We must think freshly and clearly about the crucial choices that confront us as a result of the emergence of a radically new relationship between the aggregate power of human civilization and the Earth’s ecological systems, including especially the most vulnerable — the atmosphere and climate balance upon which the continued flourishing of humankind depends.
— Al Gore, The Future

Environment: the set of circumstances or conditions, especially physical conditions, in which a person or community lives, works, develops, etc. The external conditions affecting the life of a plant or animal. (Oxford) Ecology is the study of interactions among organisms and between organisms and their environments. Environmental science is the application of ecology to real-world problems. (Brooker, 1147) The external elements and conditions which surround, influence, and affect the life and development of an organism or population. (MeSH)

Studies have shown that given freedom to choose the setting of their homes or offices, people across cultures gravitate toward an environment that combines three features. They want to be on a height looking down, they prefer open savanna-like terrain with scattered trees and (groups of shrubs), and they want to be close to a body of water, such as a river, lake, or ocean. Even if all these elements are purely aesthetic and not functional, home buyers will pay any affordable price to have such a view. (Wilson, 271-271) Adjective - ‘environmental.’

Biosphere: includes all of the places on the Earth where living organisms exist, encompassing the air, water, and land. (Booker, 5)

Ecosystem: the biotic community of “organisms” in an area as well as the 'abiotic' environment affecting that community. (Brooker, G-11) A functional system which includes the organisms of a natural community together with their environment. (MeSH) Editor’s note - subcomponent of “biosphere.”

Community: an assemblage of populations of different "species."  The types of species that are found in a community are determined by the environment and by the interactions of species with each other. (Brooker, 5) Elements of residence that characterize a population. (MeSH) A set of people with some shared element. The substance of shared element varies widely, from geography to a situation to interest to lives and values. The term is widely used to evoke a sense of collectivity. (NCIt)

Population: a group of organisms of the same species that occupy the same environment. (Brooker, 4) The total number of individuals inhabiting a particular region or area. (MeSH) A group of individuals united by a common factor (e.g., geographic location, ethnicity, disease, age, gender) (NCIt) A complete set of something - people, nonhuman animals, objects, or events. (Hockenbury, A-12)

Ecology: the study of the activities of organisms in their natural environments. A branch of biology. (Brooker, 13) Concerned with the interrelationship of organisms and their environment, especially as manifested by natural cycles and rhythms, community development and structure, interactions between different kinds of organisms, geographic distributions, and population alterations. (MeSH)

Microbiome: the collection of all the “microorganisms” and “viruses” that live in a given environment, including the human body or part of the body, such as the "digestive" system. The human microbiome may play a role in a person’s health. Studying the human microbiome may help prevent and treat disease in the future. (NCI1) A microbiome is all of the "genetic" material found within an individual microbe such as a “bacterium,” fungal cell, or virus. It also may refer to the collection of genetic material found in a community of microbes that live together. (NHGRI)

Migration: periodic movement of human settlement from one geographical location to another. (MeSH) Non-random movement of an object(s) from one location to another. (NCIt) The non-random movement from one place to another of a cell, atom, molecule, etc. (Oxford)

Emigration: the action or an act of leaving a particular place or environment, permanently or temporarily. (Oxford) The process of leaving one's country to establish residence in a foreign country. (MeSH)

Immigration: (migration) into a foreign country to live permanently there. (NCIt) Come to settle as a permanent resident in a different country. (Oxford)

Immigrant: a person who settles as a permanent resident in a different country. Also (especially in Britain), a descendant of such a person.  An animal or plant living or growing in a region to which it has migrated; a cell growing in tissue into which it has moved. (Oxford)