How would you make these islands habitable, including having a good atmosphere, without affecting the rest of Earth's ecosystem in undesirable ways?
That's one major difference. A goal of terraforming mars might actually be easier than terraforming remote islands on earth because:
A. It's an isolated system
B. We can afford to fail
Build a port, and have people delivery stuff by boat.
It's not that hard to do
We could stretch out a long hosepipe..
How would you make these islands habitable, including having a good atmosphere, without affecting the rest of Earth's ecosystem in undesirable ways?
That's one major difference. A goal of terraforming mars might actually be easier than terraforming remote islands on earth because:
A. It's an isolated system
B. We can afford to fail