All of these big cats face preassure. Some more than others. However, their preassure comes from the same source, us, humans. Most of the threats that big cats face come in the form of either - hunting, or habitat erosion.
Whereas species such as the Tiger have declined over the last 100 years; the decline of Lions has only been seen recently. Mainly over the last two decades. Unless we step into save the Lion, and their subspecies in the coming years, the Lion is likely to end up the same way as the Tiger.
The decline of Lions is quite worrying. They have disapeared from 16 African countries. And, they have declined a massive 42% in only 21 years. This has led them to be classed as 'vunerable' by conservationists.
Conservationists are working to save the Lion though. And, Lion conservation is working. It has seen Lion species on the rise in many Africa countries, such as Botswana, were the Lion has increased in population by 11%.