International Conference, Novi Sad, Energy – the Source of Existence Biosphere system’s development driven by factors limiting energy flow Kimon Hadjibiros National Technical University of Athens

Introductory notes Energy is used as a concept of Physics Planet Earth is receiving energy from the Sun and emitting energy to space One way transformation of energy (light=>heat) takes place (according to the second law of thermodynamics) and defines a direction for energy systems development

The question Is the development of the Biosphere system driven by factors related to energy? Modeling will be used, based on the ecosystem energy flow model and on the logistic growth model

Necessary definitions-1 Biosphere: the Earth’s ecosystem Energy: a common feature of plants, animals and microorganisms ecological functions Energy flow: amount of energy passing through the ecosystem and supporting metabolism and biomass formation

Necessary definitions-2 Input of energy from the environment to the ecosystem: photosynthesis of plants Output of energy from the ecosystem to the environment: respiration of plants, animals and microorganisms Transfert of energy (trophic chains): plant=>herbivore herbivore=>carnivore carnivore=>carnivore plants or animals=>microorganisms

Ecosystem energy flow model

Impulse All organisms tend to maximize their own biomass, consequently there is a maximization of energy input to every compartment of the Biosphere

Constraint Different factors can potentially limit the energy input to a compartment, but, at every moment, the role of only one factor is decisive The limiting factor is determined by the current conditions

Energy input The driving force for ecosystem development is primary production (production of the plant department) It depends on H (energy input into the plant compartment) It determines the energy regime of the whole ecosystem

Energy limiting factor The factor that limits energy input to the plant compartment determines the whole development of the Biosphere

Logistic growth model Tendency of a system to increase + limiting factor => carrying capacity Replacement of the limiting factor => change of carrying capacity: successive logistic curves A simplistic description that offers a universal final argument

Logistic curve

The development of the Biosphere system A combination of the energy flow model and the logistic growth model (with successive limiting factors and related carrying capacities) can give an interpretation of the development of Biosphere during 4.6 billion years

Pre-History From Big Bang to Solar System and planet Earth: - 15 billion years to – 4.6 b. y. Formation of light nuclei (H-Fe) and of heavy nuclei (Co- U) Life (?) Limiting factors: lack of space-time, lack of chemical elements, high temperature, intense radiation, low probability of life creation

History (general trend) of the Biosphere Formation of planet Earth: billion years First solid continents: b. y. End of meteorite rain, stability: b. y. First methane producing aquatic bacteria: b. y. Photosynthetic bacteria (oxygen production): b. y. High level of aerial oxygen (ozone layer): m. y. Exodus of organisms on land (UV reduction): m. y. Domination of vegetation, fossil fuels: for ~ 500 m. y. Equilibrium of carbon cycle: m. y. Industrial era (increased UV and carbon dioxide: y.

Short-term catastrophes 5 greatest species extinctions in 500 m. y. (about 11 important extinctions) Example: Big impact (- 65 m. y.), suspended solids=>permanent winter, large decrease of energy flow in the Biosphere, mass extinction of species (dinosaurs) Latest mass extinction: from human action

Influence of energy limiting factors Dominant influence of one (at each phase) limiting factor that controls energy flow Possible influence of other limiting factors for short periods

Successive dominant energy limiting factors (for long periods) Primitive life in water, chemosynthesis: no efficient absorption of surrounding energy Photosynthesis: use of abundant light energy, limitation by nutrients in the water and by UV on land Conquest of land: use of light + abundant nutrients, limitation by water (probably) End of growth: limitation by carbon dioxide Our era: increasing carbon dioxide in the air and nutrients in the water, decreasing ozone layer Future limiting factors: nuclear winter, suspended solids, desertification, toxicity, extinctions…, role of technology

A possible answer to the question Energy gives a long term direction to the development of Biosphere Short term strong perturbations alter the general trend

Is the development of the Biosphere system a successful one?