Question

Don't use plastic bags to save the environment.
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What is the meaning of 'save' here?
what other words can we use instead of 'save'?

Answer 1

I would use the synonym of "conserve."

Answer 2

Your sentence is misleading.

It would be better to say,

To save the environment, don't use plastic bags.

or

Don't use plastic bags; they hurt the environment.

or

To conserve the environment, don't use plastic bags.