Answer Most likely it would be specific to a field-environmental geologist, or whichever field the person is focusing on. There are degrees in environmental science too... Answer You call them an environmentalist! Answer enviromentalist Answer enviromentalist. In addition it could also be a Geo-scientist as follows: Geoscientists study the composition, structure, and other physical aspects of the Earth. They study the Earth's geologic past and present by using sophisticated instruments to analyze the composition of earth, rock, and water.