts, are formed as wholes that fit particular contexts. The principle of convergence in biological evolution, in which similar structures are independently evolved, is the model that can be extended even beyond biology. If the contexts of evolved systems across widely separated scales are similar, the resulting evolved systems can exhibit convergences that themselves occur at diverse scales. These grand convergences are the metapatterns. For example, the functional advantage of dynamically separating systems from their environments sets the context for the evolution of the metapattern of borders across various scales. We outline fifteen additional examples of metapatterns. We also examine the correspondences and differences between metapatterns as a multi-scale approach to systems and the approach from complexity science. We suggest that metapatterns could serve as tools for thinking about a diverse range of topics, and could thereby motivate the transference of generalizations. Finally, we propose that because metapatterns are employed in human thought, they will be useful in formulating new questions for education research, which is the subject of the companion paper.


ABSTRACT. Purpose – Gregory Bateson defined a metapattern as a “pattern of patterns.” But, what did he mean by metapattern (which he used only once)? Can there be a meta-science, in which metapatterns are its objects or principles? The authors explore these issues. Design/methodology/approach – The authors review examples of Bateson’s “great pattern” of “combination,” which the authors call the binary. Bateson showed that binary is the minimal solution to the problem of gaining new characteristics by combining parts into a larger whole. Thus, binary is clearly a metapattern, a discipline-transcending structural and functional principle. The authors select parts of Bateson’s writings to highlight his search for other great patterns, some of which correspond with those developed by T. Volk. Findings – The authors suggest that the basis for a science of metapatterns is the following: functional patterns that confer advantages on the systems that possess those patterns can converge, in a meta-realm that includes all of what Bateson termed stochastic sequences, namely, in biological, cultural, and cognitive realms. The convergences are common solutions to the same functional problems that span a wide variety of systems. Other general principles in the organization of systems, such as borders, arrows, cycles, centers, and networks, constitute members of a system of metapatterns, the objects in a Batesonian metascience. The authors show that the metapatterns have implications for research in the humanities and social sciences, as well as for dynamic learning along the lines of Bateson’s broadly-extended concept of epistemology. Originality/value – As nearly universal functional patterns, metapatterns could serve to create a scale-bridging form of descriptive scholarship and thus contribute to the quest for a unified body of knowledge, which E.O. Wilson termed Consilience. Keywords Cybernetics, Sciences, Systems theory Paper type Conceptual paper


ABSTRACT. Axel Kleidon (Clim Change 66:271–319, 2004) proposed that the organisms that constitute Earth’s biota have free parameters that can be selected to create states of maximum entropy production (MEP) on various scales, from the biota to the planetary radiation balance of the Earth system. I show that Kleidon’s concept, here called the biotic-MEP hypothesis, is fundamentally mistaken. A thought experiment with a life form that would be selected against even though it would generate a higher degree of entropy demonstrates my case: A hypothetical tree that puts forth a non-productive but high-entropy producing black carpet of tissue clearly separates out entropy production from other biological processes and shows that entropy production is not a functional adaptation and therefore it cannot be selected for. A real world example comes from dimethyl sulfide-emitting plankton, which, by increasing cloud albedo, do not raise but rather lower the entropy flux of the Earth system. I provide a number of other examples of biotic processes that individually either decrease or increase the environmental entropy production. It is argued that biological effects on environmental entropy production can be expected to include both positive and negative examples, because these effects are merely by-products of the actual processes that are selected for by evolution. Given my framework of entropy production as a by-product of the true processes that are being selected for, the concept of MEP on environmental scales has no great relevance for discussions of biological evolution or the time history of the effects of life on the global system.


ABSTRACT. I offer here an essay of personal history of grappling with Gaia theory, with conclusions. These are as follows: The relatively steady states in the global environment are simply the expected, natural results of a system containing chemical reactions, many of which involve life. There is nothing special about the existence of both positive and negative feedbacks in this system; these are to be expected. Certainly much of the global environment has been, and is being, transformed by life into a state very different from that of a planet without life - but what is this state? I suggest that the global environment is, in essence, a waste-world: a system of by-products (and their effects). This wasteworld plus life creates a complexly structured dynamical system, because life is not passive. Organisms make metabolic products aimed to ensure their success at living and reproducing, not aimed at transforming or controlling the global environment. But in making these products, organisms also produce by-products, and these often build large-scale environmental side effects. The environmental consequences of the by-products are inadvertent but do create a system with evolutionary and population feedbacks - for instance, the biogeochemical cycles. The dynamics of this system are such that some forms of life alter the environment, and then all other forms within that altered environment must adapt or perish. Life thus shoves the environment around, subject to limits at various extremes. Are there general principles of the wasteworld? At the end, I spell out some directions that I see for the future of Gaia theory.



ABSTRACT. Lovelock’s Gaia hypothesis was born out of his insight that the atmosphere of a lifeless planet would be close to chemical equilibrium, while the robust presence of life would generate measurable disequilibrium. Others have expanded this view to postulate the growing disequilibrium of the Earth’s surface system from life’s influence over geologic time.

We show that the carbonate-silicate geochemical cycle (Urey reaction), the long-term control on the steady-state atmospheric carbon dioxide level, is far from equilibrium on the 'present Earth, approaching this state only on a billion-year timescale in the future as solar luminosity and surface temperature climb. Moreover, the progressive increase in the biotic enhancement of chemical weathering in the last 4 billion years, culminating in the weathering regime of the forest and grassland ecosystems, has brought the steady-state atmospheric carbon dioxide level closer to the Urey reaction equilibrium state. In contrast, the abiotic steady state is always further from this equilibrium state than the biotic, except near the origin of life and at their future convergence. These are counterintuitive results from a classical Gaian view.

Equilibrium is an apparent attractor state in biospheric evolution for the case of the Urey reaction and long-term atmospheric carbon dioxide levels, but apparently not for other atmospheric gases, especially oxygen.

Finally, an astrobiological flag: Lovelock’s original insight may still be valid for some cases, but far-from-equilibrium abiotic steady states may arise on Earth and other planets, and should not be taken as a priori evidence for Gaian self-regulation.


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  • Volk, T. (2003). A river runs through it (A scientist’s brush with death renews his connection to all life). Science and Spirit, 14, 2 (Mar.-Apr.), 50-53.

  • Bloom, J.W. & Volk, T. (2003). The use of metapatterns as analytical, design, and conceptual frameworks. Pre-conference workshop, Annual meeting of the National Association for Research in Science Teaching. Philadelphia, March 23.




ABSTRACT. A layered canopy model was used to analyze the effects of diffuse light on canopy gross photosynthesis in controlled environment plant growth chambers, where, in contrast to the field, highly diffuse light can occur at high irradiance. The model suggests that high diffuse light fractions (~ 0.7) and irradiance (1400 pmol m-2 s-1) may enhance crop life-cycle canopy gross photosynthesis for hydroponic wheat by about 20% compared to direct light at the same irradiance. Our simulations suggest that high accuracy is not needed in specifying diffuse light fractions in chambers between ~ 0.7 and 1, because simulated photosynthesis for closed canopies plateau in this range. We also examined the effect of leaf angle distribution on canopy photosynthesis under growth chamber conditions, as these distributions determine canopy extinction coefficients for direct and diffuse light. We show that the spherical leaf angle distribution is not suitable for modeling photosynthesis of planophile canopies (e.g., soybean and peanut) in growth chambers. Also, the absorption of the light reflected from the surface below the canopy should generally be included in model simulations, as the corresponding albedo values in the photosynthetically active range may be quite high in growth chambers (e.g., - 0.5). In addition to the modeling implications, our results suggest that diffuse light conditions should be considered when drawing conclusions from experiments in controlled environments.


ABSTRACT.Stabilizing the carbon dioxide–induced component of climate change is an energy problem. Establishment of a course toward such stabilization will require the development within the coming decades of primary energy sources that do not emit carbon dioxide to the atmosphere, in addition to efforts to reduce end-use energy demand. Mid-century primary power requirements that are free of carbon dioxide emissions could be several times what we now derive from fossil fuels (~1013 watts), even with improvements in energy efficiency. Here we survey possible future energy sources, evaluated for their capability to supply massive amounts of carbon emission–free energy and for their potential for large-scale commercialization. Possible candidates for primary energy sources include terrestrial solar and wind energy, solar power satellites, biomass, nuclear fission, nuclear fusion, fission-fusion hybrids, and fossil fuels from which carbon has been sequestered. Non–primary power technologies that could contribute to climate stabilization include efficiency improvements, hydrogen production, storage and transport, superconducting global electric grids, and geoengineering. All of these approaches currently have severe deficiencies that limit their ability to stabilize global climate. We conclude that a broad range of intensive research and development is urgently needed to produce technological options that can allow both climate stabilization and economic development.



  • Volk, T. (2001). The cycling of materials by living systems. In S. Guerzoni, et al. (Eds.), Earth System Science: Proceedings of International School of Earth and Planetary Sciences (pp. 31-38). Universita degli Studi di Siena.

  • Volk, T. (2001). Transformations between life and the global environment. In S. Guerzoni, et al. (Eds.), Earth System Science: Proceedings of International School of Earth and Planetary Sciences (pp. 39-42). Universita degli Studi di Siena.

  • Volk, T. (2000). Forward to the book Writing the Natural Way (by Gabriele Rico). New York: Tarcher/Putnam.

  • Cavazonni, J., T. Volk, B. Bugbee, & T. Dougher, (1999). Phasic temperature control and photoperiod control for soybean using a modified Cropgro model. Life Support and Biosphere Science, 6, 273-278.

ABSTRACT. A modified CROPGRO model is applied to phasic temperature and photoperiod control in order to optimize soybean production for NASA’s program in Advanced Life Support. Baseline model simulations were established using data from soybean temperature experiments conducted at elevated CO2 levels (1100 pmol mol-1) at Utah State University (USU). The model simulations show little advantage in using phasic temperature control alone to increase average seed yield rate over the USU experimental values. However, simulations that combine phasic control of temperature (two phases) and photoperiod (two phases) do indicate the potential to improve seed yield (in g m-2 day -1 ) by approximately 15% over those currently obtained experimentally at USU for soybean cultivar Hoyt. This temperature and photoperiod phasing is experimentally practical. The simulations suggest extending photoperiods over those typically used experimentally during later phases of the crop life cycle, which would lengthen grain fill duration and thereby increase mass per seed. The model simulations indicate that the timing and duration of extended photoperiods would be very important due to possible reductions in seed number m-2. Besides affecting seed yield directly, the model simulations suggest that such reductions may also cause feedback inhibition of photosynthesis due to low seed sink strength at elevated CO2 levels.




ABSTRACT. Spring wheat (Triticum aestivum L., cv. Yecora Rojo) was grown in the intensive agricultural biomc (IAB) of Biosphere 2 during the 1995-1996 winter/spring season. Environmental conditions were characterized by a day/night temperature regime of 27/17o,C, relative humidity (RH) levels around 45%, mean atmospheric CO2 concentration of 450 ppmv, and natural light conditions with mean intensities about half of outside levels. Weekly samples of above-ground plant matter were collected throughout the growing season and phenological events recorded. A computer model, CERES-Wheat, previously tested under both field and controlled conditions, was used to simulate the observed crop growth and to help in data analysis. We found that CERES-Wheat simulated the data collected at Biosphere 2 to within 10% of observed, thus suggesting that wheat growth inside the IAB was comparable to that documented in other environments. The model predicts phenological stages and final dry matter (DM) production within 10% of the observed data. Measured DM production rates, normalized for light absorbed by the crop, suggested photosynthetic efficiencies intermediate between those observed under optimal field conditions and those recorded in NASA-Controlled Ecological Life-Support Systems (CELSS). We suggest that such a difference can be explained primarily in terms of low light levels inside the IAB, with additional effects due to elevated CO2 concentrations and diffuse light fractions.


ABSTRACT. Phasic control refers to the specification of a series of different environmental conditions during a crop’s life cycle with the goal of optimizing some aspect of productivity. Because of the enormous number of possible scenarios phasic control is an ideal situation for modeling to provide guidance prior to experiments. Here we use the Ceres-Wheat model, modified for hydroponic growth chambers, to examine temperature effects. We first establish a baseline by running the model at constant temperatures from 10oC to 30,oC. Grain yield per day peaks at 15oC at a value that is 25% higher than the yield at the commonly used 23oC. We then show results for phasic control limited to a single shift in temperature and, finally, we examine scenarios that allow each of the five phases of the life cycle to have < different temperature. Results indicate that grain yield might be increased by 15-20% over the best yield at constant temperature, primarily from a boosted harvest index, which has the additional advantage of less waste biomass Such gains, if achievable, would help optimize food production for life support systems. Experimental work should first verify the relationship between yield and temperature, and then move to selected scenarios of phasic control based on model predictions.


ABSTRACT. Radiation-use efficiency (dry matter produced per unit absorbed radiation) of a spring wheat (Triticum aestivum L., cv. Veery-10) was 40% higher in controlled growth chamber experiments than under optimal field conditions. Simulations with CERES-Wheat, a field model modified to account for growth chamber conditions, suggest that the observed increase in radiation-use efficiency was due to the large fraction of diffuse light in the experimental chamber. Under optimal conditions in the field, the highest crop growth rates occur when the daily photosynthetic photon flux (PPF) is at its highest levels (50-60 mol m-2 d-1). However, these high growth rates do not appear to be associated with the highest radiation-use efficiency. High PPF levels in the field occur on clear days when the fraction of direct radiation is high and the diffuse fraction is low. In controlled environments with reflective walls, high PPF levels with a large fraction of diffuse radiation can be obtained. Diffuse radiation penetrates to the lower leaves of a canopy better than direct radiation, with the result that the upper leaves are less light saturated and the lower leaves receive more light, increasing radiation-use efficiency, and thus growth rates. The data and model simulations presented here suggest that when diffuse light is a high fraction of the total PPF crop productivity can exceed the highest values attainable in the field under optimal conditions.


ABSTRACT. The CROPGRO crop growth model is adapted in order to analyze experimental data from a soybean (cv. Hoyt) experiment conducted at elevated CO2 levels (1200 pmol mol-1) at Kennedy Space Center, FL. The following adaptations to original CROPGRO produced model agreement with gas-exchange data: the input of square-wave temperature and photosynthetically active radiation (PAR) profiles; the input of the appropriate hydroponic substrate PAR albedo; modified biomass partitioning and developmental parameters; an increased leaf area expansion rate through the fifth vegetative node; a decreased specific leaf area after the fifth vegetative node; and an increased incident diffuse PAR fraction over typical field values. The model demonstrated here suggests that with continued development, modified CROPGRO will be a useful tool in the analysis and eventual optimization of legume production in bioregenerative life support systems.


ABSTRACT. A full assessment of the impacts of land clearance and crop production on atmospheric CO2 requires a systems approach. By considering long-term soil carbon changes and fossil fuel energy inputs, we show that increased crop productivity will alleviate CO2 release to the atmosphere primarily by preventing additional land cultivation. Each hectare of cropland undergoing a simulated threefold crop productivity increase here prevents a net release on the order of 150-200 Mg C to the atmosphere over 100 years by avoiding additional land cultivation which would otherwise be required. This effective carbon sink would slowly diminish with time due to fossil fuel energy input requirements. However, future self-containment of the energy needs of high-yield crop production may displace on the order of 1.0 Pg C per year of fossil fuel carbon, in addition to the carbon sink attributable to avoided land cultivation. By avoiding land cultivation, high yield crop systems also preserve natural ecosystems.


ABSTRACT. Miniaturizing the Earth's biogeochemical cycles to support human life during future space missions is the goal of the NASA research and engineering program in advanced life support. Mission requirements to reduce mass, volume, and power have focused efforts on (l) a maximally simplified agro-ecosystem of humans, food crops, and microbes; and, (2) a design for optimized productivity of food crops with high light levels over long days, with hydroponics, with elevated carbon dioxide and other controlled environmental factors, as well as with genetic selection for desirable crop properties. Mathematical modeling contributes to the goals by establishing trade- offs, by analyzing the growth and development of experimental crops, and by pointing to the possibilities of directed phasic control using modified field crop models to increase the harvest index.


ABSTRACT. Eight circular geologic structures ranging from ~3 to 17 km in diameter, showing evidence of outward-directed radial deformation and intensive brecciation, lie within a linear swath ~15 km wide along a straight line stretching -~700 km across the United States from southern Illinois through Missouri to eastern Kansas. Based on their similar geological characteristics and the presence of diagnostic and/or probable evidence of shock, these structures, once classified as 'cryptovolcanic' or 'cryptoexplosion’ structures, are more confidently ascribed to hypervelocity impact. No other similar occurrence of aligned features is known, and we calculate the probability of a chance alignment to be <10-9 . The unusual alignment suggests that the features are coeval and related to a multiple impact event, with a best-constrained late Mississippian-early Pennsylvanian (~330-310 Myr) age. Calculations suggest that the proposed impact-crater chain is unlikely to have been formed by an incoming impactor disrupted by terrestrial or lunar tidal effects, and may have been the result of a string of asteroidal or cometary objects produced by breakup within the inner Solar System.


ABSTRACT. Use of plants in advanced life support requires models of crop growth to analyze data, to evaluate areas for improvement, and, for design and engineering, to predict the gas exchanges of crops. We used data from experiments at Utah State University and the Kennedy Space Center for wheat (Triticum aestivum L.) and examined it for time dependence of the major three components in the energy cascade: photosynthetic photon absorption, canopy quantum yield, and carbon use efficiency. From the Utah State data, we developed a model with a total of five trends: absorption increasing until canopy closure, then constant; quantum yield as constant, then decreasing during senescence; carbon use as constant. This system probably is the lower limit of simplicity to which a model can be reduced and yet provide substantial utility. We demonstrated this utility by using the model to predict photosynthesis and respiration for experiments at Kennedy Space Center. The most uncertainty arose in predicting a start time for the senescent decrease of canopy quantum yield. The model should be generally applicable to other crops grown in controlled environments, as a generic tool for the design of life support systems.


ABSTRACT. A new growth subroutine was developed for CERES-Wheat, a computer model of wheat (Triticum aestivum) growth and development. The new subroutine simulates canopy photosynthetic response to CO2 concentrations and light levels, and includes the effects of temperature on canopy light-use efficiency. Its performance was compared to the original CERES-Wheat V-2-10 in 30 different cases. Biomass and yield predictions of the two models were well correlated (correlation coefficient r > 0 95). As an application, summer growth of spring wheat was simulated at one site. Modeled crop responses to higher mean temperatures, different amounts of minimum and maximum warming, and doubled CO2 concentrations were compared to observations. The importance of irrigation and nitrogen fertilization in modulating the wheat crop climatic responses were also analyzed. Specifically, in agreement with observations, rain-fed crops were found to be more sensitive to CO2 increases than irrigated ones. On the other hand, low nitrogen applications depressed the ability of the wheat crop to respond positively to CO2 increases. In general, the positive effects of high CO2 on grain yield were found to be almost completely counterbalanced by the negative effects of high temperatures. Depending on how temperature minima and maxima were increased, yield changes averaged across management practices ranged from -4% to 8%.




  • Meleshko, G.I., Shepelev, Ye. Ya., Averner, M. M. & Volk, T. (1994). Biological life support systems. In F. M. Sulzman & A. M Genin (Eds.), Life Support and Habitability, Vol. 2 of Space Biology and Medicine (pp. 357-394). Washington, DC: A/AA.


  • Schwartzman, D.W., Shore, S. N., Volk, T. & McMenamin, M., (1994). Self-organization of the earth's biosphere—geochemical or geophysiological? Origins of Life and Evolution of the Biosphere, 24, 435-450.

  • Volk T. & Keeling, R. (1993). Summary of workshop on interannual variations in the carbon cycle. In M Heimann (Ed.), The Global Carbon Cycle (pp. 579-581). Springer-Verlag.



  • Volk, T. (1993). Cooling in the late Cenozoic. Scientific Correspondence, Nature, 361, 123.

  • Volk, T. (1992). When climate and life finally devolve. News and Views. Nature, 360, 707.


  • Volk, T. & Cullingford, H. (1992). Crop growth and associated life support for a lunar farm. In W. W. Mendell (Ed.), The Second Conference on Lunar Bases and Space Activities of the 21st Century, NASA Publication CP-3166 (pp. 525-530). Washington, DC: NASA.

  • Schwartzman, D. W., & Volk, T. (1992). Biotic enhancement of earth habitability. Encyclopedia of Earth System Science, Academic Press, Volume 1, 387-394.

ABSTRACT. Phenological development affects canopy structure, radiation interception, and dry matter production; most crop simulation models therefore incorporate leaf emergence rate as a basic parameter. A recent study examined leaf emergence rate as a function of temperature and daylength among wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) cultivars. Leaf emergence rate and phyllochron were modeled as functions of temperature alone, daylength alone, and the interaction between temperature and daylength. The resulting equations contained an unwieldy number of constants. Here we simplify by reducing the constants by >70%, and show leaf emergence rate as a single response surface with temperature and daylength. In addition, we incorporate the effect of photosynthetic photon flux into the model. Generic fits for wheat and barley show cultivar differences less than ±5% for wheat and less than ± 10% for barley. Barley is more sensitive to daylength changes than wheat for common environmental values of daylength, which may be related to the difference in sensitivity to daylength between spring and winter cultivars. Differences in leaf emergence rate between cultivars can be incorporated into the model by means of a single, nondimensional factor for each cultivar.


  • Kump, L. R., & Volk, T. (1991). Gaia's garden and BLAG's greenhouse: Global biogeochemical climate regulation. In S. H. Schneider & P. J. Boston (Eds.), Scientists on Gaia (pp. 191-199). Cambridge, MA: MIT Press.

  • Schwartzman, D. W., & Volk, T. (1991). Geophysiology and habitable zones around sun-like stars. In J. Heidman & M. J. Klein (Eds.), Bioastronomy: The Search for Extraterrestrial Life—The Exploration Broadens (pp. 155-162). Springer-Verlag.


ABSTRACT. Assuming steady state of carbon dioxide levels in a "pressure-cooker" atmosphere/ocean system (10-20 bars, near 100oC) produced by a land weathering sink and volcanic source (BLAG model), an abiotic Earth model for 3.8 Ga requires present biotic enhancements of weathering to be on the order of 100 or greater, consistent with the limit inferred from experimental and field studies. Using a plausible ratio of the present biotic enhancement (from higher plants) to enhancements produced by microbial activity alone, along with models for continental growth and outgassing rates consistent with geologic evidence, we find that computed surface temperatures hover near 20°C over geologic time, slowly decreasing to present, after a rapid initial decline as a result of microbial colonization of land. Results are consistent with the first possibility for glaciation in the late Archean/early Proterozoic. Useful modeling of climatic evolution, taking into account biotic enhancement of weathering, can now apparently be extended into the Precambrian, assuming operation of the carbonate-silicate buffer.


  • Caldeira, K., Rampino, M. R. , Volk, T., & J. C. Zachos, J. C. (1990). Biogeochemical modeling at mass extinction boundaries: atmospheric carbon dioxide and ocean alkalinity at the K/T boundary. In E. G. Kauffman & O. H. Walliser (Eds.), Extinction Events in Earth History (pp. 333-345). Berlin: Springer-Verlag.

ABSTRACT. While energetically open, the biosphere is appreciably closed from the standpoint of matter exchange. Matter cycling and recycling is hence a necessary and emergent property of the global-scale system known as Gaia. But how can an aggregate of open- system life forms have evolved and persisted for billions of years within a planetary system that is largely closed to matter influx and outflow? The puzzling nature of a closed yet persistent biosphere draws our attention to the course of evolution of fundamental metabolic strategies and matter-capture techniques. It suggests a facet of the Gala hypothesis, framed in terms of persistence. The oceans, atmosphere, soils and biota constitute a complex system which maintains and adjusts matter cycling and recycling within the constraints of planetary closure such that open-system forms of life can persist. This weaker version of the Gaia hypothesis may be useful because it readily lends itself to at least one form of test. What is the solution to the closed biosphere puzzle, and does it indicate that Gaia merits status as a discrete entity? We suggest several disciplines within the field of biology that might provide tools and perspectives toward reaching a solution. These disciplines include artificial closed ecosystems, prokaryote evolution, the nexus of thermodynamics and evolutionary biology, and hierarchy theory in ecosystem modeling and evolution theory.


  • Bretherton, F. P., Bryan,K. & Woods, J. D. with contributors: J. Hanson, M. Hoffert, X. Jiang, S. Manabe, G. Meehl, S. C. B. Raper, D. Rind, M. Schlesinger, R. Stouffer, T. Volk, & T. M. L. Wigley. (1990). Time-dependent greenhouse-gas induced climate change. In J. T. Houghton, G. J. Jenkins, & J. J. Ephraums (Eds.), Climate Change: The IPCC Scientific Assessment (pp. 173-194). Cambridge, UK: Cambridge University Press.

  • Volk, T., (1990). Shaping nature. The Sciences, 30, 45-50.

  • Volk, T. (1989). Effect of equatorial upwelling on atmospheric CO2 during the 1982-83 El Niño. Global Biogeochemical Cycles, 3, 267-279.

  • Volk, T., & J. D. Rummel, (1989). The case for cellulose production on Mars. The Case For Mars III; Strategies for Exploration - Technical, Vol. 75, American Astronautical Society Science and Technology Series.

ABSTRACT. From examining the consequences of not requiring that all wastes from life support be recycled back to the food plants, we conclude that cellulose production on Mars could be an important input for many non-metabolic material requirements on Mars. The fluxes of carbon in cellulose production would probably exceed those in food production, and therefore settlements on Mars could utilize "cellulose farms" in building a Mars infrastructure.


  • Volk, T., & Bacastow, R. (1989). The changing patterns of ∆pCO2 between ocean and atmosphere. Global Biogeochemical Cycles, 3, 179-189.


  • Volk, T. (1989). Sensitivity of climate and atmospheric CO2 to deep-ocean and shallow-ocean carbonate burial. Nature, 337, 637-640.

  • Volk, T., & Rummel, J. D. (1989). Transpiration during life cycle in controlled wheat growth. Advances in Space Research, 9, No. 8, (8)61-(8)64.

  • Volk, T. (1989). Effect on atmospheric CO2 from seasonal variations in the high latitude ocean. Advances in Space Research, 9, No. 8, (8)153-(8)157.

ABSTRACT. By Late Cretaceous or early Tertiary time, the diversification and proliferation of angiosperm-deciduous ecosystems resulted in higher rates of mineral weathering. This increase in the global average weathering rate would have caused a decrease in atmospheric carbon dioxide and, hence, global cooling. The magnitude of this decrease is quantitatively explored here by developing a formulation for global weathering which combines ecosystems that differ in their fractional global coverage and intrinsic rates of weathering. Incorporating this formulation into models—specifically, several previously developed global steady-state models of the geochemical cycle of carbon between the atmosphere and carbonate rocks—gives results that show significant global cooling from the evolution of the angiosperm-deciduous ecosystems. This cooling may vary from a few degrees up to 10oC. In this way, deciduous ecosystems with high rates of mineral weathering could have contributed to the evolution during the past 100 m.y. of a cooler Earth and thus were a factor in producing conditions that enhanced their global proliferation.


  • Volk, T., & Liu, Z. (1988). Controls on CO2 sources and sinks in the earthscale surface ocean: temperature, nutrients. Global Biogeochemical Cycles, 2, 73-89.

  • Rampino, M. R., & Volk, T. (1988). Mass extinctions, atmospheric sulphur and climatic warming at the K/T boundary. Nature, 332, 63-65.

ABSTRACT. Design decisions to aid the development of future space-based biological life support systems (BLSS) can be made with simulation models. Here we develop the biochemical stoichiometry for 1) protein, carbohydrate, fat, fiber, and lignin production in the edible and inedible p m s of plants; 2) food consumption and production of organic solids in urine, feces,and wash water by the humans;and3)operation of the waste processor. Flux values for all components are derived for a steady-state system with wheat as the sole food source. The large-scale dynamics of a materially-closed (BLSS) computer model is described in a companion paper /I/. An extension of this methodology can explore multi-food systems and more complex biochemical dynamics while maintaining whole-system closure as a focus.


ABSTRACT. The coordination of material flows in Earth’s biosphere is largely made possible by the buffering effect of huge material reservoirs. Without similarly-sized buffers, a bioregenerative life support system (BLSS) for extraterrestrial use will be faced with coordination problems more acute than those in any ecosystem found on earth. A related problem in BLSS design is providing an interface between the various life-support processors. one that will allow for their coordination while still allowing for system expansion. Here we present a modular model of a BLSS that interfaces system processors only with the material storage reservoirs, allowing those reservoirs to act as the principal buffers in the system and thus minimizing difficulties with processor coordination. The modular nature of the model allows independent development of the detailed submodels that exist within the model framework. Using this model. BLSS dynamics were investigated under normal conditions and under various failure modes. Partial and complete failures of various components. such as the waste processor or the plants themselves. drive transient responses in the model system. allowing us t o examine the effectiveness of the system reservoirs as buffers. The results from simulations of this sort will help to determine control strategies and BLSS design requirements. An evolved version of this model could be used as an interactive control aid in a future BLSS.


ABSTRACT. This paper examines several critical uncertainties in long-term carbon cycle modeling: specifically, the dependence of weathering rate on temperature and pCO2, the connection between pCO2 in the atmosphere and in soils, and the effects of a variable terrestrial biosphere on weathering rates. A balance between weathering and metamorphism is used to compare the paleo-CO2 levels and paieotemperatures derived from the weathering systems developed by Berner, Lasaga, and Garrels (1983) and Walker, Hays, and Kasting (1981). The results differ primarily because the latter system explicitly separates the dependence of bicarbonate-ion concentration in river waters on temperature and pCO2. This weathering system has been extended by expressing terrestrial productivity as a function of atmospheric pCO2 in a Michaelis-Menton equation. When the asymptote of maximum productivity is set at 2, 4, and 8 times the present productivity, the global temperature rise from geophysical forcing on the CO2 -greenhouse is lower by about 1o, 2o, and 3oC, respectively, than the temperature rise when productivity is held constant. These calculations delineate the possible scope of the terrestrial biosphere’s capacity to moderate, but not perfectly regulate, climatic changes through its direct effect on soil pCO2.


  • Volk, T. (1987). Limitations on relating ocean surface chlorophyll to productivity. Advances in Space Research, Vol. 7, No. 2, (2)137-(2)140, 1987. (also, reprinted in Modeling in the Global Ocean Flux Study, U.S. GOFS Planning Report Number 4, U.S. GOFS Planning Office, Woods Hole Oceanographic Institution, Woods Hole, Mass., 1987.)

  • Gaffin, S. R., Hoffert, M. I., & Volk, T. (1986). Nonlinear coupling between surface temperature and ocean upwelling as an agent in historical climate variations. Journal of Geophysical Research, 91, 3944-3950.

ABSTRACT. An ocean carbon pump is defined as a process that depletes the ocean surface of ∑CO2 relative to the deep-water ∑CO2. Three pumps are recognized: a carbonate pump, a soft-tissue pump, and a solubility pump. The first two result from the the biological flux of organic and.CaCO3 detritus from the ocean’s surface. The third results from the increased CO2 solubility in downwelling cold water and is demonstrated by a one-dimensional upwelling-diffusion model of an abiotic ocean. In the soft-tissue and solubility pumps, working strengths are defined in terms of the Δ∑CO2 each creates between surface and deep-water. Efficiencies of each pump are quantified as a ratio of working strength to potential maximum strength. Using alkalinity, nitrate, and ∑CO2 to remove the carbonate pump signal from ocean or model data, the individual working strengths of the soft-tissue and solubility pumps can be calculated by scaling the soft-tissue's Δ∑CO2 to the surface-to-deep ΔPO4. This technique is applied to a three-box ocean model known to demonstrate high-latitude control of atmospheric CO2 through a variety of circulation and biological changes. Considering each pump separately reveals that the various changes which lower pCO2 atm in the model are caused primarily by an increased solubility pump. Analysis of global ocean data indicates a positive solubility pump signal, subject to uncertainties in the C:P Redfield ratio and in the preindustrial pCO2 atm. If C:P = 105 and pCO2 atm = 270 µatm, the efficiency of the solubility pump is about 0.5. We suggest that this type of analysis of relative carbon pump strengths will be an effective method for inter-model and intra-model comparison and diagnosis of underlying oceanic mechanisms for pCO2 atm changes.


  • Volk, T. (1985). Majesty of the sphere. The Sciences, vol. 25, 46-50.

  • Volk, T. (1984). Multi-property modeling of the marine biosphere in relation to global carbon and climate cycles, Ph. D. thesis (University Microfilms #84-21570). New York University, New York.

  • Volk, T. (1982). Performance of tornado wind energy conversion systems. Journal of Energy, 6, 348-350.

Book Reviews

A review of The revenge of Gaia: Why the Earth is fighting back — and how we can still save humanity by James Lovelock. Allen Lane, 2006.


A review of Earth system analysis for sustainability by Hans Joachim Schellnhuber, Paul J. Crutzen, William C. Clark, Martin Claussen, and Herman Held (Eds.), MIT Press, 2004.


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