Earth Systems, Planetary Habitability, and Environmental Change

Conditions for a Habitable Planet

• Suitable Temperature: Must allow metabolic processes to function.
• Tectonic Activity: Volcanic eruptions and magmatic intrusions bring essential elements for life to the surface.
• Presence of Liquid Water.
• Radiation Protection: Shielding against high-frequency photochemical radiation (e.g., magnetosphere, ionosphere, ozone layer).

Earth Systems and Human Interactions

System Components

• Nature: Biosphere, Atmosphere, Geosphere, Hydrosphere.
• Society: Population, Lifestyles, Science, Technology, Culture.
• Economy: Agriculture, Industry, Transport, Housing.

Inter-System Exchanges

• Nature to Society (NS): Provides air, water, energy, protection.
• Society to Nature (SN): Generates waste, causes impacts.
• Nature to Economy (NE): Provides resources.
• Economy to Nature (EN): Generates waste, causes impacts.
• Economy to Society (ES): Provides food, shelter, goods, welfare.
• Society to Economy (SE): Provides work, organization.

Environmental Challenges

Historical and Current Crises

• Past Crises: Examples include famines (e.g., millions died of hunger in Europe) and epidemics (e.g., the Bubonic plague killed over a third of Europe's population).
• Current Issues: Overpopulation, urbanization, and other trends associated with the information society.

Environmental Impacts by Sphere

• Atmosphere: Global warming.
• Hydrosphere: Droughts, reduction of glaciers and water bodies.
• Geosphere: Resource depletion, erosion.
• Biosphere: Deforestation, loss of biodiversity.

Societal Structures and Theories

Service Societies

Societies where the majority of the active population works in sectors like health, education, hospitality, etc. This often occurs when agricultural and industrial production becomes highly technified (requiring less labor) or when these productive sectors are relocated to other countries.

Systems Theory Application

Systems Theory is a study method aiming for a closer understanding of complex systems using new technologies, supercomputers, simulation programs, etc. Understanding how complex natural systems work and their relationship with social systems helps solve problems arising from the complex interactions between humanity and nature.

Gaia Theory

Proposed by James Lovelock, this theory interprets Earth as a complex interrelationship between environmental systems, forming a self-regulating superorganism.

Atmospheric Processes and Climate

Solar Radiation Effects

• Light Radiation: Affects perception of colors and the photosynthetic activity of plants.
• Infrared Radiation (Heat): Reflected or emitted by the Earth, it generates horizontal air mass movement, which tends to equalize temperatures between various parts of the planet.
• Why is the Sky Blue? This phenomenon is caused by the scattering of light in the atmosphere. The way light scatters depends on the location and type of particles present, influencing colors and temperature variations.

The Greenhouse Effect

This refers to the warming of the atmosphere due to the presence of various gases, called greenhouse gases, which trap heat by absorbing and re-emitting infrared radiation.

Principal Greenhouse Gases:

• Water vapor (H₂O)
• Carbon dioxide (CO₂)
• Methane (CH₄)
• Nitrous oxide (N₂O)

Benefit: The natural greenhouse effect maintains an adequate temperature on the planet to host living organisms.

Causes of Climate Variations

Natural Causes

• Sudden: Volcanic eruptions.
• Short-term: Solar cycles (e.g., sunspots).
• Medium-term: Changes in Earth's orbital geometry (Milankovitch cycles).
• Long-term: Tectonic movements.

Anthropogenic Causes

• Addition of atmospheric greenhouse gases (e.g., CO₂, CH₄, N₂O) and aerosols from human activities.
• Landscape destruction and modification (e.g., deforestation, urbanization).
• Steady accumulation of excess CO₂.
• Emission of particles that destroy the ozone layer (Note: Ozone depletion is a separate issue from the greenhouse effect, though often linked through industrial emissions).