(part of the "Inclusive History of Conservation GIS" project)
I define Conservation as the struggle for human survival on earth. If you are not in that fight, you are either busy dying out as a dominant species, or you are hoping to get to Mars and live in a plastic bubble.
Back on my planet, Conservation is the activity of protecting earth's fundamental life processes, whose health is critical for humanity's future survival. Those processes evolved in and depend upon intact lands & seas, and a huge variety of other resident species who carry out ecological functions at microscopic to global scales. Conservation is an activity, but it is inextricably bound to and empowered by the social, earth & life sciences.