An Overview of the Model

This chapter examines the Human Ecosystem Model (HEM), which began as a seedling in the late 1960s and has grown and developed into a middle-aged forest today. Human ecosystem is defined as a coherent system of biophysical and social factors capable of adaptation and sustainability over time. Coherence is relative and varying within human ecosystems. There can be “tight coherence” between available energy flows and economic activity, as when a scarcity of petroleum reduces industrial production and raises costs. There can also be “loose coherence,” such as the relationship between available water supplies and the performance of educational institutions. The chapter also elaborates on some of the other key words from the given definition of human ecosystem, such as capability, adaptation, and sustainability.