Justification: Melocactus glaucescens has a restricted range (extent of occurrence ca 1,500 km2), the subpopulations are severely fragmented and declining due to several threats. The species was listed as Critically Endangered, but M. Machado (pers. comm. 2011) has found more subpopulations since the species was last assessed. There are potentially more subpopulations but further exploring is needed. Hence, the species now qualifies for Endangered under criterion B1ab(iii).
The species occurs in caatinga and the ecotone with campo rupestre (Chapada Diamantina) element: in the open and between low shrubs of the caatinga on flat or sloping, more or less exposed, crystalline rock outcrops with accumulation of gravel.
Continuing decline in area, extent and/or quality of habitat:
The species is rarely locally collected for candy, medicine and popular belief of the plant having powers to keep away spirits, but this is insignificant. In the past the plant was collected by enthusiasts.