Introduction

As a verbal descriptor, theoretical concept, and natural unit of biological organization, “habitat” has a long history in ecology. Use of the term dates back over 250 years to Linnaeus. However, the modern concept of habitat was slow to emerge. Starting in the early twentieth century, it became relatively common to use “habitat” as a descriptor for the vegetation and other environmental conditions where a species is found. Eventually, habitat came to be defined in a more multi-faceted way as the physical structure of the place where a species exists as well as the resources provided at the location. More so than any other ecologists, Joseph Grinnell and Victor Shelford are to be given the most credit in bringing about our modern concept and definition of habitat. In the 1920s, Georgy Gause conducted what was probably the first quantitative study of habitat; he examined the habitat associations of 15 grasshopper species. In the 1930s, through the writings of Aldo Leopold, wildlife ecology emerged as an academic discipline distinct from ecology. In studying habitat, wildlife ecologists were also attempting to determine the habitat requirements of a species. This was another important step forward; recognition that daily survival of individuals and maintenance of the population and species came about to the extent that necessary habitat conditions and resources were met. Although there is currently some debate about the exact definition of habitat and related terms, the modern concept of habitat is widely accepted.