Like language as instinct or organ or behaviour or calculus or tool, language as ecology (Haeckel's term coined in 1866) is a metaphor. It is originally coined by C.F. Voegelin, F.M. Voegelin & Noel Schutz (1967) on The Language Situation in Arizona as Part of The Southwest Culture Area (acknowledged by Haugen). In his seminal paper, The Ecology of Language, Einar Haugen (1972: 325) defines the relationship between language and ecology as “the study of interactions between any given language and its environment,” in which “environment of a language is the society that uses a language as one of its codes” (ibid.). With a passage of time, the concept of 'ecology' within lingusitics broadened including environmental degradation as a linguistic concern (Halliday 1992). Since then the various approaches in the study of language with ecology came to be known as ecolinguistics. In due course of time, this approach has gained its significance in the wake of language endangerment and diminishing linguistic diversity. This is further reinforced by a belief that linguistics can address the contemporary problems by translating it into terms which our tools especially equip us to address (Dasgupta 1999).
Unlike other approaches in linguistics, the ecological approach stresses the 'whole' rather than the 'parts', and studies the interrelation of phenomena of reality and of the key nature of these interdependencies inside the ecosystem in which the languages exist. In other words, ecolinguistics is primarily concerned with the relations between language varieties and their geographical, demographic, social and political contexts. An ethical value that ecolinguistcs bears in mind -- people involved and their autonomy, and people must be its centre and its main reason for existing.
Language as a species, again drawing as a metaphor, is a parasite – its life and vitality depend on it's hosts i.e. speakers, domains, on the society they form, and on the culture in which they live. It is a known fact that the evolution of human languages and verbal behaviours coevolve in conjunction with demographic, socioeconomic, political, and technological events in their milieus. The linguistic objects are also controlled by the sociocultural experiences of their speakers, and the linguistic systems are affected by the socioeconomic and politicocultural conditions of individuals, who are able to decide personally on the language to be transmitted to their successors. Therefore, languages exist in an environment that are either friendly, or hostile or indifferent with respect to a language. In term's of language endangerment, a language can be healthy or endangered or moribund or even folkorised.