Conservation action can be effective even when a population has lost 90% of its individuals

It was with great fascination that I read this paper titled "  Overcoming extinction - Understanding process of recovery in Tibetan Antelope". The paper appeared in the journal Ecosphere in the September 2015 edition. The paper points towards the potential for reversal of the process even in a population plunging towards extinction .The authors affirm that even when the population has entered extinction vortex there is hope.
The paper was authored by C. Leclerc , C. Bellard, G.M Luque and and F.Courchamp. Ecosphere Volume 6, Issue 9 September 2015
Pages 1- 14