Environmentalist (noun)

1. A person who advocates for or works to protect the natural environment from destruction or pollution.
2. A person who is concerned about the conservation of the natural world and its resources.

Origin:

From environmental + -ist.

Examples:

1. Al Gore is an environmentalist who has long been an advocate for reducing carbon emissions.
2. David Attenborough is an environmentalist and naturalist known for his documentaries on wildlife and the environment.
3. She's an environmentalist who works with an organization that promotes sustainable living.
4. The environmentalist movement has gained a lot of traction in recent years.
5. Many environmentalists believe that the world needs to take immediate action to address climate change.