Coastal populations in southern California face threats due to habitat loss as a result of suburban development. Populations have been highly fragmented due to urbanization, which may lead to genetic differentiation among isolated populations and could threaten overall species viability. Similar species (such as the wrentit and Bewick's wren) which nest in coastal sage scrub (the preferred nesting habitat of coastal cactus wrens) have faced high levels of local extinction.[1][32] California subspecies C. b. sandiegensis was petitioned to be listed as federally endangered in 1990; but was not, due to taxonomic disputes as to whether C. b. sandiegensis was actually distinct from the rest of the cactus wren population.