Earlier quoted context omitted.
But how is "threatened by extinction" an "extinction vortex"?
When a population is isolated or bottlenecked, there reaches an event horizon where inbreeding causes too manty defects for the population to survive even if one were to curb outside predation/killing. The article points several times to the increasing isolation of the populations and the threats that giving them protected status would require development to take isolation of population in care when developing.
For "vortex" to actually be fitting I'd expect some kind of circular process: perhaps a feedback loop, wherein some process is causing extinction which increasingly leads to more extinction. Like how melting ice leads to warming, which leads to more melting ice, etc, might be fair to call a "warming vortex".