The problem is that your island is overgrown, and tribezmen like neat places to live in.
To resolve the issue, please try to perform the following activities:
1. There should be at least one free piece of land around your main building. Try to move it to another place where it can be put. Use the scheme mode when all the buildings are hidden.
2. Move the existing buildings closer to each other: tap on the necessary construction, hold it for a while and drag it to its new position. Then press on the green check icon to complete the move.
3. Your constructions can also be placed in the Inventory: again tap and hold on the building you want, then use the icon with a box and confirm the activity.
4. Try to clear all the bushes and trees.