The
International Union for Conservation of Nature has ranked
N. granola as vulnerable to extinction. It likely does not occur in more than ten locations and is in decline. It historically occurred in
Kauai,
Maui,
Molokai,
Hawaii and
Oahu but is presently confirmed from Maui, Hawaii, Kauai and Oahu. Major threats include obstruction of natural stream flow and inundation by saline water. ==Growth and lifespan==