Could be a stupid question.

I want to change maps on ARK, but don't want to lose progress on The Island, Is it possible to download a backup of the island and restore it later on?

Check the backup tab, for the easiest way. Otherwise, you'll need to FTP to your server, and manually backup the files.

Note: You will not be able to restore your settings / ini files via a manual FTP backup, and through the automatic backup process, you're presently not able to restore any Expert settings. (I recommend making a txt document for each of your expert settings files, if you use the automatic backup process.)