The lions that roam Africa's savannahs have lost as much as 75 per cent of their habitat in the last 50 years as humans overtake their land and the lion population dwindles, according to a new study.

Researchers at Duke University, including prominent conservationist Stuart Pimm, warn that the number of lions across the continent have dropped to as few as 32,000, with populations in West Africa under incredible pressure.

"Lion numbers have declined precipitously in the last century," the study, published Tuesday by the journal Biodiversity and Conservation, reads.

"Given that many now live in small, isolated populations, this trend will continue. The situation in West Africa is particularly dire, with no large population remaining and lions now absent from many of the region's national parks."

Humans move in

Fifty years ago, nearly 100,000 lions roamed across the African continent. In recent years, however, an ever-growing human population has come into the savannah lands to settle and develop. That has both cut down the amount of land lions have to roam, as well as fragmented it, researchers said.

Using satellite imagery, the researchers determined the amount of land now available for lions that remains wild and minimally impacted by human growth. Those lands are rapidly diminishing, and more territory will likely be lost in the next 40 years, the report said.

Five countries in Africa have likely lost their lions since a 2002 study was run, the report said. Only nine countries contain at least 1,000 lions, while Tanzania alone has more than 40 per cent of the continent's lions, it said.

"An obvious caveat is that areas for which we detect little conversion of savannahs to croplands may still suffer human impacts that make them unsuitable for lions," the report said.

"Over-hunting for trophies, poaching — of lions and of their prey species — and conflict with pastoralists may not have any visual signal to satellites. Even where there are low human population densities and areas designated as national parks, there (may) not be lions within them."

The report calls for more mapping and studying to be done to ensure the lions' protection.