Nearly half of Africa's wild lions could be extinct in the next 20 to 40 years, if they're not better protected - according to a new report in the journal Ecology Letters.
Conservationists say the biggest threat to lions are people, and the only way to save them is to fence them off in nature reserves.
Lion populations have taken a big hit over the past 50 years.
Another report "by the NGO LionAid, however, estimated even fewer: 15,000."
As The Guardian's Jeremy Hance writes, "While even 15,000 may sound like a lot when compared to other threatened species, lion populations are spread over more than 20 countries, spanning a geographic area larger than south America."
"Today they survive in small, fragmented pockets," he says. "Looking at a map of historic versus current lion ranges is like viewing a continent submerged by rising seas: only scattered islands remain."
In fact, LionAid says there could be as 645 lions left in Western and Central Africa.
Experts say there are a few reasons for the drop off.
First: people are encroaching more and more into the lions habitat - taking over the land for agriculture, livestock, and to build cities.
"More and more people live in fairly rural areas where there is wildlife, but those people rely on livestock, so they're really coming into conflict often with lions. They just see them as a really dangerous enemy."
Second: there's over-hunting, with people killing lions for sport, trophies or "sham medicine", as Hance puts it.
Third: lions are killed because they're seen as a threat to livestock.
As Hance writes, "some have turned to poisoning lions en-masse. In East Africa, a dangerous pesticide known as Furadan (banned in the EU, Canada, and U.S.) is sprinkled over lion-killed livestock. When the pride returns to feed, they perish agonizingly."
With respect to trophy hunting, he points out "Hunters almost always target mature males--because of their manes."
But he says, "when a top male dies, a pride becomes vulnerable to challengers. If new males take over their first act is to kill any resisting females and all cubs."
Experts say up to 25 lions can end up dying if one adult male is killed.
There are already fenced off reserves in the Serengeti and South Africa's National Parks, which have helped the populations grow.
The report suggests building them throughout Africa, in order to keep lions from being wiped out.
Hunter told the BBC "No one wants to resort to putting any more fences around Africa's marvellous wild areas, but without massive and immediate increases in the commitment to lion conservation, we may have little choice."
Building these kind of reserves isn't cheap - it costs about $500 per square kilometre.
But the report says it's even more expensive to protect lions in unfenced areas - about $2000 per square km.
In closing, Hance writes, "I wouldn't be surprised if in a couple decades our king fell victim to the same fate as the tiger today: down to just a few thousand in protected areas, struggling even there to survive against the rising tide of humanity."