If there is no general word covering both meanings, separate words are also fine.
One of the obligations of Shia clerics is to manage ... properties or responsibilities.
I have thought of "abandoned" but that doesn't precisely mean what I wrote in the question title.
Thanks for your contributions! For more elaboration, this is related to a concept in Shia Jurisprudence called "hisba" which refers to obligations and responsibilities that have not been assumed by or are not naturally designated to any specific individual (like taking care of an orphan, an abandoned property, protecting ecosystem, etc) which then have to be taken care of by the clerics. I' looking for a word that can cover all these examples. I am thinking of adjectives in the vein of "stewardless," "ownerless," "un-owned," and "custody-less" etc but one that is probably more common and sound. And oh! I could just think of "unmanaged" or you may suggest a better one! :)