Question

what arguments might a conservationist use to justify president Roosevelt's expansion of the power of the federal government

Answer 1

The department was a way to control big businesses & avoid corruption so that the public wouldn't be harmed.

Answer 2

A conservationist might justify President Roosevelt's expansion of the power of the federal government by arguing that increased federal power could protect land and endangered animals. Roosevelt signed laws establishing five national parks, and broadened executive power by signing the Antiques Act in 1906.
Hope this helped!
@Below you may have answered the wrong question XD