The Rashba"m in the begining of the daf says, if the bor and dus collapse and can't be repaired he loses the path to them. Could you please explain why he speaks about the path, what about the privilege to rebuild the bor and dus themselves ? also where is this rule mentioned?
Noah Zablotsky, Brooklyn, NY
There is an integral difference between the rights to have a tree and the rights to have a Bor. When one owns a tree he actually doesn't own any land; he merely has the right to use the land for his tree. This is why there is a question whether he can replant the tree once it dies. However, when one owns a Bor he actually owns the ground of the Bor. Therefore, it is obvious that he may rebuild the Bor on that ground if it collapses.
With regard to the path, however, the owner of the Bor does not actually own the path. He rather has rights to use it, similar to the rights that the owner of the tree has to the land under the tree ("Shi'abud"). His rights are limited to using the path for access to the Bor. Therefore when the Bor ceases to exist, his rights to use the path to the Bor expire.