Learn Hardcore Japanese: sairiyou wo suru to, sigen wo mamoreru. - If we reuse things, we can protect resources.

再利用 is originally a noun (“reutilization/reuse”). Adding を + する turns it into a verb phrase meaning “to do reuse.” However, modern Japanese also allows you to combine the noun and する directly as 再利用する, which is perfectly natural and slightly more concise.

What kind of conditional is the と in 再利用をすると? How does it differ from other conditionals like たら or なら?

The と here is the plain (resultative) conditional, which expresses a general truth or automatic consequence: “Whenever/If you reuse, you (naturally) can protect resources.”

たら often implies a one-time or past condition (“if/when once that happens…”).
なら sets a topic or supposition (“if it’s the case that…”).
と stresses that B regularly or inevitably follows A.

What does 守れる mean? How is it formed from 守る?

守れる is the potential form of 守る (“to protect/defend”), meaning “can protect.” To form the potential of a group 1 verb like 守る, you change the final -u to -eru, so 守る → 守れる. It shows ability or possibility.

Could we express the same idea as 資源を守ることができる? How does that compare to 守れる?

Yes. 資源を守ることができる literally means “it is possible to protect resources.” It’s more formal and wordy. 守れる is shorter and more colloquial but equally correct. Both convey ability.

Why is there no subject in this sentence? Who is doing the reusing?

Japanese often omits the subject when context makes it clear. Here it’s understood that “people,” “we,” or “you” in general perform the action. In English we might add “you” or “we,” but in Japanese it’s natural to leave it out.

Is 再利用 the same as リサイクル?

They overlap but differ subtly:

再利用 (“reuse”) means using an item again for the same or a new purpose without major processing (e.g. using a glass jar as storage).
リサイクル (“recycle”) implies breaking down or processing materials to make something new (e.g. melting plastic to form new bottles).

Why does 資源を守れる use を again? Isn’t 資源 the topic?

Here, 資源 is the direct object of the verb 守れる, so it takes を. If you made it the topic, you might say 資源は守れる, which shifts the nuance to contrast or emphasis (“As for resources, [they] can be protected”).

The sentence is in plain form. Is this level of politeness okay in written instructions or signage?

Yes. Public notices, slogans, and instructional signs often use plain-form statements to sound concise and universally applicable. In conversation or formal writing, you might choose the polite form (再利用をすると資源を守れます).