All living things depend on Earth’s cycles to provide them with what they need to survive. These cycles produce oxygen, water and important nutrients that keep them alive. Each step in these cycles is interconnected, so if one part of the process is changed by human activity, they whole cycle is affected.

By understanding how these cycles work, we can better understand how our actions affect the environment and how we can better protect Earth and its inhabitants.

The movement of energy into and out of the Earth System differs from the other cycles which continually circulate throughout the four spheres. Energy works more like a scale with both sides balanced. One side should equal the other side. The amount of energy entering the system should equal the amount removed.

If the planet were to take on more energy than it released, the climate would become warmer. If it lost more energy than it gained, the climate would become cooler. Because of the balance-scale nature of Earth’s energy cycle, geographers refer to is Earth’s energy budget.

There are three main sources into the Earth’s energy budget:

Most energy ( %) is solar energy. Solar energy drives the winds, ocean currents, caused weathering, soil formation.

There are three main sources into the Earth’s energy budget: Geothermal energy accounts for percent of the budget. Geothermal is created from within and drives the movement of crustal plates, powers volcanoes and earthquakes.

There are three main sources into the Earth’s energy budget: Tidal energy (0.002 percent) results from the Moon’s pull on Earth’s oceans. Although small comparatively, it is powerful enough to slow down the Earth’s rotation.

About 30 percent of the incoming energy is reflected back into space without being changed. (Scatter, clouds, ground). So what happens to the remaining energy that enters the Earth system?

The remainder of the energy is used within the Earth system. It might bring about evaporation and precipitation in the water cycle, changed to wind and wave energy, or simply be converted to heat and radiated back into space.

Some of the energy is stored in water and ice, in plants and in sedimentary rocks.

As energy moves through the Earth System it changes. With every change, a bit is transferred to heat and ultimately lost to the cycle. According to a basic principle of physics, energy can never be completely recycled. This degradation of energy is an important difference between the energy cycle and the carbon and water cycles.

THE LAWS OF THERMODYNAMICS Thermodynamics deals with the conversion of heat energy into other forms of energy within a closed system. The laws of thermodynamics deal with the ways in which energy flows.

THE LAWS OF THERMODYNAMICS The first law states that energy cannot be created or destroyed, only changed from one form to another. e.g. Solar energy can be stored in plants, which die and eventually become fossil fuels. Fossil fuels can be burned at an electric power plant to generate electricity which then powers a lightbulb.

THE LAWS OF THERMODYNAMICS The second law states that when energy is converted it goes from a more concentrated useful form to a generally less useful and less concentrated form. Some energy will always be lost, usually as heat. From the previous example, the light bulb, while producing light energy will invariably give off heat which is ultimately lost.

EFFECTS OF THE EARTH’S SURFACE The Earth’s surface is not uniform (oceans, deserts, grasslands, glaciers, cities). These different areas of the Earth’s surface reflect solar energy at various rates. The percentage of energy that is reflected without being changed is called the albedo.

EFFECTS OF THE EARTH’S SURFACE For example: The albedo of a forest would be between 5 and 10 percent. A field of freshly fallen snow would reflect between 80 and 90 percent. Desert areas reflect around 35 percent of solar energy.

EFFECTS OF THE EARTH’S SURFACE While the albedo changes from surface to surface, the planets overall albedo is roughly 30 percent. An area’s albedo will change when the amount of energy absorbed or reflected changes. Examples?

EFFECTS OF THE EARTH’S SURFACE Examples? Russell in the winter versus summer.

EFFECTS OF THE EARTH’S SURFACE Examples? Forested area cut down for housing development.

EFFECTS OF THE EARTH’S SURFACE The alterations in the energy cycle brought about by transformation of the landscape are further examples of how each part of the Earth System affects other parts.

ENERGY FLOW IN ECOSYSTEMS All energy used by living things comes from the Sun and passed along the food chain to carnivores. The process is not very efficient as a great deal of energy lost at each trophic (feeding) level to respiration.

ENERGY FLOW IN ECOSYSTEMS While energy from the Sun fuels all living things, less than percent of solar energy is actually captured by living things. Through photosynthesis, the producers store energy in the food they make. Some is used for life processes, then store the rest.

ENERGY FLOW IN ECOSYSTEMS Herbivores get energy by eating the producers and carnivores get energy from eating herbivores and other carnivores. Thus energy is passed along the food chains from producer to carnivore.

ENERGY FLOW IN ECOSYSTEMS Depending on the types of species and ecosystem involved the energy lost will vary. This energy cannot be recaptured by any of the organisms in the food chain – it is lost forever. Thus energy flow is a one-way process along the food chain.

Total Energy Flow in Kilojoules per Square Metre of Land per Year If total energy of the producers represents 100 percent of the food chain, calculate the percentage of energy that is lost each step.

ENERGY FLOW IN ECOSYSTEMS The energy lost in moving to successive trophic levels explains why most food chains and webs rarely have more than four consecutive links of energy transfers.

ENERGY FLOW IN ECOSYSTEMS Energy flow also demonstrates why the eating habits of people can influence how many humans planet Earth can support. How can this be?