#environmentalsystems

This article looks at how El Paso are dealing with drought, and this would make a great comparison with the two main drought case studies: East Africa and Australia.

This issue in particular links many areas of geography such as disparities in wealth and development and water resources. 

This article looks at why water aid is decreasing despite global increases in aid. 

This links to a video that details the issue of water scarcity in Las Vegas, Nevada, USA. 

This will be useful for both Environmental Systems and Geography Water Resources options (Water and Change in Geography Core).

A month ago today was World Water Day, and this article looks into how far we have come in reaching global water sanitation goals. 

Equilibrium: the tendency of the system to return to an original state following disturbance. At equilibrium a state of balance exists among the components of that system.

There are four different types of equilibria:

Steady-state equilibrium

Characteristic of open systems where there are inputs and outputs of energy and matter.

Despite inputs and outputs, the system as a whole remains more or less constant in state. Example: a climax ecosystem.

There are no long term changes with this type of equilibria, but there may be small fluctuations in the short term e.g. in response to weather changes.

 The system will then return to its previous state following the removal of the disturbance.

Some systems may experience long term changes in equilibrium, whilst still maintaining the integrity of the system, e.g. succession.

Static equilibrium

There is no change over time.

When static equilibrium is disturbed, it will adopt a new equilibrium.

Most non-living systems, e.g. a pile of rocks, are in static equilibrium because they do not change their position or state.

Static equilibrium CANNOT occur in living systems because life involves exchange of energy and matter with the environment.

Stable and unstable equilibria

In stable equilibrium the system tends to return to the same equilibrium after a disturbance.

In an unstable equilibrium the system returns to anewequilibrium after disturbance.

Possible example for unstable: climate change, where the new state of equilibrium for the climate may be hotter than previously.

Definitions:

Open system(s):A system that exchanges matter and energy with its surroundings

Climax ecosystem: An ecosystem with a stable developed community known as a climax community.

Succession:The process where one community is replaced by another. It is a natural increase in the complexity of the structure and species composition of a community over time.

This is part of the systems section of the Environmental Systems course.

These two laws can sound a little complicated, but they're actually pretty simple.

Law 1:

ENERGY IS NEITHER CREATED NOR DESTROYED

i.e. the total energy in any isolated system  (see below for definition) is constant. Only the form that the energy takes can change.

Example: Light energy enters a system from the sun, where it is converted to stored chemical energy (glucose). Chemical energy is then passed along as food. No new energy has been created, it is just passed along the food chain.

Law 2:

THE ENTROPY OF AN ISOLATED SYSTEM NOT IN EQUILIBRIUM WILL TEND TO INCREASE OVER TIME.

i.e. energy conversions in systems are never 100% efficient. When energy is transformed into work, some energy is always lost to the environment as waste heat. Therefore, at each trophic level there is a reduction in the amount of energy passed on.

Word equation for Law 2: energy=work+heat (and other wasted energy)

Definitions

Isolated system: exchanges neither energy nor matter with its environment. The universe is thought to be the only natural isolated system. All other natural systems are either open (majority) or closed systems (rare).

Entropy: Refers to the spreading out or dispersal of energy

Equilibrium: A state of rest or balance. There are four kinds: stable, unstable, static and steady-state (see equilibria post for more information).