closed system
a system that has little or no links to its external environment.

cumulative change
a type of global change resulting from individual local activities that do not directly affect a global functioning system but when widely replicated in multiple locations are globally significant.

driving forces
societal forces that bring about global environmental change, including population, economy, technology, ideology, and social organizations.

ecosystem
self-regulating natural community of plants and animals interacting with one another and with their non-living environment.

entropy
a measure of the amount of energy in a system that cannot be used to perform work; high entropy means that the energy in the system has very little capacity to do work.

greenhouse effect
the role of various trace components of the atmosphere (such as H₂O, CO₂, etc.) in reabsorbing certain wavelengths of the energy spectrum radiated from the earth’s surface thereby increasing the global temperature. This effect occurs naturally, but is augmented by human activities such as the burning of fossil fuels and land cover changes since these changes emit trace gases that become further concentrated in the atmosphere (enhanced greenhouse effect).

greenhouse gases
a group of gases, including carbon dioxide, methane, chlorofluorocarbons, ozone, and nitrous oxide that are radiatively active, i.e., they absorb longwave radiation in the atmosphere.

Industrial Revolution
a series of social, political, and economic changes within the British economy between 1750 and 1850 that transformed the forces of production; the influences of these changes spread throughout parts of the world and were seen in the US with the growth of the steel industry, engineering, and increased electricity consumption.

nonrenewable resource
a resource that is available in fixed amounts on the earth and can be totally depleted because (1) it is not replenished by natural processes or (2) it is used more quickly than it can be replenished.

open system
a system that has flows to or links with its environment.

paradigm
the working assumptions, procedures, and findings routinely accepted and employed by a group of people; a paradigm defines one’s view of the world and the approach one takes to defining problems, researching them, and solving them.

sinks
places where materials are collected or disposed of either temporarily or permanently (i.e., the global atmosphere is a sink for greenhouse gases; biomass or riverbeds are temporary sinks for carbon, nitrogen, and phosphorous.)

sustainable (-ability)
an activity that can be maintained without jeopardizing the health of humans or the environment now or in the future.

sustainable development
development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

system
a group of elements organized in such a way that every element is to some degree dependent on every other element.

systemic change
a type of global change that results from human activities that directly affect a globally functioning system (e.g., release of greenhouse gases into the atmosphere may lead to changes in the global climate system)

technology
practical methods for controlling physical objects and forces; the means by which humans modify the material nature of their world.

Type I ecology
a system characterized by a linear flow of material throughputs; involves the consumption of unlimited resources and the production of unlimited wastes.

Type II ecology
a system characterized by a quasicyclic flow of material throughputs; involves the consumption of energy and limited resources and the production of limited wastes.

Type III ecology
a system characterized by a cyclic flow of materials that are continuously recycled among the members of the system; in an ideal state, involves minimal exchanges with the environment, except for energy inputs.