Here's a breakdown of the terms:

* Environmental Scientist: This is a broad term that encompasses a wide range of fields, including environmental chemistry, environmental toxicology, environmental engineering, and environmental policy. They study the interactions between humans and the natural world, and work to protect and manage the environment.

* Ecologist: This term is more specific and focuses on the study of ecosystems, how organisms interact with their environment, and how these relationships change over time.

Other terms you might encounter include:

* Environmentalist: This refers to someone who advocates for the protection of the environment, often through activism or advocacy. They may not necessarily be scientists, but they are passionate about environmental issues.

* Conservationist: Someone who works to protect and manage natural resources, often focusing on specific species or habitats.

The best term to use depends on the specific context. If you're talking about someone who researches the environment scientifically, "environmental scientist" or "ecologist" are the most accurate choices.