Thinking about this if the diffference in gathering rates is due to gathering skill then learning the gathering technique of the more skilled gatherer would have equal impact to trade as blowing up your island.
If the difference is not learnable and is due to soil and such one would think that the poor island resident would be tempted to relocate to the rich island. Such relocation could go over peacefully or it might cause tensions and border enforcing. But if it goes to enforcement it could go to violence and even threat of violence could be a form of coersion. So already in “We are in our respective islands” we are already in the realm of coersion.
Thinking about this if the diffference in gathering rates is due to gathering skill then learning the gathering technique of the more skilled gatherer would have equal impact to trade as blowing up your island.
If the difference is not learnable and is due to soil and such one would think that the poor island resident would be tempted to relocate to the rich island. Such relocation could go over peacefully or it might cause tensions and border enforcing. But if it goes to enforcement it could go to violence and even threat of violence could be a form of coersion. So already in “We are in our respective islands” we are already in the realm of coersion.