Because of the multidisciplinary and interdisciplinary nature of environmental education, it is often difficult to define. The global ramifications of individual or collective action on the rest of the world have only recently become concerns for society. Historic views of air and water were that the abundance and vastness of these resources allowed for unlimited use and abuse. Today, additional chemical burdens on the environment and alterations of the natural systems have increased. This has been coupled with an increased understanding of the effects of human action on the environment, including long term effects.
Every human action has an impact on the environment, both immediately and globally.
For example, an elementary mathematics class might calculate the amount of solid waste that 30 students produce in a year, or the issue of airborne toxins can be used when studying about prevailing winds in an earth science class. Case studies provide the educator with flexibility and control as the teacher becomes the curriculum designer. The class, directed by the teacher, analyzes a particular issue, developing focused information and skills. A class might choose the global issue of loss of biodiversity focusing their study on the changes in their own neighborhood which have caused a loss of species. Insertion, the addition of specific courses in environmental education, tends to be used more at the high school level.