For most of ecology's history as a discipline, the focus of study was on pristine, wildland sites. Urban areas were seen as human-disturbed places less worthy of investigation. Urban ecology experienced a paradigm shift in the latter part of the 20th century, when it began to focus on the structure and function of cities as ecosystems. The establishment of two long-term ecological research sites in the Phoenix and Baltimore metropolitan areas in 1997 lent credibility to the study of urban ecosystems.
CAP LTER has been a leader in a burgeoning understanding of urban socio-ecological systems, and by extension, the broad integration of social science into ecological studies. In the process, CAP has led a transformation of education and graduate training that truly integrates disparate disciplines with an emphasis on problem-solving in cities. This transformation has extended to K-12 education through an award-winning program called Ecology Explorers.