How to preserve iphone contacts

Hi

I've only recently started using icloud to keep my macs and iphone in sync. So far it seems to work well but I have one worry. What happens if I mistakenly delete a contact on the phone or worse still someone else gets their hands on it and deletes the lot! I believe this would result in syncing over all my devices and the deletion of all records of contacts I have.

Can someone please explain to me the best way to avoid this situation?

Thanks