Is one hour of walking per day enough?
Nope. 15 minutes of medium/heavy intensity cardio is the minimum needed to get your heart rate going high enough for it to even count as a cardio workout.
Protip for defining cardio intensity:
>if you can sing the words to a song it's light cardio
>if you can say the words but can't sing them it's heavy cardio
>if you can say the words it's heavy cardio