By the Bais Hora'ah
Q. My neighbor has a tall, aging tree in his front yard, and several gardeners I consulted with unanimously agreed that it is rotting and in danger of falling and hurting a passerby or one of the neighbors. Is my neighbor required to cut down his tree? If he doesn’t, am I allowed to cut it down myself without asking him?
A. The Shulchan Aruch (416:1) states that if a person has a rickety wall or tree that is in danger of falling and hurting the public [or a even a single neighbor – Shu”t HaRashba 3:164, cited by the Beis Yosef], beis din will warn him that if he does not take it down by a certain date and it falls down and injures someone, he will be responsible for damages, under the category of bor (a pit). The deadline is generally thirty days from when beis din issues the warning, but if the danger to the public is imminent, beis din can force him to take action immediately.
The Rema writes that this warning can be issued only by a beis din, not by an ordinary person.
Some poskim say that Rema’s limitation only applies if it is not obvious that the wall is shaky, because the owner can then claim that he didn’t realize it would fall, but if the danger to the public is obvious we do not need beis din to issue the warning (Toras Chaim, Bava Kamma 6b; Divrei Geonim 56:16). Others rule that even if the danger is obvious, the owner can still claim that he didn’t realize he would be responsible for damages caused by the falling tree or wall, so we still need beis din to issue the warning (Perishah 1; Erech Shai, Nesivos 307:1).
[We are only discussing the monetary aspect of this case, but obviously, if there is a chance of people getting injured, the owner has a responsibility to prevent that eventuality even without a warning from beis din.]
The answer to your first question, then, is that if someone might be injured if the tree falls, then your neighbor must remove the tree to eliminate the danger. In contrast, if you are being damaged by circumstances that are typical for properties bordering trees – for instance, the roots are encroaching into your property – you are obligated to take care of the problem, not the owner of the tree (Shulchan Aruch ibid. 155:26-32).
In regard to your second question, the Shulchan Aruch (ibid. 392:1) rules that if a tree must be cut down because it is a danger to the public, and someone cuts it down without first informing the owner, he is not required to reimburse the owner for the value of the tree, because it is considered worthless, since it must be chopped down.
He might owe the owner money for a completely different reason, however. The Gemara states that a person who “stole” another person’s mitzvah is required to reimburse him for it. The poskim deliberate how much a person must pay for stealing a mitzvah. Some say that the dayanim evaluate each case individually, weighing factors such as how much effort goes into performing the mitzvah and how much the person it was stolen from tends to value his mitzvah observance. Others say that there is a standard penalty of ten zehuvim, which, based on current gold prices, is over $550 (Shulchan Aruch ibid. with Sma 1; Shiurei Torah 3:45. According to Sma 88:2 it might be valued at a much higher rate. See Shach, Yoreh Dei’ah 305:1).
Nowadays, beis din does not fine people for stealing mitzvos, but if the person it was stolen from seized money or an object from the mitzvah thief, he may keep it as compensation for the stolen mitzvah.
Returning to our case, it is a mitzvah to prevent damage from befalling others – even if there is no chance of danger to life and limb, only monetary damage (Even Ha’ezel, Nizkei Mammon 5:1; see Dvar Avraham v. 1, 37:35) – so someone who stole that mitzvah would be obligated to pay for it. Since cutting down your neighbor’s tree would be stealing his mitzvah, you should ask him – in a pleasant way – whether he plans to do something about his tree, and inform him that if not, you will cut it down at his expense.