Final answer:
Anthropologists join the Human Terrain System due to their interest in the interdependence of humans and nature, as well as their fieldwork skills.
Step-by-step explanation:
Anthropologists join the Human Terrain System for various reasons. One reason is their deep-seated interest in the interdependence of humans and nature. Anthropologists are concerned with how people interact with their environments and the impact of unsustainable modes of subsistence on the environment. Additionally, anthropologists are trained to work in the field and have the skills to adapt to different situations, making them valuable contributors to a global community.