A person who holds a theory about population, especially one that opposes Malthusianism; (also) a person who considers population to be a significant element in determining the power of a state.
Origin
Early 19th century. From population + -ist.
Definition of populationist in US English:
populationist
nounˌpɒpjʊˈleɪʃ(ə)nɪst
A person who holds a theory about population, especially one that opposes Malthusianism; (also) a person who considers population to be a significant element in determining the power of a state.