This chapter explores the ecological history of the Ridge, including its human ecology. Delhi has witnessed many waves of migration, and this is largely due to the city's micro- and macrohabitats; the Ridge serves as an ecological divide between the arid lands to the west and the fertile ones to the east. Many human and non-human migrants have crossed this crucial threshold, leading to a dynamic, ever-changing set of ecosystems on the Ridge.
Below is an outline of the chapter sections, along with the time periods and places covered in this chapter. (N.B. Some shifting and reorganization occurred between the production of this image and the final publication of the book.)