Ironically, their experience is about the opposite of the other Vikings who look to exploit the wealth of others, not that they, the raiders, have no other income but they do look for plunder often enough.
The Icelanders on the other hand are solely dependent on what they can extract from that often marginal land. One wonders how they avoided starvation. My guess is fishing and shell fish. If all else was unavailable, searching for clams, oysters, etc. would be a reliable option. At least I'm guessing it would.