If you booked it as a single trip, usually you have to be on the first flight to be allowed onto the connection flight, but since the airline is cancelling the first flight, I would give the airline a call to see what the circumstances are regarding this.
Usually, airlines give you the option of booking a ticket with a cancellation option. This might be a wise idea for your backup flight, to pay the little bit extra, so if your original flights opens up again, you will get most of your money back.
