There are two Campaign Modes - the first - this one - is the story mode, in which the story for the game is told. You play through a series of eight missions that, collectively tell the plot and sub-plots that make up the main story mode of the game.
These consist of:
BEFORE YOU BEGIN
Perhaps the most important thing you need to remember about the game is that the structure of play has you rotate between the islands, but the progress you make is retained. What that means is that when you rotate back to the island every other Mission, you are faced with that island in whatever the condition was when you left it in the mission before the last!
That should encourage you to play conservatively and to always strive to leave the island in as good condition as you can because it has a direct impact on the next Mission...
More to the point, success in later missions is entirely dependent upon your success in the PREVIOUS missions. So if things went bad you may just find that starting the game over completely, and making sure that you do not make the same mistakes is your best approach.
I am serious about this - you really really need to pay attention to issues like Happiness and the economy because you will quickly discover in the later missions that ANY problems you allowed to fester early on will then blow up in your face and make it ten times more difficult the deeper into the campaign you get.
I like turtles