Are they really “the library’s unwitting conservationists”?

According to an article in the June 18, 2018 issue of The Wall Street Journal (“The Bats Help Preserve Old Books, But they Drive Librarians, Well…”, by Patricia Kowsmann), the Joanina Library of the University of Coimbra, Portugal has a colony of small bats (less than 1-1/2 inches long) who come out at night and eat the moths and beetles who could destroy the books in the Library’s collection. The bats bring in hoards of tourists whose presence raises the temperature in the Library, leading to more insects. They also produce pounds of guano which can be damaging to books. So are they really, as they have been called , “the library’s unwitting conservationists”?