Reader is similar, but I wouldn't say equivalent, because only those things working in the Reader can use that environment. For example, when you have project A using project B using project C, you can't define a putStrLn such that project C can use it and be able to override its output stream from project A, while keeping B completely ignorant of that ability of putStrLn or that C even uses putStrLn.

Reader is like a middle-ground between dynamic-scoping and explicit passing of a context argument around as you would in a statically-scoped language.