1) Ecologist 
Preservationist is generally understood to mean historic preservationist: one who advocates to preserve architecturally or historically significant buildings, structures, objects or sites from demolition or degradation. Historic preservation usually refers to the preservation of the built environment, not to preservation of, for instance, primeval...
someone who advocates the protection of a natural environment with minimal human intervention
noun someone who advocates the preservation of historical sites or endangered species or natural areas
a person who advocates or promotes preservation, esp. of wildlife, natural areas, or historical places.