environmentalist
noun/ɪnˌvaɪərnˈmɛntlɪst; ɪnˌvaɪrənˈmɛntlɪst/ 
a person who is concerned about the natural environment and wants to improve and protect it
environmentalism/ɪnˌvaɪərnˈmɛntlˌɪzəm/
/ɪnˌvaɪrənˈmɛntlˌɪzəm/
noun [uncountable]
Definition of environmentalist noun from the Oxford Advanced American Dictionary
