If you volunteered last year you do not fill in a whole application again. The organization sends a renewal link instead.
The renewal form
It is short. Your name, your email and the details they already hold are filled in — you are confirming them, not typing them again. What is actually asked is what could have changed: are you still available, do you still want the same crew, has anything expired.
The link is yours and works once. Do not forward it to a friend who wants to volunteer; send them the organization's application form instead, which is a different thing and asks all the questions.
After you send it
You are moved into the new season and told. Whatever the organization records about you — hours from past years, qualifications, the crews you have worked — comes with you. Seasons are how the history stays separate without being lost.
You did not get a renewal link
Either the organization has not sent them yet, or your last season is far enough back that they are treating you as a new applicant again. Ask them. If they have moved on and want a fresh application, that is their call, and everything you did before is still on your record.
You do not want to come back
Ignore the email, and the reminders stop when the season closes. If you would rather hear nothing at all, use the unsubscribe link at the bottom of any message they send you — see Your information for what that does and does not cover.