Control Processes in Ecological Systems

Life is based on biochemical reactions that convert inorganic substances stored in the environment into organic ones and back. The existing power of the biochemical fluxes of synthesis and decomposition of organic substances is such that, were not these feedback processes rigidly correlated, the environment could change completely in time periods of several tens of years, reaching a state where life would be impossible.

For example, the global amount of atmospheric CO2 is of the order of M——103GtC (1 Gt = 109t). The mean global rates of biochemical synthesis P+ and decomposition P— are of the order of P+ — P- — 102Gt C yr-1. If the rates of synthesis and decomposition were not correlated, that is, if they coincided by the order of magnitude only, their relative difference would be of the order of unity, |P+ - P- |/P± - 1. In such a case, if synthesis exceeded decomposition, P+ > P—, the global biota would use up the entire store of atmospheric carbon on a timescale of M-/P- — 10 years. This would render further photosynthesis and existence of life impossible. The amount of organic carbon in the biosphere (living biomass, humus, and oceanic dissolved organic carbon) is of the same order of magnitude, M+ — 103 GtC. If the rate of decomposition exceeded the rate of synthesis, the global biota would be able to destroy itself completely in equally short periods of time.

The fluxes of synthesis and decomposition cannot be correlated with each other directly. Synthesis and decomposition of organic matter represent independent biochemical processes that are generally performed by different species under different environmental conditions (temperature, humidity, etc.). While primary productivity is limited by the incoming solar radiation, there are no physical limitations on the rate of decomposition, since the latter is ultimately dictated by the population numbers of heterotrophic organisms. Characteristic ecosystem values of P+ and P— are determined by the individual design of every species, population abundance, and overall numbers of auto-trophic and heterotrophic species inhabiting Earth. The values of P+ and P— cannot coincide with an infinite precision a priori.

For example, even if the mean global rates of synthesis and decomposition coincided, say, with a high accuracy of 1%, a x |P+ - P- |/P+ — 0.01, such a biota would completely destroy its environment (or self-destroy) in M±/\P+ - P- | = M±/(aP+) - 103 years, that is, nearly instantaneously on a geological scale. The life span of the biota is short for any realistic accuracy of the coincidence of P+ and P—. To extend the biotic life span to the documented several billion years of life existence, T — 109 years, one has to demand that the living organisms and their ecological communities are designed such that the mean rates of synthesis and decomposition performed by them coincide to the accuracy of M±/(P+T) — 10-8, which is improbable.

Correlation of the ecological fluxes of synthesis and decomposition of the organic matter is achieved indirectly, via continuous sensing of information about the current state of the environment that is performed by living organisms. The biota reacts to any environmental change as soon as its relative magnitude reaches some critical value, biotic sensitivity £b. As long as the magnitude of the environmental change remains lower than biotic sensitivity, synthesis and decomposition of organic matter by the biota may proceed in a noncorrelated manner at different rates. As soon as some environmental parameter changes by £b, the biota initiates compensating negative feedback processes and keeps them going until the disturbance is diminished to a level below £b, when the biota no longer notices it. The optimal state to which the ecosystem ultimately returns (the state of ecological homeostasis) is thus defined to an accuracy of £b. For example, if the amount of inorganic carbon in the atmosphere changes by £b — 1% (e.g., increases), the biota can enhance the rate of biochemical synthesis (that takes away CO2 from the atmosphere) or reduce the rate of biochemical decomposition (that would further add to the atmospheric CO2 amount) until the perturbed concentration relaxes to its optimal value. The same principle can be used to control temperature, humidity, and all other environmental parameters.

The huge information fluxes processed by the natural biota (Figure 2c) are necessary for sensing the environment, reading the data about its state, and ensuring regulatory ecological processes aimed at compensation of possible environmental disturbances. This biotic regulation of the environment is equivalent to an operating system where the characteristic rate of information processing exceeds the maximum possible rate of automatic control provided by all computers of the modern civilization by 20 orders of magnitude. Biotic regulation is based on genetic programs ofbiological species ofthe biosphere. It can be viewed as an automatically controlled operating system where the program of automatic control has been tested for reliability in an experiment lasting for several billion of years (during the whole period of life existence).

The relative degree of unsteadiness in the work of a computer is defined as the ratio of the rate of human-induced changes in the computer program to the total flux of information processed by the computer. The relative unsteadiness of the regulatory program of the natural biota is fantastically low, 1 bit s" _1/1035 bits_1 = 10-35. (Rate of program change corresponds to the rate of information change in the course of evolution, 1 bit s~ . The total information flux processed by the natural biota is equal to 1035bits~\) It means that each working regulatory program is maintained by the natural biota in a steady state for the maximum possible periods of time.

Genetic information of the natural biota changes completely every 3 x 108 years. Thus, during the whole period of life existence (3.8 x 109 years) there were no more than 12 completely different programs of biotic regulation of the environment. A working program of biotic regulation is presumably unique for each particular epoch. Evolution of the biotic regulatory program is possible due to acting geophysical and cosmic processes; that is, directional changes in parameters that cannot in principle be controlled by biota (e.g., solar activity) may lead to a situation when the old regulatory program is no longer the most effective one. As a result, there opens a possibility for a new more effective regulatory program of the biota to establish in the result of genetic modifications (i.e., appearance of new species) in the old program. New regulatory programs appearing in the course of evolution are exposed to a thorough experimental testing.

The humankind is unable to create a technological system equivalent to the natural biota, where each micron of the Earth's surface is controlled by dozens of independently functioning unicellular and multicellular organisms, each living cell processing an information flux similar to that of a modern PC. The genetic program of the natural biota cannot be substituted by any technological program of automatic control (even if this technological program is characterized by fluxes of energy and information similar to those in the natural biota), because search for appropriate technological decisions and their testing is performed by human beings and can take billions of years. Technological solutions of ecological problems can be only successful on a local scale. Globally, the only promising strategy for the modern humankind is therefore strategy of preservation of the remaining natural biota and gradual restoration of its global regulatory potential.

See also: Biological Integrity; Boltzman Learning; Ecological Network Analysis, Ascendency; Energy Flows in The Biosphere; Systems Ecology.

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